Linked Earth Wiki - User contributions [en]

Main Page

2023-06-24T18:47:55Z

Jeg: point eager users to the LiPDverse instead

[[File:EarthLinked_Banner_blue_NoShadow.jpg|center|440px|alt=LinkedEarthLogo]]

__NOCACHE__

<div style = "text-align:center;">Welcome to the LinkedEarth Wiki!</div>

The LinkedEarth wiki is an [https://earthcube.org EarthCube]-funded platform that:
#enabled the curation of publicly-accessible database by paleoclimate experts, and
#fostered the development of standards, to make paleoclimate data easier to analyze, share, and re-use. 

The [https://www.nsf.gov/awardsearch/showAward?AWD_ID=1541029&HistoricalAwards=false grant] that funded the project has now ended, and this wiki is no longer maintained. If you need access to the most recent version of the LiPD files hosted herein, please go to the [https://lipdverse.org LiPDverse] instead. If you have any questions, please reach out on our [https://discourse.linked.earth Discourse] forum.

==Getting started with LinkedEarth==

<gallery mode = "packed-overlay" widths=150px heights=100px>
File:JoinUsIcon MainPage.png | [http://linked.earth/aboutus/membership/ Join LinkedEarth]
File:GettingStartedIcon MainPage.png | [[Get_Started_with_the_LinkedEarth_wiki | StartUp Guide]]
File:Browse The Wiki.png | [[Special:random | Browse existing pages]]
File:BrowseIcon.png| [[MD982181.Khider.2014 | Browse a curated dataset]]
File:BrowseIcon.png | [[MD982176.Stott.2004 | Browse a curated dataset with Models]]
</gallery>

Several tutorials are also available on our [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel]!

==Community Activities==

Join a [[:Category:Working Group | working group]] (WG) and participate in the discussion about [[Paleoclimate_Data_Standards | paleoclimate data standards]].

'''New''': Each working group has polls waiting for community input. ''You must be logged in to vote.''

In the Linked Earth context, a WG is a self-organized coalition of knowledgeable experts who elaborate and discuss the components of a [[Paleoclimate_Data_Standards | data standard]] for their topic(s) of interest. WGs may be created by any member of the LinkedEarth community. Currently, the LinkedEarth community is organized around {{PAGESINCATEGORY:Working Group}} working groups.

'''To join a WG, do so on your LinkedEarth wiki profile page'''.

<gallery mode = "packed-overlay" widths=150px heights=150px>
File:Open_data_standards_trim.png | [[Paleoclimate Data Standards]]
File:WorkingGroups MainPage Icons.png | [[:Category:Working Group | Join a Working Group]]
File:Ontology_wordcloud.png | [[LinkedEarth Ontology]]
</gallery>

== Contribute Datasets ==

We recommend using the [[Linked Paleo Data | LiPD]] format to get your data on the wiki. The Python [[LiPD Utilities]] allow to create a LiPD from an Excel template, wich can be downloaded [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx here]. For instructions on filling out this template, see the page "[[Creating a LiPD file]]".

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[Creating a LiPD file]]
File:ExcelLogo.png | [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx LiPD Template]
File:AnnotateDatasetImage.png | [[Dataset Tutorial | Upload a LiPD dataset]]
</gallery>

== Working with LiPD Datasets ==

The [[LiPD Utilities]] (available in R, Python, and Matlab) allow to read/write LiPD files, extract and collapse timeseries objects, and filter datasets according to your search criteria. Data analysis packages are currently available in R ([[GeoChronR]]) and Python ([[Pyleoclim]]). A large body of [https://github.com/CommonClimate/PAGES2k_phase2 Matlab code exists already] to analyze the [[PAGES2k]] dataset. If you are unfamiliar with using LiPD files, a good place to start is [[Using LiPD files]].

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[LiPD Utilities]]
File:RLogo.jpeg | [[GeoChronR]]
File:PythonLogo.jpg | [[Pyleoclim]]
</gallery>

==Current State of the Database==

The LinkedEarth Wiki currently contains '''{{PAGESINCATEGORY:Dataset (L)}} datasets''', mostly from the [[PAGES2k]] compilation. We are in the process of adding more Holocene records, as well as >100 deep-sea cores from the LR04 benthic stack compilation. Please contact us if you want to lead a '''data drive''' to flesh it out some more.

=== Dataset Location ===



{{#ask: [[Category:Dataset_(L)]]
| ?CollectedFrom_(L).Coordinates
| ?Name_(L)
| ?ArchiveType
| markercluster=on
| showtitle=off
| zoom=1
| searchmarkers=all
| maxzoom=14
| minzoom=1
| limit=1000
| height=510
| template=LiPDLocation
| format=leaflet
}}

=== Recently Contributed Datasets ===

{{#ask: [[Category:Dataset (L)]]
| ?CollectedFrom (L).CoordinatesFor=LiPD Dataset
| ?ArchiveType
| ?CollectedFrom (L).Coordinates
| mainlabel=-
| limit=10
| format=broadtable
| sort=Modification date
| order = descending
}}

=== Search the Database by Archive===



<gallery mode = "packed-overlay" widths=200px heights=200px>
File:Coral_Archive_200px.jpg | [[:Category:Coral | Coral]]
File:Documents_Archive_200px.jpg | [[:Category:Document | Document]]
File:GlacierIce_Archive_200px.jpg | [[:Category:GlacierIce | Glacier Ice]]
File:Lake_Archive_200px.jpg | [[:Category:LakeSediment | Lake Sediment]]
File:MarineSediment_Archive_200px.jpg | [[:Category:MarineSediment | Marine Sediment]]
File:Mollusk_Archive_200px.jpg | [[:Category:MolluskShells | Mollusk Shells]]
File:Peat_Archive_200px.jpg | [[:Category:Peat | Peat]]
File:Sclerosponge_Archive_200px.jpg | [[:Category:Sclerosponge | Sclerosponge]]
File:Speleothem_Archive_200px.jpg | [[:Category:Speleothem | Speleothem]]
File:Wood_Archive_200px.jpg | [[:Category:Wood | Wood]]
</gallery>

== More about LinkedEarth ==

Website: [http://linked.earth LinkedEarth Website]

Programmatic access to the wiki information: [http://wiki.linked.earth/Dataset_discovery http://wiki.linked.earth/Dataset_discovery]

Social Media: [https://www.facebook.com/LinkedEarth-1018909201501056/?fref=ts Facebook] | [https://twitter.com/Linked_Earth Twitter] | [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel] | [https://github.com/LinkedEarth GitHub]

== Linked Earth Totals ==
''Last changed On: 22 Jul 2020'' Linked Earth contains [http://wiki.linked.earth/Category:Compilation_(L) 6 Compilations], [http://wiki.linked.earth/Category:Dataset_(L) 705 Datasets], [http://wiki.linked.earth/Category:Observation_(L) 4094 Observation] and [http://wiki.linked.earth/Category:Publication_(L) 928 Publications] from [http://wiki.linked.earth/Category:Person_(L) 820 Authors]. The contents of the wiki have been contributed by [http://wiki.linked.earth/Special:ListUsers 196 Scientists] from [http://wiki.linked.earth/Property:University 24 Institutions], organized in [http://wiki.linked.earth/Category:Working_Group 14 Working Groups].

Linked Paleo Data

2021-08-11T03:56:28Z

Jeg: updated links

= LiPD: Linked Paleo Data =

[[File:LiPD Logo.jpg |thumb|400px|right]]

== The LiPD vision ==

Paleoclimate investigators have made a major effort over the past decade to make their data available to the broader community, largely through online archiving systems like the [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data World Data Center for Paleoclimatology] and [http://www.pangaea.de/ Pangaea]. However, there is no agreed-upon data standard for how to store and exchange such data. As the number of records in these archives has grown, making connections manually has thus become more and more challenging, hampering integrative efforts at the very time they should be flourishing. Paleoclimatologists thus need a common tongue to describe their datasets to each other and to machines.

LiPD (Linked Paleo Data) proposes such a common tongue. It is a universally-readable data container that organizes data and metadata in a uniform way, such that they may be web-searchable, and such that a variety of code functionalities may be built and apply instantly to any dataset that observes that standard.

For more details, see [http://www.clim-past-discuss.net/11/4309/2015/cpd-11-4309-2015.html this article].

== LiPD in LinkedEarth ==

LiPD is a convenient way to store and exchange paleoclimate format, and provides the backbone of the LinkedEarth edifice. LiPD is closely aligned with the [[LinkedEarth Ontology]]; changes in one are often reflected in the other (with a small lag).

= Structuring data : the LiPD Way =
== LiPD components ==

[[File:Lipd_structure.png|400px|thumb|right|structure of a lipd file. For an animated presentation see [http://prezi.com/svmit2ys9_d7/?utm_campaign=share&utm_medium=copy&rc=ex0share this prezi]]]

There are 6 possible components to a LiPD dataset. To be considered valid, a LiPD file must observe the structure to the right, and contain basic metadata for at least some of these categories.
=== Root Metadata ===
This describes metadata that applies to the whole dataset. Common examples are:
*Dataset Name
*Investigators
*Link to online dataset
*LiPD version

=== Geographic Metadata ===
Here the the site location is described following the geoJSON standard. This includes:
*Coordinates
*Sitename
*Descriptive location (e.g.,)
**Country
**State
**Province
**Ocean

=== Publication Metadata ===
Describes publications, either traditional or data publications are described following the bibJSON standard. This includes:
*Authors
*Title
*Journal
*DOI
*Year
*URL

=== Funding Metadata ===
Includes information about the research that produced the data were funded, including:
*Funding agency
*Funding grant

=== PaleoData Table ===
This includes all of the measured and inferred paleoenvironmental data - essentially all of the measurements and data from the study that were not used to infer the age. This includes:

====Measurement Tables====
*Column names, units and descriptions
*Interpretation metadata
*Calibration metadata

====Models====
*Methodology used to produce the model results
*Summary table of model output
*Ensemble tables of data produced by the model
*Distribution tables of data produced by the model

=== ChronData Table ===
This mirrors [[Linked_Paleo_Data#PaleoData_Table | PaleoData]] but only includes the data from the study that were used to infer the age of the sequence. This includes:

====Measurement Tables====
*Column names, units and descriptions

====Models====
*Methodology used to produce the model results
*Summary table of model output
*Ensemble tables of data produced by the model
*Distribution tables of data produced by the model

== LiPD implementation ==

LiPD is centered on [http://json-ld.org/ JSON-LD], a [http://www.json.org/ JSON]-based format compliant with the [https://vimeo.com/36752317 Linked Data] paradigm. JavaScript Object Notation (JSON) is an extremely lightweight and flexible way to encode information, and has become the leading format for data exchange on the Web. [http://www.ted.com/talks/tim_berners_lee_on_the_next_web Linked Data] are datasets that observe common rules to be able to be automatically linked through the World Wide Web. A LiPD file (.lpd) is in fact a zipped folder that follows the [https://en.wikipedia.org/wiki/BagIt BagIt] standard:

This includes:
*The BagIt "payload":
**One json-ld file that describes all of the metadata
**Csv tables that include data from all of the tables
*BagIt complementary information, including:
**a “bag-info.txt” file which details metadata for the bag, using colon-separated key/value pairs
**a tag manifest file which lists tag files and their associated MD5 checksums

BagIt is needed to ensure that all the bits on your computer are the same as the bits on the server.

== Working with LiPD data ==

{{See also|GeoChronR|Pyleoclim|LiPD Utilities}}

LiPD was designed so that it can capture much richer sets of (meta)data than ASCII or Excel files, and to have a fixed backbone around which scientific codes can be built.
There is a price to pay for this power: LiPD is undoubtedly more difficult to interact with than a plain text file. Although it is possible to unzip a .lpd file and navigate through the native json-ld and csv files, this is not the best way to harness the power of LiPD files.

This very wiki was designed to allow non-coders to directly access and edit LiPD files. Additionally, a growing number of utilities and software packages can read and write LiPD files, and enable users to readily take advantage of its rich structure:

===List of utilities and software that read and write LiPD===
* [https://github.com/nickmckay/LiPD-utilities LiPD Utilities] in:
**Matlab
**Python
**R
*[https://nickmckay.github.io/GeoChronR/ GeoChronR], an R package for age-modeling and associated ensemble-based workflows (spectral analysis, PCA, correlations, etc.)
*[https://www.cs.colorado.edu/~lizb/cscience.html CSciBox], see [http://linked.earth/featured-partnership-cscience-linkedearth/ this post by Liz Bradley on how LiPD changed how they do science]
*[https://github.com/LinkedEarth/Pyleoclim_util Pyleoclim], a Python package to analyze and visualize paleo data.

== Getting your data into LiPD ==
{{See also|Creating a LiPD file|label 1= creating a LiPD file}}

Once data are in LiPD, and the LiPD file is [http://lipd.net/validator valid], everything is [https://www.youtube.com/watch?v=StTqXEQ2l-Y awesome].

How do you get paleo data into LipD, you ask? This is now very easy thanks to the [http://lipd.net/playground LiPD playground], which enabled basic quality checks along the way. Soon LiPD creation will leverage the [[LinkedEarth_Ontology]] and NOAA's controlled vocabulary. Stay tuned for more updates.

Paleoclimate Data Standards

2020-02-13T19:24:48Z

Jeg: added next steps

= Background =
== What is a standard? ==
[http://www.earthcube.org/document/2015/ecstandardsrecs EarthCube defines] a standard as follows:

a public specification documenting some practice or technology that is adopted and used by a community. [..] There is a continuum starting with any documented practice in some community. If lots of people use a particular documented practice it could be adopted as a best practice. If almost everyone uses some documented practice, then it is a de facto standard.

Notice the emphasis on community and on practice. If only person uses a technical specification, it's not a standard. If it's voted on but not applied in practice, it's worthless as well. Thus, the objective of this EarthCube activity is to propose a standard with broad community appeal and adoption.

== Why do we need standards? ==
Modern life would simply be unlivable without standards. Imagine having to use a separate browser for each web page your visit, or a separate power-transmission system for every appliance you use! You only have to travel to a country that uses a different electric plug than the one your computer and phone employ to appreciate what a nightmare that would be. In science, the ultimate objective of a standard is to make data understandable by others (including machines), and the derived analyses reproducible. Thus, a key objective of LinkedEarth is to promote the development of a community standard for paleoclimate data. Indeed, despite some ad-hoc gatherings among communities of interest over many years, until recently there had never been a concerted effort to produce a standard applicable to all paleoclimate observations. Given the increased importance of synthesis work (e.g. PAGES2k, Shakun et al 2012, Marcott et al 2013, MARGO, others), it is increasingly important that a common solution be found.

= Prior Work =
== Pre-2016 ==
Here is a non-exhaustive list of past discussions that we are aware of:

* [[media: Reporting_Standards_for_Paleoceanographic_PMIP3_Dec2013.docx | PMIP3 Workshop in Corvallis]] (December 2013)
* [http://www.clivar.org/sites/default/files/documents/TriesteReport_nov5.pdf report for the workshop "REPRESENTING AND REDUCING UNCERTAINTIES IN HIGH-RESOLUTION PROXY CLIMATE DATA"] (Trieste, Italy, June 2008)

We welcome any summaries of prior discussions on data standards you may have had at meetings, workshops. To do so, either link to a document that you have uploaded on the wiki or create a new page and list it here.

== LiPD ==
The [[Linked_Paleo_Data|LiPD]] format embodies one part of this solution: it offers a container that can wrap tightly around a wide varieties of paleoclimate [[:Category:Dataset (L)|datasets]], providing a vessel for paleoclimate content. Other formats, of course, would be acceptable; however, there is no viable alternative currently in existence, which is why [[Nicholas_McKay | Nick]] and [[J._Emile-Geay | Julien]] had to go through the trouble of inventing such a format. Another reason to adopt it is that '''there is a growing code ecosystem being developed around LiPD''' in Matlab, R and Python: the [https://github.com/nickmckay/LiPD-utilities LiPD utilities] that allow cross-walk between all kinds of commonly-used formats, [http://nickmckay.github.io/GeoChronR/ GeoChronR] for the analysis of time-uncertain paleo data, and [https://github.com/LinkedEarth/Pyleoclim_util Pyleoclim] to visualize and analyze the data.
Why not just stick with LiPD and call it a day, you ask? Well, LiPD's infinite flexibility is a double-edge sword: it can accommodate all manner of information, but that information may or may not align with community best practices. It is thus '''necessary for the community to decide on such practices'''. In other words, if LiPD provides a field-tested answer to the question: ''how should paleoclimate data be stored?'', it says nothing about '''''what''''' should be stored: that decision is up to the community.

== First workshop on paleoclimate data standards ==
The [[PDS_workshop_2016 | 2016 workshop on paleoclimate data standards]] (PDS workshop, for short) served as a stepping stone to initiate a broader process of community engagement and feedback elicitation, with the goal of generating such a community-vetted standard. The workshop identified a need to '''delineate a set of essential, recommended and desired properties for each dataset'''.
By default, any and all information is desired. A subset of that should be recommended to ensure optimal re-use. Yet a smaller subset of that is '''essential''' in the sense that a paleoclimate data set should not be acceptable without this information (for more details, see the [[PDS_workshop_2016 | PDS workshop page]]). Four additional themes emerged:

=== Cross-Archive Standards ===
Some essential data/metadata are shared among all conceivable archive types:

* '''A table with at least two columns''', one representing time, the other a climate indicator of some sort
* '''Geolocation''': coordinates, polygons, or, in cases where coordinates or polygons cannot be given, general location info
* '''Source''': PI, contributor, or database (first author of publication if published, or some other person who can speak for the dataset if not published/if the first author is no longer in science/etc)
* '''Names''' and '''Units''' of the variables in the dataset

=== Archive-specific standards ===
What is needed to intelligently re-use a marine-annually resolved record could be quite different than what is needed to intelligently re-use an ice core record, for instance. Therefore, these these levels are archive-specific.

=== Legacy vs Modern datasets ===
The group also recognized that standards need to be more stringent for modern datasets than for legacy datasets, for which some (meta)data are sometimes impossible to procure (think: raw radiocarbon dates from a PI now deceased). Thus, for every archive and across archives, there needs to be different set of standards for both kinds.
What constitutes "legacy" data is also open to interpretation, and requires a formal definition (and a vote).

=== Audience and Purpose ===
Finally, it was recognized that all of the above considerations are a function of who is using the data, and for what purpose. As such, it is useful to consider a few science drivers.

= Science Drivers =
One possible way to elaborate a standard is to ask oneself: "What pieces of metadata would I require to reproduce this particular dataset and therefore which one should I provide for my own datasets?" Some of these metadata will be standard across all archives (i.e., geographic coordinates, publication information). Some will be specific to each archive or observation type. See [[:Category:Marine_Sediment_Working_Group | here]] for an example of such discussions on foraminiferal Mg/Ca.

== Querying the datasets ==

Another way to think about the essential/recommended/optional metadata is to think about the kind of queries one would want to enable for their research. For instance, a recent study on [http://linked.earth/wp-content/uploads/2016/01/Khider_AGUFall16.pdf Testing the Millennial-Scale Solar-Climate Connection in the Indo-Pacific Warm Pool] required the following queries and associated metadata:

{| class="wikitable"
|-
! Query || Required Metadata
|-
| SST-sensitive proxies (i.e. Mg/Ca, Uk37 and TEX86) || Needed a property describing the proxy observations as well as a standard to express the concept of Mg/Ca, TEX86 and UK37. This need gave rise to [[:Property:ProxyObservationType_(L)]] and terms in the ontology [[:Category:ProxyObservation_(L)]] to describe these concepts.
|-
| Holocene data (0-10ka) spanning at least 5kyr || Needed a property describing the concept of [[Age]], giving rise to [[:Property:InferredVariableType (L)]]. An ontology for [[:Category:InferredVariable_(L)]] is in progress. It also became obvious that we needed to standardize the way to represent time and the units of time. Furthermore, since the wiki doesn't read the content of the .csv file, some metadata about the values stored in the .csv file were also needed. We therefore created the following properties: [[:Property:HasMinValue (L)]], [[:Property:HasMaxValue (L)]], [[:Property:HasMeanValue (L)]].
|-
| In the IndoPacific Warm Pool || We needed to query the dataset by latitude/longitude.
|}

Other types of basic query include searching for a particular publication, using either the DOI, title, journal, authors, and searching by [[:Category:ProxyArchive_ (L) | archiveType]]. The latter is currently used to obtain the maps under each archive category (for example, [[:Category:MarineSediment | marine sediments]]). Enter the queries you'd like to perform, and the metadata required to perform them.

== Analyzing the datasets ==

Finally, this problem can be approached from a data analysis point-of-view. "Given my interest, what are the required information I would need to perform my analysis?"

For instance, if all is known about a dataset are the geographical coordinates from which the archive was taken, then the only possible analysis is to create a location map of said archive (with or without its nearest neighbor contained in the database). On the other hand, if an age and paleo variable are contained within the PaleoDataTable, the resulting time series can be used for correlation analysis and spectral analysis. However, without the raw age data, it would be impossible to recalibrate the record using updated techniques, limiting its usefulness. To ask the most questions of our datasets, and do the best science, we need them to be as complete as possible.

For the Holocene study, the datasets had to contain the raw radiocarbon measurements for use with [https://cran.r-project.org/web/packages/Bchron/vignettes/Bchron.html Bchron]. [http://linked.earth/doing-science-with-linkedearth/ this blog post] describes how richer and standardized metadata supported the study. This [https://github.com/khider/Holocene-Millennial-Scale-Variability/blob/master/AGU%20Fall%202016/Holocene_MillennialScaleVar.md Jupyter Notebook] integrates code, data and text to walk you through the story. None of this would have been possible without [[Linked_Paleo_Data|LiPD]].

= Process for achieving a paleoclimate data standard=
== Working Groups ==
Attendees of the [[PDS workshop 2016]] proposed that archive-centric [[:Category:Working_Group | working groups]] (WGs; self-assembled coalitions of knowledgeable experts) would be best positioned to elaborate and discuss the components of a data standard for their specific sub-field of paleoclimatology. It is also critical to ensure interoperability between standards to enable longitudinal (multiproxy) investigations.
[[:Category:Working_Group | Working groups]] have been formed and are now being consulted to generate the backbone of a standard, which has been presented to the community at the [http://www.pages-osm.org PAGES OSM meeting] in Zaragoza (May 9-13, 2017).

Current Working Groups:
<DynamicPageList>
category = Working Group
shownamespace = false
</DynamicPageList>

== International Partners ==
This process contributes to the [http://pastglobalchanges.org/ini/int-act/data-stewardship data stewardship initiative] of our [http://www.pastglobalchanges.org/about/general-overview PAGES/Future Earth] partners. Therefore, we are working together with PAGES to reach out to the broadest cross-section of paleoscientists and invite them to contribute to the process. The end goal is a standard to be precisely documented and adopted by LinkedEarth and PAGES. The standard will be implemented in all LinkedEarth activities and proposed for adoption by [http://earthcube.org/ EarthCube], the [https://rd-alliance.org/ Research Data Alliance], the [http://www.esipfed.org/ Federation of Earth Science Information Partners], [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data NOAA WDS-Paleo] and [https://www.pangaea.de/ Pangaea].

== Voting ==
=== Wiki-based voting ===
The first phase of input on data standards (up to October 2017), open only to LinkedEarth members, has leveraged the wiki's polling ability. The results of such polls are summarized in [[PollingStats|Advanced Statistics]].
=== Google Survey ===
The second phase of input, open to all scientists who want to be associated with the Data Standards publication, is available [https://t.co/SUhcYojPJq here] as a Google Survey. It is active until November 10, 2017.

= Standard Publication =
The first iteration of the PaleoClimate reporTing Standard (PaCTS v1.0) was published in ''Paleoceanography and Paleoclimatology'' in December 2019. The paper is open-access and available [https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019PA003632 here]. The standard, at present, is best described as aspirational. A meeting took place at the December 2019 AGU meeting to discuss next steps. If you want to participate, contact [[D._Khider]] or [[J._Emile-Geay]].

Paleoclimate Data Standards

2020-02-13T19:17:58Z

Jeg: fixed typo

Paleoclimate Data Standards

2020-02-13T19:17:41Z

Jeg: fixed formatting

= Background =
== What is a standard? ==
[http://www.earthcube.org/document/2015/ecstandardsrecs EarthCube defines] a standard as follows:

a public specification documenting some practice or technology that is adopted and used by a community. [..] There is a continuum starting with any documented practice in some community. If lots of people use a particular documented practice it could be adopted as a best practice. If almost everyone uses some documented practice, then it is a de facto standard.

Notice the emphasis on community and on practice. If only person uses a technical specification, it's not a standard. If it's voted on but not applied in practice, it's worthless as well. Thus, the objective of this EarthCube activity is to propose a standard with broad community appeal and adoption.

== Why do we need standards? ==
Modern life would simply be unlivable without standards. Imagine having to use a separate browser for each web page your visit, or a separate power-transmission system for every appliance you use! You only have to travel to a country that uses a different electric plug than the one your computer and phone employ to appreciate what a nightmare that would be. In science, the ultimate objective of a standard is to make data understandable by others (including machines), and the derived analyses reproducible. Thus, a key objective of LinkedEarth is to promote the development of a community standard for paleoclimate data. Indeed, despite some ad-hoc gatherings among communities of interest over many years, until recently there had never been a concerted effort to produce a standard applicable to all paleoclimate observations. Given the increased importance of synthesis work (e.g. PAGES2k, Shakun et al 2012, Marcott et al 2013, MARGO, others), it is increasingly important that a common solution be found.

= Prior Work =
== Pre-2016 ==
Here is a non-exhaustive list of past discussions that we are aware of:

* [[media: Reporting_Standards_for_Paleoceanographic_PMIP3_Dec2013.docx | PMIP3 Workshop in Corvallis]] (December 2013)
* [http://www.clivar.org/sites/default/files/documents/TriesteReport_nov5.pdf report for the workshop "REPRESENTING AND REDUCING UNCERTAINTIES IN HIGH-RESOLUTION PROXY CLIMATE DATA"] (Trieste, Italy, June 2008)

We welcome any summaries of prior discussions on data standards you may have had at meetings, workshops. To do so, either link to a document that you have uploaded on the wiki or create a new page and list it here.

== LiPD ==
The [[Linked_Paleo_Data|LiPD]] format embodies one part of this solution: it offers a container that can wrap tightly around a wide varieties of paleoclimate [[:Category:Dataset (L)|datasets]], providing a vessel for paleoclimate content. Other formats, of course, would be acceptable; however, there is no viable alternative currently in existence, which is why [[Nicholas_McKay | Nick]] and [[J._Emile-Geay | Julien]] had to go through the trouble of inventing such a format. Another reason to adopt it is that '''there is a growing code ecosystem being developed around LiPD''' in Matlab, R and Python: the [https://github.com/nickmckay/LiPD-utilities LiPD utilities] that allow cross-walk between all kinds of commonly-used formats, [http://nickmckay.github.io/GeoChronR/ GeoChronR] for the analysis of time-uncertain paleo data, and [https://github.com/LinkedEarth/Pyleoclim_util Pyleoclim] to visualize and analyze the data.
Why not just stick with LiPD and call it a day, you ask? Well, LiPD's infinite flexibility is a double-edge sword: it can accommodate all manner of information, but that information may or may not align with community best practices. It is thus '''necessary for the community to decide on such practices'''. In other words, if LiPD provides a field-tested answer to the question: ''how should paleoclimate data be stored?'', it says nothing about '''''what''''' should be stored: that decision is up to the community.

== First workshop on paleoclimate data standards ==
The [[PDS_workshop_2016 | 2016 workshop on paleoclimate data standards]] (PDS workshop, for short) served as a stepping stone to initiate a broader process of community engagement and feedback elicitation, with the goal of generating such a community-vetted standard. The workshop identified a need to '''delineate a set of essential, recommended and desired properties for each dataset'''.
By default, any and all information is desired. A subset of that should be recommended to ensure optimal re-use. Yet a smaller subset of that is '''essential''' in the sense that a paleoclimate data set should not be acceptable without this information (for more details, see the [[PDS_workshop_2016 | PDS workshop page]]). Four additional themes emerged:

=== Cross-Archive Standards ===
Some essential data/metadata are shared among all conceivable archive types:

* '''A table with at least two columns''', one representing time, the other a climate indicator of some sort
* '''Geolocation''': coordinates, polygons, or, in cases where coordinates or polygons cannot be given, general location info
* '''Source''': PI, contributor, or database (first author of publication if published, or some other person who can speak for the dataset if not published/if the first author is no longer in science/etc)
* '''Names''' and '''Units''' of the variables in the dataset

=== Archive-specific standards ===
What is needed to intelligently re-use a marine-annually resolved record could be quite different than what is needed to intelligently re-use an ice core record, for instance. Therefore, these these levels are archive-specific.

=== Legacy vs Modern datasets ===
The group also recognized that standards need to be more stringent for modern datasets than for legacy datasets, for which some (meta)data are sometimes impossible to procure (think: raw radiocarbon dates from a PI now deceased). Thus, for every archive and across archives, there needs to be different set of standards for both kinds.
What constitutes "legacy" data is also open to interpretation, and requires a formal definition (and a vote).

=== Audience and Purpose ===
Finally, it was recognized that all of the above considerations are a function of who is using the data, and for what purpose. As such, it is useful to consider a few science drivers.

= Science Drivers =
One possible way to elaborate a standard is to ask oneself: "What pieces of metadata would I require to reproduce this particular dataset and therefore which one should I provide for my own datasets?" Some of these metadata will be standard across all archives (i.e., geographic coordinates, publication information). Some will be specific to each archive or observation type. See [[:Category:Marine_Sediment_Working_Group | here]] for an example of such discussions on foraminiferal Mg/Ca.

== Querying the datasets ==

Another way to think about the essential/recommended/optional metadata is to think about the kind of queries one would want to enable for their research. For instance, a recent study on [http://linked.earth/wp-content/uploads/2016/01/Khider_AGUFall16.pdf Testing the Millennial-Scale Solar-Climate Connection in the Indo-Pacific Warm Pool] required the following queries and associated metadata:

{| class="wikitable"
|-
! Query || Required Metadata
|-
| SST-sensitive proxies (i.e. Mg/Ca, Uk37 and TEX86) || Needed a property describing the proxy observations as well as a standard to express the concept of Mg/Ca, TEX86 and UK37. This need gave rise to [[:Property:ProxyObservationType_(L)]] and terms in the ontology [[:Category:ProxyObservation_(L)]] to describe these concepts.
|-
| Holocene data (0-10ka) spanning at least 5kyr || Needed a property describing the concept of [[Age]], giving rise to [[:Property:InferredVariableType (L)]]. An ontology for [[:Category:InferredVariable_(L)]] is in progress. It also became obvious that we needed to standardize the way to represent time and the units of time. Furthermore, since the wiki doesn't read the content of the .csv file, some metadata about the values stored in the .csv file were also needed. We therefore created the following properties: [[:Property:HasMinValue (L)]], [[:Property:HasMaxValue (L)]], [[:Property:HasMeanValue (L)]].
|-
| In the IndoPacific Warm Pool || We needed to query the dataset by latitude/longitude.
|}

Other types of basic query include searching for a particular publication, using either the DOI, title, journal, authors, and searching by [[:Category:ProxyArchive_ (L) | archiveType]]. The latter is currently used to obtain the maps under each archive category (for example, [[:Category:MarineSediment | marine sediments]]). Enter the queries you'd like to perform, and the metadata required to perform them.

== Analyzing the datasets ==

Finally, this problem can be approached from a data analysis point-of-view. "Given my interest, what are the required information I would need to perform my analysis?"

For instance, if all is known about a dataset are the geographical coordinates from which the archive was taken, then the only possible analysis is to create a location map of said archive (with or without its nearest neighbor contained in the database). On the other hand, if an age and paleo variable are contained within the PaleoDataTable, the resulting time series can be used for correlation analysis and spectral analysis. However, without the raw age data, it would be impossible to recalibrate the record using updated techniques, limiting its usefulness. To ask the most questions of our datasets, and do the best science, we need them to be as complete as possible.

For the Holocene study, the datasets had to contain the raw radiocarbon measurements for use with [https://cran.r-project.org/web/packages/Bchron/vignettes/Bchron.html Bchron]. [http://linked.earth/doing-science-with-linkedearth/ this blog post] describes how richer and standardized metadata supported the study. This [https://github.com/khider/Holocene-Millennial-Scale-Variability/blob/master/AGU%20Fall%202016/Holocene_MillennialScaleVar.md Jupyter Notebook] integrates code, data and text to walk you through the story. None of this would have been possible without [[Linked_Paleo_Data|LiPD]].

= Process for achieving a paleoclimate data standard=
== Working Groups ==
Attendees of the [[PDS workshop 2016]] proposed that archive-centric [[:Category:Working_Group | working groups]] (WGs; self-assembled coalitions of knowledgeable experts) would be best positioned to elaborate and discuss the components of a data standard for their specific sub-field of paleoclimatology. It is also critical to ensure interoperability between standards to enable longitudinal (multiproxy) investigations.
[[:Category:Working_Group | Working groups]] have been formed and are now being consulted to generate the backbone of a standard, which has been presented to the community at the [http://www.pages-osm.org PAGES OSM meeting] in Zaragoza (May 9-13, 2017).

Current Working Groups:
<DynamicPageList>
category = Working Group
shownamespace = false
</DynamicPageList>

== International Partners ==
This process contributes to the [http://pastglobalchanges.org/ini/int-act/data-stewardship data stewardship initiative] of our [http://www.pastglobalchanges.org/about/general-overview PAGES/Future Earth] partners. Therefore, we are working together with PAGES to reach out to the broadest cross-section of paleoscientists and invite them to contribute to the process. The end goal is a standard to be precisely documented and adopted by LinkedEarth and PAGES. The standard will be implemented in all LinkedEarth activities and proposed for adoption by [http://earthcube.org/ EarthCube], the [https://rd-alliance.org/ Research Data Alliance], the [http://www.esipfed.org/ Federation of Earth Science Information Partners], [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data NOAA WDS-Paleo] and [https://www.pangaea.de/ Pangaea].

== Voting ==
=== Wiki-based voting ===
The first phase of input on data standards (up to October 2017), open only to LinkedEarth members, has leveraged the wiki's polling ability. The results of such polls are summarized in [[PollingStats|Advanced Statistics]].
=== Google Survey ===
The second phase of input, open to all scientists who want to be associated with the Data Standards publication, is available [https://t.co/SUhcYojPJq here] as a Google Survey. It is active until November 10, 2017.

= Standard Publication =
The first iteration of the PaleoClimate repoTing Standard (PaCTS v1.0) was published in ''Paleoceanography and Paleoclimatology'' in December 2019. The paper is open-access and available [https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019PA003632 here].

Paleoclimate Data Standards

2020-02-13T19:17:19Z

Jeg: replaced publication plan with actual publication

= Background =
== What is a standard? ==
[http://www.earthcube.org/document/2015/ecstandardsrecs EarthCube defines] a standard as follows:

a public specification documenting some practice or technology that is adopted and used by a community. [..] There is a continuum starting with any documented practice in some community. If lots of people use a particular documented practice it could be adopted as a best practice. If almost everyone uses some documented practice, then it is a de facto standard.

Notice the emphasis on community and on practice. If only person uses a technical specification, it's not a standard. If it's voted on but not applied in practice, it's worthless as well. Thus, the objective of this EarthCube activity is to propose a standard with broad community appeal and adoption.

== Why do we need standards? ==
Modern life would simply be unlivable without standards. Imagine having to use a separate browser for each web page your visit, or a separate power-transmission system for every appliance you use! You only have to travel to a country that uses a different electric plug than the one your computer and phone employ to appreciate what a nightmare that would be. In science, the ultimate objective of a standard is to make data understandable by others (including machines), and the derived analyses reproducible. Thus, a key objective of LinkedEarth is to promote the development of a community standard for paleoclimate data. Indeed, despite some ad-hoc gatherings among communities of interest over many years, until recently there had never been a concerted effort to produce a standard applicable to all paleoclimate observations. Given the increased importance of synthesis work (e.g. PAGES2k, Shakun et al 2012, Marcott et al 2013, MARGO, others), it is increasingly important that a common solution be found.

= Prior Work =
== Pre-2016 ==
Here is a non-exhaustive list of past discussions that we are aware of:

* [[media: Reporting_Standards_for_Paleoceanographic_PMIP3_Dec2013.docx | PMIP3 Workshop in Corvallis]] (December 2013)
* [http://www.clivar.org/sites/default/files/documents/TriesteReport_nov5.pdf report for the workshop "REPRESENTING AND REDUCING UNCERTAINTIES IN HIGH-RESOLUTION PROXY CLIMATE DATA"] (Trieste, Italy, June 2008)

We welcome any summaries of prior discussions on data standards you may have had at meetings, workshops. To do so, either link to a document that you have uploaded on the wiki or create a new page and list it here.

== LiPD ==
The [[Linked_Paleo_Data|LiPD]] format embodies one part of this solution: it offers a container that can wrap tightly around a wide varieties of paleoclimate [[:Category:Dataset (L)|datasets]], providing a vessel for paleoclimate content. Other formats, of course, would be acceptable; however, there is no viable alternative currently in existence, which is why [[Nicholas_McKay | Nick]] and [[J._Emile-Geay | Julien]] had to go through the trouble of inventing such a format. Another reason to adopt it is that '''there is a growing code ecosystem being developed around LiPD''' in Matlab, R and Python: the [https://github.com/nickmckay/LiPD-utilities LiPD utilities] that allow cross-walk between all kinds of commonly-used formats, [http://nickmckay.github.io/GeoChronR/ GeoChronR] for the analysis of time-uncertain paleo data, and [https://github.com/LinkedEarth/Pyleoclim_util Pyleoclim] to visualize and analyze the data.
Why not just stick with LiPD and call it a day, you ask? Well, LiPD's infinite flexibility is a double-edge sword: it can accommodate all manner of information, but that information may or may not align with community best practices. It is thus '''necessary for the community to decide on such practices'''. In other words, if LiPD provides a field-tested answer to the question: ''how should paleoclimate data be stored?'', it says nothing about '''''what''''' should be stored: that decision is up to the community.

== First workshop on paleoclimate data standards ==
The [[PDS_workshop_2016 | 2016 workshop on paleoclimate data standards]] (PDS workshop, for short) served as a stepping stone to initiate a broader process of community engagement and feedback elicitation, with the goal of generating such a community-vetted standard. The workshop identified a need to '''delineate a set of essential, recommended and desired properties for each dataset'''.
By default, any and all information is desired. A subset of that should be recommended to ensure optimal re-use. Yet a smaller subset of that is '''essential''' in the sense that a paleoclimate data set should not be acceptable without this information (for more details, see the [[PDS_workshop_2016 | PDS workshop page]]). Four additional themes emerged:

=== Cross-Archive Standards ===
Some essential data/metadata are shared among all conceivable archive types:

* '''A table with at least two columns''', one representing time, the other a climate indicator of some sort
* '''Geolocation''': coordinates, polygons, or, in cases where coordinates or polygons cannot be given, general location info
* '''Source''': PI, contributor, or database (first author of publication if published, or some other person who can speak for the dataset if not published/if the first author is no longer in science/etc)
* '''Names''' and '''Units''' of the variables in the dataset

=== Archive-specific standards ===
What is needed to intelligently re-use a marine-annually resolved record could be quite different than what is needed to intelligently re-use an ice core record, for instance. Therefore, these these levels are archive-specific.

=== Legacy vs Modern datasets ===
The group also recognized that standards need to be more stringent for modern datasets than for legacy datasets, for which some (meta)data are sometimes impossible to procure (think: raw radiocarbon dates from a PI now deceased). Thus, for every archive and across archives, there needs to be different set of standards for both kinds.
What constitutes "legacy" data is also open to interpretation, and requires a formal definition (and a vote).

=== Audience and Purpose ===
Finally, it was recognized that all of the above considerations are a function of who is using the data, and for what purpose. As such, it is useful to consider a few science drivers.

= Science Drivers =
One possible way to elaborate a standard is to ask oneself: "What pieces of metadata would I require to reproduce this particular dataset and therefore which one should I provide for my own datasets?" Some of these metadata will be standard across all archives (i.e., geographic coordinates, publication information). Some will be specific to each archive or observation type. See [[:Category:Marine_Sediment_Working_Group | here]] for an example of such discussions on foraminiferal Mg/Ca.

== Querying the datasets ==

Another way to think about the essential/recommended/optional metadata is to think about the kind of queries one would want to enable for their research. For instance, a recent study on [http://linked.earth/wp-content/uploads/2016/01/Khider_AGUFall16.pdf Testing the Millennial-Scale Solar-Climate Connection in the Indo-Pacific Warm Pool] required the following queries and associated metadata:

{| class="wikitable"
|-
! Query || Required Metadata
|-
| SST-sensitive proxies (i.e. Mg/Ca, Uk37 and TEX86) || Needed a property describing the proxy observations as well as a standard to express the concept of Mg/Ca, TEX86 and UK37. This need gave rise to [[:Property:ProxyObservationType_(L)]] and terms in the ontology [[:Category:ProxyObservation_(L)]] to describe these concepts.
|-
| Holocene data (0-10ka) spanning at least 5kyr || Needed a property describing the concept of [[Age]], giving rise to [[:Property:InferredVariableType (L)]]. An ontology for [[:Category:InferredVariable_(L)]] is in progress. It also became obvious that we needed to standardize the way to represent time and the units of time. Furthermore, since the wiki doesn't read the content of the .csv file, some metadata about the values stored in the .csv file were also needed. We therefore created the following properties: [[:Property:HasMinValue (L)]], [[:Property:HasMaxValue (L)]], [[:Property:HasMeanValue (L)]].
|-
| In the IndoPacific Warm Pool || We needed to query the dataset by latitude/longitude.
|}

Other types of basic query include searching for a particular publication, using either the DOI, title, journal, authors, and searching by [[:Category:ProxyArchive_ (L) | archiveType]]. The latter is currently used to obtain the maps under each archive category (for example, [[:Category:MarineSediment | marine sediments]]). Enter the queries you'd like to perform, and the metadata required to perform them.

== Analyzing the datasets ==

Finally, this problem can be approached from a data analysis point-of-view. "Given my interest, what are the required information I would need to perform my analysis?"

For instance, if all is known about a dataset are the geographical coordinates from which the archive was taken, then the only possible analysis is to create a location map of said archive (with or without its nearest neighbor contained in the database). On the other hand, if an age and paleo variable are contained within the PaleoDataTable, the resulting time series can be used for correlation analysis and spectral analysis. However, without the raw age data, it would be impossible to recalibrate the record using updated techniques, limiting its usefulness. To ask the most questions of our datasets, and do the best science, we need them to be as complete as possible.

For the Holocene study, the datasets had to contain the raw radiocarbon measurements for use with [https://cran.r-project.org/web/packages/Bchron/vignettes/Bchron.html Bchron]. [http://linked.earth/doing-science-with-linkedearth/ this blog post] describes how richer and standardized metadata supported the study. This [https://github.com/khider/Holocene-Millennial-Scale-Variability/blob/master/AGU%20Fall%202016/Holocene_MillennialScaleVar.md Jupyter Notebook] integrates code, data and text to walk you through the story. None of this would have been possible without [[Linked_Paleo_Data|LiPD]].

= Process for achieving a paleoclimate data standard=
== Working Groups ==
Attendees of the [[PDS workshop 2016]] proposed that archive-centric [[:Category:Working_Group | working groups]] (WGs; self-assembled coalitions of knowledgeable experts) would be best positioned to elaborate and discuss the components of a data standard for their specific sub-field of paleoclimatology. It is also critical to ensure interoperability between standards to enable longitudinal (multiproxy) investigations.
[[:Category:Working_Group | Working groups]] have been formed and are now being consulted to generate the backbone of a standard, which has been presented to the community at the [http://www.pages-osm.org PAGES OSM meeting] in Zaragoza (May 9-13, 2017).

Current Working Groups:
<DynamicPageList>
category = Working Group
shownamespace = false
</DynamicPageList>

== International Partners ==
This process contributes to the [http://pastglobalchanges.org/ini/int-act/data-stewardship data stewardship initiative] of our [http://www.pastglobalchanges.org/about/general-overview PAGES/Future Earth] partners. Therefore, we are working together with PAGES to reach out to the broadest cross-section of paleoscientists and invite them to contribute to the process. The end goal is a standard to be precisely documented and adopted by LinkedEarth and PAGES. The standard will be implemented in all LinkedEarth activities and proposed for adoption by [http://earthcube.org/ EarthCube], the [https://rd-alliance.org/ Research Data Alliance], the [http://www.esipfed.org/ Federation of Earth Science Information Partners], [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data NOAA WDS-Paleo] and [https://www.pangaea.de/ Pangaea].

== Voting ==
=== Wiki-based voting ===
The first phase of input on data standards (up to October 2017), open only to LinkedEarth members, has leveraged the wiki's polling ability. The results of such polls are summarized in [[PollingStats|Advanced Statistics]].
=== Google Survey ===
The second phase of input, open to all scientists who want to be associated with the Data Standards publication, is available [https://t.co/SUhcYojPJq here] as a Google Survey. It is active until November 10, 2017.

= Standard Publication =

The first iteration of the PaleoClimate repoTing Standard (PaCTS v1.0) was published in ''Paleoceanography and Paleoclimatology'' in December 2019. The paper is open-access and available [https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019PA003632 here].

PaCTS v1.0

2019-06-20T05:47:58Z

Jeg: added minimal content for the road ahead

This page describes the first version of PaCTS (Paleoclimate Community reporTing Standard).

==Background==

This page describes PaCTS v1.0, which represents the first attempt by the paleoclimate community to [[Paleoclimate Data Standards | standardize]] the reporting of paleoclimate data. To do so, the community organized itself in [[:Category:Working Group | working groups]] centered around the main [[:Category: ProxyArchive (L) | proxy archives]]. To see detailed discussions about how the standards evolved, see the current working groups (shortcut on the left).

The recommendation follows a vote on this platform, the [https://twitter.com/Linked_Earth LinkedEarth twitter account], and a survey distributed to the community through various platforms (e.g., listservs, PAGES network).

==PaCTS v1.0==

Each property is either deemed essential (without which the record can't be reused), recommended (necessary to reuse the record optimally), and desired.

In this context a legacy dataset is defined as a dataset that has not been contributed by the original author (see [[Cross Archive Metadata | here]] for details).

===Cross Archive Metadata===

See the discussion in the [[Cross Archive Metadata | cross-archive metadata working group page]].

==== Datasets ====

{| class= "wikitable"
|-
|+Table 1: Recommendation for cross-archive metadata
|-
! Question || New datasets || Legacy datasets
|-
| contributor || Essential || Essential
|-
| latitude || Essential || Essential
|-
| longitude || Essential || Essential
|-
| altitude || Essential || Essential
|-
| site name || Essential || Essential
|-
| dataset version || Essential || Recommended
|-
| any publication information || Essential || Essential
|-
| publication authors || Essential || Essential
|-
| publication year || Essential || Essential
|-
| publication title || Essential || Essential
|-
| publication doi || Essential || Essential
|-
| publication journal || Essential || Essential
|-
| funding information || Desired || Desired
|-
| funding principal investigator || Desired || Desired
|-
| funding agency || Desired || Desired
|-
| funding country || Desired || Desired
|-
| funding grant || Desired || Desired
|-
| any paleodata information || Essential || Essential
|-
| any chrondata information || Essential || Essential
|-
| depth/distance/position in the archive || Essential || Essential
|-
| information about how depth is transformed to age || Essential || Recommended
|-
| sample thickness || Essential || Recommended
|-
| original measurements || Essential || Essential
|-
| units || Essential || Essential
|-
| analysis date || Recommended || Desired
|-
| any additional data measured along the primary data of interest || Recommended || Recommended
|-
| interpretation || Recommended || Recommended
|-
| calibrated values || Essential || Recommended
|-
| calibration model || Essential || Recommended
|-
| calibration reference || Recommended || Recommended
|-
| physical sample name || Recommended || Desired
|-
| physical sample IGSN || Recommended || Desired
|-
| physical sample collection method || Recommended || Desired
|-
| instrument type || Essential || Recommended
|-
| laboratory name || Recommended || Desired
|-
| analytical method || Essential || Recommended
|-
| method reference || Recommended || Desired
|}

==== Compilations ====

{| class= "wikitable"
|-
|+Table 2: Recommendation for compilations
|-
! Question || New compilations || Legacy compilations
|-
| compilation name || Essential || Essential
|-
| compilation authors || Essential || Essential
|-
| funding agency || Desired || Desired
|-
| funding principal investigator || Desired || Desired
|-
| funding grant number || Desired || Desired
|-
| funding country || Desired || Desired
|-
| model used to compile data || Essential || Essential
|-
| compilation date || Essential || Recommended
|-
| compilation version || Essential || Recommended
|-
| compilation change log || Essential || Recommended
|-
| publication title || Essential || Essential
|-
| publication authors || Essential || Essential
|-
| publication year || Essential || Essential
|-
| publication journal || Essential || Essential
|-
| publication doi || Essential || Essential
|-
| publication from previous work || Essential || Recommended
|-
| unique identifier to the time series used in the compilation || Essential || Recommended
|}

===Historical Documents===

To see the discussion on historical documents, see this [[:Category:Historical Documents Working Group | page]]

{| class= "wikitable"
|-
|+Recommendation for historical data
|-
! Question || New datasets || Legacy datasets
|-
| URL to external Pages (scans, pages) || Recommended || Recommended
|-
| quote ID for later reference || Essential || Recommended
|-
| reference to quote source || Essential || Essential
|-
| pages from which the quote is extracted from || Recommended || Recommended
|-
| language of the quote (or its translation) || Recommended || Recommended
|-
| quote's protolanguage || Recommended || Recommended
|-
| quote || Essential || Essential
|-
| quote's license || Recommended || Recommended
|-
| quote's doi || Essential || Recommended
|}

===Ice Cores===

See the discussion on the ice cores working group [[:Category:Ice Cores Working Group | page]].

{| class= "wikitable"
|-
|+Recommendation for ice cores
|-
! Question || New datasets || Legacy datasets
|-
| possible melt in transport || Essential || Essential
|-
| depth of any melt layer || Essential || Essential
|-
| depth of ash layer || Essential || NA
|-
| all proxy observations determined in the core || Essential || Essential
|-
| continous vs discrete sampling || Essential || Essential
|-
| coring techniques || Essential || Recommended
|-
| core cutting techniques || Recommended || Desired
|-
| core storage conditions || Recommended || Desired
|-
| whether the bedrock has been reached || Recommended || Desired
|-
| borehole temperatures || Recommended || Desired
|-
| depth and composition of any organic material || Recommended || Desired
|-
| if available, any snowpit information from the same location || Recommended || Desired
|-
| core densities || Essential || Desired
|-
| depth of brittle ice || Essential || Desired
|-
| depth of firn/ice transition || Recommended || Recommended
|-
| presence of elongated bubbles || Recommended || Recommended
|}

===Lake Sediments===

See the discussion on the lake sediments working group [[:Category:Lake Sediments Working Group | page]]

==== Accumulation rate ====

{| class= "wikitable"
|-
|+Recommendation for accumulation rate on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| accumulation rate || Essential || Essential
|-
| thickness || Essential || Essential
|-
| density || Essential || Essential
|-
| units || Essential || Essential
|-
| chronological constraints || Essential || Essential
|-
| accumulation rate type || Essential || Essential
|-
| method || Essential || Essential
|-
| pretreatment method || Recommended || Recommended
|-
| interpretation || Recommended || Recommended
|}

==== Compound Specific Isotopes ====

{|class= "wikitable"
|-
|+Recommendation for compound specific isotopes on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| sample depth || Essential || Essential
|-
| compound(s) analyzed || Essential || Essential
|-
| source of compound in sediments || Essential || Essential
|-
| isotope measured || Essential || Essential
|-
| interpretation || Recommended || Recommended
|}

==== Density ====

{|class= "wikitable"
|-
|+Recommendation for density measurements on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| density name (e.g., wet bulk density) || Essential || Essential
|-
| water content/porosity || Recommended || Recommended
|-
| original measurements || Essential || Essential
|-
| units || Essential || Essential
|-
| density type (inferred or measured) || Essential || Recommended
|-
| method (e.g. direct sampling) || Essential || Essential
|-
| interpretation || Recommended || Recommended
|}

==== Imagery data ====

{|class= "wikitable"
|-
|+Recommendation for imagery data on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| reflectance or transmittance (by wavelength) || Essential || Essential
|-
| units || Essential || Essential
|-
| original measurements || Essential || Essential
|-
| post acquisition processing methods || Essential || Recommended
|-
| data reduction methods (peak or trough area method) || Recommended || Recommended
|-
| pretreatment methods || Essential || Recommended
|-
| analytical method || Essential || Recommended
|-
| analytical instrument || Recommended || Recommended
|-
| interpretation || Recommended || Desired
|}

==== Magnetic data ====

{|class= "wikitable"
|-
|+Recommendation for magnetic data on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| position of the core within the lake basin || Essential || Essential
|-
| ancillary data about the archive (carbonate and organic content) || Recommended || Recommended
|-
| flag that the signal recorded hasn't been altered by geochemisty || Essential || Recommended
|}

==== Mineralogy ====

{|class= "wikitable"
|-
|+Recommendation for mineralogy on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| relative abundance (by mineral) || Essential || Essential
|-
| units || Essential || Essential
|-
| original measurements || Essential || Recommended
|-
| mineralogy type || Recommended || Recommended
|-
| pretreatment method || Essential || Recommended
|-
| analytical method || Essential || Essential
|-
| analytical instrument || Recommended || Recommended
|-
| interpretation || Recommended || Recommended
|}

==== Multiple cores ====

{|class= "wikitable"
|-
|+Recommendation for multiple cores
|-
! Question || New datasets || Legacy datasets
|-
| mid-point depth (core depth) || Essential || Recommended
|-
| mid-point depth (composite depth) || Essential || Essential
|-
| thickness || Essential || Recommended
|-
| information about the relationship between core depth and composite depth || Essential || Recommended
|}

====Particle size ====

{| class= "wikitable"
|-
|+Recommendation for particle size on lake sediment cores
|-
! Question || New datasets || Legacy datasets
|-
| % volume or mass by grain size class/interval || Essential || Essential
|-
| units || Essential || Essential
|-
| original measurements || Essential || Recommended
|-
| summary statistics used to characterize distribution || Recommended || Recommended
|-
| particle size type || Essential || Recommended
|-
| pretreatment methods || Essential || Recommended
|-
| anlytical method (e.g. laser diffraction) || Essential || Recommended
|-
| analytical instrument || Recommended || Recommended
|-
| interpretation || Recommended || Recommended
|}

===Marine Sediments===

See the discussion on the marine sediments working group [[:Category:Marine Sediment Working Group | page]].

==== General ====

{|class= "wikitable"
|-
|+Recommendation for marine sediments
|-
! Question || New datasets || Legacy datasets
|-
| gear type for collection of the archive || Recommended || Recommended
|-
| volume of sediment analyzed || Recommended || Recommended
|}

==== Alkenones ====

{|class= "wikitable"
|-
|+Recommendation for alkenones on marine sediments
|-
! Question || New datasets || Legacy datasets
|-
| index value || Essential || Essential
|-
| method of sediment extraction || Essential || Essential
|-
| raw peak areas || Recommended || Recommended
|-
| alkenone concentration || Essential || Recommended
|-
| C37-C39 compound concentration || Essential || Recommended
|-
| analytical method (retention time vs mass spec, LOD, LOQ) || Essential || Essential
|}

==== Bulk sediment geochemistry ====

{|class= "wikitable"
|-
|+Recommendation for bulk sediment geochemistry on marine sediments
|-
! Question || New datasets || Legacy datasets
|-
| sample pretreatment || Essential || Recommended
|}

==== GDGTs ====

{|class= "wikitable"
|-
|+Recommendation for GDGTs measurements on marine sediments
|-
! Question || New datasets || Legacy datasets
|-
| GDGT index || Essential || Essential
|-
| core lipids or IPLs analyzed || Essential || Essential
|-
| method of sediment extration || Essential || Recommended
|-
| raw peak areas || Recommended || Recommended
|-
| definition of the index used || Essential || Essential
|}

==== Micropaleontology ====

{|class= "wikitable"
|-
|+Recommendation for micropaleontological determination on marine sediments
|-
! Question || New datasets || Legacy datasets
|-
| raw counts || Essential || Essential
|-
| minimum number of speciments || Essential || Recommended
|-
| size fraction || Essential || Essential
|-
| seasonality || Recommended || Recommended
|-
| habitat depth || Essential || Recommended
|-
| training set || Recommended || Recommended
|}

==== Foraminifera ====

===== Geochemistry =====

{|class= "wikitable"
|-
|+Recommendation for geochemical measurements on foraminifera
|-
! Question || New datasets || Legacy datasets
|-
| Genus || Essential || Essential
|-
| Species || Essential || Essential
|-
| taxonomy being followed || Essential || Recommended
|}

===== Stable Isotopes =====

{|class= "wikitable"
|-
|+Recommendation for stable isotopes measurements on foraminifera
|-
! Question || New datasets || Legacy datasets
|-
| cleaning methodology || Essential || Essential
|-
| cleaning methodology reference || Recommended || Recommended
|-
| number of specimens utilized by sample || Essential || Essential
|-
| size fraction || Essential || Essential
|-
| method of sediment disintegration and washing || Essential || Recommended
|-
| equilibirum offset || Essential || Recommended
|-
| seasonality || Recommended || Recommended
|-
| habitat depth || Essential || Recommended
|-
| standard (e.g. VPDB) || Essential || Essential
|-
| contamination indicators || Recommended || Recommended
|}

===== Trace elements =====

{|class= "wikitable"
|-
|+Recommendation for trace elements measurements on foraminifera
|-
! Question || New datasets || Legacy datasets
|-
| cleaning methodology || Essential || Essential
|-
| cleaning methodology reference || Recommended || Recommended
|-
| number of specimens utilized per sample || Essential || Essential
|-
| size fraction || Essential || Essential
|-
| method of sediment disintegration and washing || Essential || Essential
|-
| correction || Essential || Essential
|-
| seasonality || Recommended || Recommended
|-
| habitat depth || Recommended || Recommended
|-
| contamination indicators || Essential || Recommended
|-
| standard || Essential || Essential
|}

===== Boron isotopes =====

{|class= "wikitable"
|-
|+Recommendation for boron isotopes measurements on foraminifera
|-
! Question || New datasets || Legacy datasets
|-
| separation method || Essential || Essential
|-
| analysis method || Essential || Essential
|-
| sample size (ng of boron analyzed) || Essential || Essential
|-
| standard || Essential || Essential
|-
| water depth (benthic foraminifera) || Essential || Recommended
|}

===MARPA===

See the discussion on the MARPA working group [[:Category:MARPA Working Group | page]]. Please note that most of the properties described in this working group formed the basis for the cross-archive recommendations.

{|class= "wikitable"
|-
|+Recommendation for MARPA archives
|-
! Question || New datasets || Legacy datasets
|-
| interpolated chronology || Essential || Essential
|-
| X-ray pictures || Recommended || Recommended
|}

===Speleothems===

See the discussion on the speleothems working group [[:Category:Speleothem Working Group | page]].

==== Cave ====

{|class= "wikitable"
|-
|+Recommendation for cave metadata for speleothems archives
|-
! Question || New datasets || Legacy datasets
|-
| cave geology || Essential || Recommended
|-
| rock age || Essential || Recommended
|}

==== Modern cave conditions ====

{|class= "wikitable"
|-
|+Recommendation for modern cave conditions metadata for speleothems archives
|-
! Question || New datasets || Legacy datasets
|-
| soil thickness || Recommended || Recommended
|-
| vegetation type || Recommended || Recommended
|-
| karst residence time || Recommended || Recommended
|-
| karst transit time distribution || Recommended || Recommended
|-
| karst porosity || Recommended || Recommended
|-
| rock overburden thickness || Recommended || Recommended
|-
| flow route type || Recommended || Recommended
|-
| in-cave temperature || Essential || Recommended
|-
| in-cave humidity || Essential || Recommended
|-
| in-cave pCO2 || Essential || Recommended
|-
| in-cave drip rate || Recommended || Recommended
|-
| in-cave drip chemistry || Recommended || Recommended
|}

==== Physical Sample ====

{|class= "wikitable"
|-
|+Recommendation for physical samples metadata for speleothems archives
|-
! Question || New datasets || Legacy datasets
|-
| distance from cave entrance || Recommended || Recommended
|-
| thickness of overlying bedrock over the speleothem || Recommended || Recommended
|-
| speleothem type (e.g. candlestick, flowstone) || Essential || Recommended
|-
| drip type || Recommended || Recommended
|-
| type of measurements available || Essential || Recommended
|}

==== Sample data ====

{|class= "wikitable"
|-
|+Recommendation for sample data metadata for speleothems archives
|-
! Question || New datasets || Legacy datasets
|-
| thickness of analyzed sample || Essential || Essential
|-
| evidence of equilibrium || Essential || Recommended
|-
| isotope standards || Essential || Essential
|-
| correction made for aragonite || Essential || Recommended
|}

===Trees===
See the discussion on the trees working group [[:Category:Trees Working Group | page]].

{|class= "wikitable"
|-
|+Recommendation for trees metadata
|-
! Question || New datasets || Legacy datasets
|-
| missing ring || Essential || Essential
|-
| taxonomy (genus/species) || Essential || Essential
|-
| tree height || Recommended || Recommended
|-
| tree diameter || Essential || Essential
|-
| soil description || Recommended || Recommended
|-
| soil depth || Recommended || Recommended
|-
| bedrock description || Desired || Desired
|-
| knots || Desired || Desired
|-
| ring count || Essential || Essential
|-
| average ring width || Essential || Essential
|-
| number of unmeasured innner rings || Essential || Desired
|-
| number of unmeasured outer rings || Essential || Desired
|-
| missing heartwood rings to pith || Essential || Recommended
|-
| missing heartwood rings to pith foundation || Essential || Recommended
|-
| number of sapwood rings || Essential || Recommended
|-
| last ring under bark || Recommended || Recommended
|-
| missing sapwood rings to bark || Recommended || Desired
|-
| missing sapwood rings to bark foundation || Recommended || Desired
|-
| pith year || Essential || Essential
|-
| death year || Essential || Essential
|}

==== Detrending ====

{|class= "wikitable"
|-
|+Recommendation for detrending of trees records
|-
! Question || New datasets || Legacy datasets
|-
| software used || Essential || Essential
|-
| version used || Essential || Recommended
|-
| detrending method name (e.g. polynomial, exponential) || Essential || Essential
|-
| method parameters || Essential || Recommended
|}

==== Stable isotopes ====

{|class= "wikitable"
|-
|+Recommendation for stables isotopes measurements on trees
|-
! Question || New datasets || Legacy datasets
|-
| whether or not a chronology was established || Essential || Essential
|-
| if there is no chronology (or it is floating) how was age established || Essential || Essential
|-
| if it is a tropical tree how was the age model established || Essential || Essential
|-
| were samples pooled or are samples single ring/single tree measurements || Essential || Essential
|-
| what portion of the ring was analyzed || Essential || Essential
|-
| whether samples were pre-treated by conversion to alpha cellulose, holo cellulose or left unprocessed || Essential || Essential
|-
| pretreatment method || Essential || Essential
|-
| analysis date || Recommended || Desired
|-
| isotope measured || Essential || Essential
|-
| 13C data corrected for Seuss effect || Essential || Essential
|-
| correction used || Essential || Essential
|}

===Chronologies===

To know more about the standardization process, check the chronologies working group [[:Category:Chronologies Working Group | page]].

==== Absolute chronologies ====

===== Lead =====

{|class= "wikitable"
|-
|+Recommendation for chronologies based on lead isotopes
|-
! Question || New datasets || Legacy datasets
|-
| calculated excess 210Pb values || Essential || Essential
|-
| 226Ra || Essential || Recommended
|-
| total 210Pb || Essential || Essential
|-
| salt correction applied || Essential || Recommended
|-
| porosity || Recommended || Recommended
|-
| depth/position || Essential || Essential
|-
| sample thickness || Essential || Essential
|-
| core collection date || Essential || Essential
|-
| methodology used to calculate age || Essential || Essential
|}

===== Radiocarbon =====

{| class= "wikitable"
|-
|+Recommendation for chronologies based on radiocarbon
|-
! Question || New datasets || Legacy datasets
|-
| sample ID || Essential || Essential
|-
| type/matrix || Essential || Essential
|-
| chemical pretreatment || Recommended || Recommended
|-
| analytical method || Essential || Essential
|-
| laboratory ID || Essential || Recommended
|-
| d13C ratio || Recommended || Recommended
|-
| conventional radiocarbon age || Essential || Essential
|-
| F14C (13C and background correction applied) || Essential || Recommended
|-
| marine reservoir age || Essential || Essential
|-
| deltaR value || Essential || Essential
|-
| hard/soft water effect || Recommended || Recommended
|-
| other corrections || Recommended || Recommended
|}

===== U series =====

{| class= "wikitable"
|-
|+Recommendation for chronologies based on U-series
|-
! Question || New datasets || Legacy datasets
|-
| all isotopes ratios and concentrations measured || Essential || Essential
|-
| uncertainty for all parameters || Essential || Essential
|-
| uncertainty expressed as 2sigma || Essential || Essential
|-
| state whether uncertainty on decay constant are included in final estimates || Essential || Essential
|-
| sample identifier || Essential || Essential
|-
| reference material name || Essential || Essential
|-
| reference material descriptions || Essential || Recommended
|-
| reference material values || Essential || Essential
|-
| decay constant used || Essential || Essential
|-
| isotopes in spike || Essential || Recommended
|-
| method of spike calibration || Essential || Recommended
|-
| method of calibration for all activity or atom ratios reported (e.g. secular equilibirum or gravimetric) || Essential || Essential
|-
| activity or atom ratios for 230Th/238U (or 230Th/234U) and 234U/238U || Essential || Essential
|-
| 230Th/232Th activity or atom ratio || Essential || Essential
|-
| calibration model || Essential || Essential
|-
| date of analysis or reference age || Recommended || Recommended
|-
| concentrations of 238U, 234U, 230Th, 232Th (plus 226Ra and Ba if measured) || Essential || Essential
|-
| sample preparation || Essential || Essential
|-
| chemical separations || Essential || Recommended
|-
| sample preservation || Essential || Recommended
|-
| sample mineralogy || Recommended || Recommended
|-
| bulk composition and mineral phases (for silicates) || Essential || Recommended
|}

==== Relative chronologies ====

{| class= "wikitable"
|-
|+Recommendation for relative chronologies
|-
! Question || New datasets || Legacy datasets
|-
| original measurements || Essential || Essential
|-
| alignment target || Essential || Essential
|-
| labelling features || Essential || Recommended
|-
| method (employed software or manual) || Essential || Essential
|-
| flag for mixed chronologies || Essential || Recommended
|}

==== Software ====

{| class= "wikitable"
|-
|+Recommendation for chronology software
|-
! Question || New datasets || Legacy datasets
|-
| method (e.g., Bacon, Oxcal, Bchron, BAM...) || Essential || Essential
|-
| publication information about the software || Essential || Recommended
|-
| code || Desired || Desired
|-
| parameters || Recommended || Recommended
|-
| ensemble age models if applicable || Recommended || Recommended
|-
| ensemble statistics if applicable || Recommended || Desired
|}

===Uncertainties===

See the discussion on the uncertainties working group [[:Category:Uncertainty Working Group | page]]

==== Measured variables ====

{|class= "wikitable"
|-
|+Recommendation for reporting uncertainties on the measured variables
|-
! Question || New datasets || Legacy datasets
|-
| analytical uncertainty || Essential || Recommended
|-
| reproducibility || Recommended || Recommended
|-
| if based on reproducibility, number of repeat measurements || Essential || NA
|}

==== Models ====

{|class= "wikitable"
|-
|+Recommendation for reporting uncertainties on models
|-
! Question || New datasets || Legacy datasets
|-
| publication information about the software || Essential || Recommended
|-
| parameters || Essential || Recommended
|-
| output ensembles || Recommended || Recommended
|-
| output summary statistics (e.g., mean, media, standard deviation) || Recommended || Recommended
|}

==Road to v2.0==

A discussion forum on how to evolve this standard is available through the [http://linked.earth/forums/forum/pacts-v1-0/ LinkedEarth site]. A blog post summarizing priorities is available [http://linked.earth/paleoclimate-data-standards-a-community-pact-and-its-future/ here].

Talk:PAGES2k

2019-04-24T21:00:27Z

Jeg: added the 2013 update of the Cobb et al 2013 Palmyra record as potential addition

== Known issues with the representation of the datasets in LinkedEarth -- [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 11:35, 26 July 2017 (PDT) ==

I started a [[Known_Issues_With_LinkedEarth_Representation_of_the_PAGES2k_Dataset | page]] with some known issues to make the LiPD datasets compatible with the newest LinkedEarth Ontology. The page returns the result of the queries to identify the datasets more quickly.

== candidates for addition ==

*[https://www.researchgate.net/publication/322343777_Tracing_winter_temperatures_over_the_last_two_millennia_using_a_NE_Atlantic_coastal_record/references Asteman et al 2018]
*[http://wiki.linked.earth/Palmyra.Cobb.2013 Palmyra 2013]

Talk:PAGES2k

2018-07-30T17:18:17Z

Jeg: started list of candidates

Linked Paleo Data

2018-07-12T23:52:55Z

Jeg: /* Structuring data : the LiPD Way */

= LiPD: Linked Paleo Data =

[[File:LiPD Logo.jpg |thumb|400px|right]]

== The LiPD vision ==

Paleoclimate investigators have made a major effort over the past decade to make their data available to the broader community, largely through online archiving systems like the [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data World Data Center for Paleoclimatology] and [http://www.pangaea.de/ Pangaea]. However, there is no agreed-upon data standard for how to store and exchange such data. As the number of records in these archives has grown, making connections manually has thus become more and more challenging, hampering integrative efforts at the very time they should be flourishing. Paleoclimatologists thus need a common tongue to describe their datasets to each other and to machines.

LiPD (Linked Paleo Data) proposes such a common tongue. It is a universally-readable data container that organizes data and metadata in a uniform way, such that they may be web-searchable, and such that a variety of code functionalities may be built and apply instantly to any dataset that observes that standard.

For more details, see [http://www.clim-past-discuss.net/11/4309/2015/cpd-11-4309-2015.html this article].

== LiPD in LinkedEarth ==

LiPD is a convenient way to store and exchange paleoclimate format, and provides the backbone of the LinkedEarth edifice. LiPD is closely aligned with the [[LinkedEarth Ontology]]; changes in one are often reflected in the other (with a small lag).

= Structuring data : the LiPD Way =
== LiPD components ==

[[File:Lipd_structure.png|400px|thumb|right|structure of a lipd file. For an animated presentation see [http://prezi.com/svmit2ys9_d7/?utm_campaign=share&utm_medium=copy&rc=ex0share this prezi]]]

There are 6 possible components to a LiPD dataset. To be considered valid, a LiPD file must observe the structure to the right, and contain basic metadata for at least some of these categories.
=== Root Metadata ===
This describes metadata that applies to the whole dataset. Common examples are:
*Dataset Name
*Investigators
*Link to online dataset
*LiPD version

=== Geographic Metadata ===
Here the the site location is described following the geoJSON standard. This includes:
*Coordinates
*Sitename
*Descriptive location (e.g.,)
**Country
**State
**Province
**Ocean

=== Publication Metadata ===
Describes publications, either traditional or data publications are described following the bibJSON standard. This includes:
*Authors
*Title
*Journal
*DOI
*Year
*URL

=== Funding Metadata ===
Includes information about the research that produced the data were funded, including:
*Funding agency
*Funding grant

=== PaleoData Table ===
This includes all of the measured and inferred paleoenvironmental data - essentially all of the measurements and data from the study that were not used to infer the age. This includes:

====Measurement Tables====
*Column names, units and descriptions
*Interpretation metadata
*Calibration metadata

====Models====
*Methodology used to produce the model results
*Summary table of model output
*Ensemble tables of data produced by the model
*Distribution tables of data produced by the model

=== ChronData Table ===
This mirrors [[Linked_Paleo_Data#PaleoData_Table | PaleoData]] but only includes the data from the study that were used to infer the age of the sequence. This includes:

====Measurement Tables====
*Column names, units and descriptions

====Models====
*Methodology used to produce the model results
*Summary table of model output
*Ensemble tables of data produced by the model
*Distribution tables of data produced by the model

== LiPD implementation ==

LiPD is centered on [http://json-ld.org/ JSON-LD], a [http://www.json.org/ JSON]-based format compliant with the [https://vimeo.com/36752317 Linked Data] paradigm. JavaScript Object Notation (JSON) is an extremely lightweight and flexible way to encode information, and has become the leading format for data exchange on the Web. [http://www.ted.com/talks/tim_berners_lee_on_the_next_web Linked Data] are datasets that observe common rules to be able to be automatically linked through the World Wide Web. A LiPD file (.lpd) is in fact a zipped folder that follows the [https://en.wikipedia.org/wiki/BagIt BagIt] standard:

This includes:
*The BagIt "payload":
**One json-ld file that describes all of the metadata
**Csv tables that include data from all of the tables
*BagIt complementary information, including:
**a “bag-info.txt” file which details metadata for the bag, using colon-separated key/value pairs
**a tag manifest file which lists tag files and their associated MD5 checksums

BagIt is needed to ensure that all the bits on your computer are the same as the bits on the server.

== Working with LiPD data ==

{{See also|GeoChronR|Pyleoclim|LiPD Utilities}}

LiPD was designed so that it can capture much richer sets of (meta)data than ASCII or Excel files, and to have a fixed backbone around which scientific codes can be built.
There is a price to pay for this power: LiPD is undoubtedly more difficult to interact with than a plain text file. Although it is possible to unzip a .lpd file and navigate through the native json-ld and csv files, this is not the best way to harness the power of LiPD files.

This very wiki was designed to allow non-coders to directly access and edit LiPD files. Additionally, a growing number of utilities and software packages can read and write LiPD files, and enable users to readily take advantage of its rich structure:

===List of utilities and software that read and write LiPD===
* [[LiPD Utilities]] in:
**Matlab
**Python
**R
*[[GeoChronR]], an R package for age-modeling and associated ensemble-based workflows (spectral analysis, PCA, correlations, etc.)
*[https://www.cs.colorado.edu/~lizb/cscience.html CSciBox], see [http://linked.earth/featured-partnership-cscience-linkedearth/ this post by Liz Bradley on how LiPD changed how they do science]
*[[Pyleoclim]], a Python package to analyze and visualize paleo data.

== Getting your data into LiPD ==
{{See also|Creating a LiPD file|label 1= creating a LiPD file}}

Once data are in LiPD, and the LiPD file is [http://lipd.net/validator valid], everything is [https://www.youtube.com/watch?v=StTqXEQ2l-Y awesome].

How do you get paleo data into LipD, you ask? This is now very easy thanks to the [http://lipd.net/playground LiPD playground], which enabled basic quality checks along the way. Soon LiPD creation will leverage the [[LinkedEarth_Ontology]] and NOAA's controlled vocabulary. Stay tuned for more updates.

PAGES2k

2017-10-24T18:00:27Z

Jeg: changed logo to 2017 version

[[Category:Compilation (L)]]{{#set:
Author (L)=J._Emile-Geay|
Author (L)=Nick_McKay|
Author (L)=Darrell|
Author (L)=Lucien_von_Gunten|
Author (L)=Kevin_Anchukaitis|
Author (L)=PAGES2k_consortium|
CompilationCitation (L)=PAGES2k Consortium, A global multiproxy database for temperature reconstructions of the Common Era, Scientific Data, in press|
CompilationName (L)=PAGES2k|
CompilationVersion (L)=2.0.0|
FundedBy (L)=National_Science_Foundation.ICER-1541029|
HasLink (L)=http://www.ncdc.noaa.gov/paleo-search/study/21171|
HasLink (L)=https://figshare.com/s/d327a0367bb908a4c4f2|
ModeledBy (L)=PAGES2k.Model1|
PublishedIn (L)=Publication.10.1038/sdata.2017.88}}

__NOCACHE__
[[File:PAGES2k-network-logo.jpg|thumb|right|alt=PAGES2k logo]]

== Description ==
Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. The '''PAGES2k Phase 2 collection''' is a community-sourced compilation of temperature-sensitive proxy records associated with the [http://www.pastglobalchanges.org/ini/wg/2k-network/intro PAGES2k initiative]. The (soon to be published) database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial vs marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era.

== Revisions and updates ==
Revisions happen continually on the wiki, and are tracked by the system. When changes are substantive enough that new releases are warranted, they will be explained here by a change log.

The PAGES2k versioning scheme is as follows: the version number for a data compilation is of the form C1.C2.C3, where C1 is a counter associated with a publication of the dataset, C2 is a counter updated every time a record is added or removed, and C3 is a counter updated every time a modification is made to the data or metadata in an individual record.

== How to cite ==
This section should encourage users to include multiple citations for each of the records: (a) the original publication where the data are described; (b) the data citation to the raw dataset; (c) the data citation to any modified versions of the dataset. In addition, (d) if users rely on metadata or other features of the compilation, they should cite the PAGES2k data product. This section should explain the principles of tracking and attributing data and provide a link to that informs users about data citations.

== Downloads ==
The data are available on this wiki as LiPD files.
Additionally, the data will be made available on [https://doi.org/10.6084/m9.figshare.c.3285353 FigShare] and at the [http://www.ncdc.noaa.gov/paleo-search/study/21171 National Center for Environmental Information/World Data Service for Paleoclimatology]

== Datasets in the PAGES2k database ==



{{ #ask:
[[Category:Dataset_(L)]]
[[IncludesPaleoData_(L).FoundInMeasurementTable_(L).IncludesVariable_(L).InCompilation:: PAGES2k_v1.12.0]]
| ?ArchiveType=ArchiveType
| format=broadtable
| limit=20
}}{{#subobject:_QUERY828b4b9c541e880cdace32132f7896ac}}

File:PAGES2k-network-logo.jpg

2017-10-24T17:59:51Z

Jeg:

Paleoclimate Data Standards

2017-10-24T17:42:56Z

Jeg: /* Voting */ included link to Google Survey

= Background =
== What is a standard? ==
[http://www.earthcube.org/document/2015/ecstandardsrecs EarthCube defines] a standard as follows:

a public specification documenting some practice or technology that is adopted and used by a community. [..] There is a continuum starting with any documented practice in some community. If lots of people use a particular documented practice it could be adopted as a best practice. If almost everyone uses some documented practice, then it is a de facto standard.

Notice the emphasis on community and on practice. If only person uses a technical specification, it's not a standard. If it's voted on but not applied in practice, it's worthless as well. Thus, the objective of this EarthCube activity is to propose a standard with broad community appeal and adoption.

== Why do we need standards? ==
Modern life would simply be unlivable without standards. Imagine having to use a separate browser for each web page your visit, or a separate power-transmission system for every appliance you use! You only have to travel to a country that uses a different electric plug than the one your computer and phone employ to appreciate what a nightmare that would be. In science, the ultimate objective of a standard is to make data understandable by others (including machines), and the derived analyses reproducible. Thus, a key objective of LinkedEarth is to promote the development of a community standard for paleoclimate data. Indeed, despite some ad-hoc gatherings among communities of interest over many years, until recently there had never been a concerted effort to produce a standard applicable to all paleoclimate observations. Given the increased importance of synthesis work (e.g. PAGES2k, Shakun et al 2012, Marcott et al 2013, MARGO, others), it is increasingly important that a common solution be found.

= Prior Work =
== Pre-2016 ==
Here is a non-exhaustive list of past discussions that we are aware of:

* [[media: Reporting_Standards_for_Paleoceanographic_PMIP3_Dec2013.docx | PMIP3 Workshop in Corvallis]] (December 2013)
* [http://www.clivar.org/sites/default/files/documents/TriesteReport_nov5.pdf report for the workshop "REPRESENTING AND REDUCING UNCERTAINTIES IN HIGH-RESOLUTION PROXY CLIMATE DATA"] (Trieste, Italy, June 2008)

We welcome any summaries of prior discussions on data standards you may have had at meetings, workshops. To do so, either link to a document that you have uploaded on the wiki or create a new page and list it here.

== LiPD ==
The [[Linked_Paleo_Data|LiPD]] format embodies one part of this solution: it offers a container that can wrap tightly around a wide varieties of paleoclimate [[:Category:Dataset (L)|datasets]], providing a vessel for paleoclimate content. Other formats, of course, would be acceptable; however, there is no viable alternative currently in existence, which is why [[Nicholas_McKay | Nick]] and [[J._Emile-Geay | Julien]] had to go through the trouble of inventing such a format. Another reason to adopt it is that '''there is a growing code ecosystem being developed around LiPD''' in Matlab, R and Python: the [https://github.com/nickmckay/LiPD-utilities LiPD utilities] that allow cross-walk between all kinds of commonly-used formats, [http://nickmckay.github.io/GeoChronR/ GeoChronR] for the analysis of time-uncertain paleo data, and [https://github.com/LinkedEarth/Pyleoclim_util Pyleoclim] to visualize and analyze the data.
Why not just stick with LiPD and call it a day, you ask? Well, LiPD's infinite flexibility is a double-edge sword: it can accommodate all manner of information, but that information may or may not align with community best practices. It is thus '''necessary for the community to decide on such practices'''. In other words, if LiPD provides a field-tested answer to the question: ''how should paleoclimate data be stored?'', it says nothing about '''''what''''' should be stored: that decision is up to the community.

== First workshop on paleoclimate data standards ==
The [[PDS_workshop_2016 | 2016 workshop on paleoclimate data standards]] (PDS workshop, for short) served as a stepping stone to initiate a broader process of community engagement and feedback elicitation, with the goal of generating such a community-vetted standard. The workshop identified a need to '''delineate a set of essential, recommended and desired properties for each dataset'''.
By default, any and all information is desired. A subset of that should be recommended to ensure optimal re-use. Yet a smaller subset of that is '''essential''' in the sense that a paleoclimate data set should not be acceptable without this information (for more details, see the [[PDS_workshop_2016 | PDS workshop page]]). Four additional themes emerged:

=== Cross-Archive Standards ===
Some essential data/metadata are shared among all conceivable archive types:

* '''A table with at least two columns''', one representing time, the other a climate indicator of some sort
* '''Geolocation''': coordinates, polygons, or, in cases where coordinates or polygons cannot be given, general location info
* '''Source''': PI, contributor, or database (first author of publication if published, or some other person who can speak for the dataset if not published/if the first author is no longer in science/etc)
* '''Names''' and '''Units''' of the variables in the dataset

=== Archive-specific standards ===
What is needed to intelligently re-use a marine-annually resolved record could be quite different than what is needed to intelligently re-use an ice core record, for instance. Therefore, these these levels are archive-specific.

=== Legacy vs Modern datasets ===
The group also recognized that standards need to be more stringent for modern datasets than for legacy datasets, for which some (meta)data are sometimes impossible to procure (think: raw radiocarbon dates from a PI now deceased). Thus, for every archive and across archives, there needs to be different set of standards for both kinds.
What constitutes "legacy" data is also open to interpretation, and requires a formal definition (and a vote).

=== Audience and Purpose ===
Finally, it was recognized that all of the above considerations are a function of who is using the data, and for what purpose. As such, it is useful to consider a few science drivers.

= Science Drivers =
One possible way to elaborate a standard is to ask oneself: "What pieces of metadata would I require to reproduce this particular dataset and therefore which one should I provide for my own datasets?" Some of these metadata will be standard across all archives (i.e., geographic coordinates, publication information). Some will be specific to each archive or observation type. See [[:Category:Marine_Sediment_Working_Group | here]] for an example of such discussions on foraminiferal Mg/Ca.

== Querying the datasets ==

Another way to think about the essential/recommended/optional metadata is to think about the kind of queries one would want to enable for their research. For instance, a recent study on [http://linked.earth/wp-content/uploads/2016/01/Khider_AGUFall16.pdf Testing the Millennial-Scale Solar-Climate Connection in the Indo-Pacific Warm Pool] required the following queries and associated metadata:

{| class="wikitable"
|-
! Query || Required Metadata
|-
| SST-sensitive proxies (i.e. Mg/Ca, Uk37 and TEX86) || Needed a property describing the proxy observations as well as a standard to express the concept of Mg/Ca, TEX86 and UK37. This need gave rise to [[:Property:ProxyObservationType_(L)]] and terms in the ontology [[:Category:ProxyObservation_(L)]] to describe these concepts.
|-
| Holocene data (0-10ka) spanning at least 5kyr || Needed a property describing the concept of [[Age]], giving rise to [[:Property:InferredVariableType (L)]]. An ontology for [[:Category:InferredVariable_(L)]] is in progress. It also became obvious that we needed to standardize the way to represent time and the units of time. Furthermore, since the wiki doesn't read the content of the .csv file, some metadata about the values stored in the .csv file were also needed. We therefore created the following properties: [[:Property:HasMinValue (L)]], [[:Property:HasMaxValue (L)]], [[:Property:HasMeanValue (L)]].
|-
| In the IndoPacific Warm Pool || We needed to query the dataset by latitude/longitude.
|}

Other types of basic query include searching for a particular publication, using either the DOI, title, journal, authors, and searching by [[:Category:ProxyArchive_ (L) | archiveType]]. The latter is currently used to obtain the maps under each archive category (for example, [[:Category:MarineSediment | marine sediments]]). Enter the queries you'd like to perform, and the metadata required to perform them.

== Analyzing the datasets ==

Finally, this problem can be approached from a data analysis point-of-view. "Given my interest, what are the required information I would need to perform my analysis?"

For instance, if all is known about a dataset are the geographical coordinates from which the archive was taken, then the only possible analysis is to create a location map of said archive (with or without its nearest neighbor contained in the database). On the other hand, if an age and paleo variable are contained within the PaleoDataTable, the resulting time series can be used for correlation analysis and spectral analysis. However, without the raw age data, it would be impossible to recalibrate the record using updated techniques, limiting its usefulness. To ask the most questions of our datasets, and do the best science, we need them to be as complete as possible.

For the Holocene study, the datasets had to contain the raw radiocarbon measurements for use with [https://cran.r-project.org/web/packages/Bchron/vignettes/Bchron.html Bchron]. [http://linked.earth/doing-science-with-linkedearth/ this blog post] describes how richer and standardized metadata supported the study. This [https://github.com/khider/Holocene-Millennial-Scale-Variability/blob/master/AGU%20Fall%202016/Holocene_MillennialScaleVar.md Jupyter Notebook] integrates code, data and text to walk you through the story. None of this would have been possible without [[Linked_Paleo_Data|LiPD]].

= Process for achieving a paleoclimate data standard=
== Working Groups ==
Attendees of the [[PDS workshop 2016]] proposed that archive-centric [[:Category:Working_Group | working groups]] (WGs; self-assembled coalitions of knowledgeable experts) would be best positioned to elaborate and discuss the components of a data standard for their specific sub-field of paleoclimatology. It is also critical to ensure interoperability between standards to enable longitudinal (multiproxy) investigations.
[[:Category:Working_Group | Working groups]] have been formed and are now being consulted to generate the backbone of a standard, which has been presented to the community at the [http://www.pages-osm.org PAGES OSM meeting] in Zaragoza (May 9-13, 2017).

Current Working Groups:
<DynamicPageList>
category = Working Group
shownamespace = false
</DynamicPageList>

== International Partners ==
This process contributes to the [http://pastglobalchanges.org/ini/int-act/data-stewardship data stewardship initiative] of our [http://www.pastglobalchanges.org/about/general-overview PAGES/Future Earth] partners. Therefore, we are working together with PAGES to reach out to the broadest cross-section of paleoscientists and invite them to contribute to the process. The end goal is a standard to be precisely documented and adopted by LinkedEarth and PAGES. The standard will be implemented in all LinkedEarth activities and proposed for adoption by [http://earthcube.org/ EarthCube], the [https://rd-alliance.org/ Research Data Alliance], the [http://www.esipfed.org/ Federation of Earth Science Information Partners], [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data NOAA WDS-Paleo] and [https://www.pangaea.de/ Pangaea].

== Voting ==
=== Wiki-based voting ===
The first phase of input on data standards (up to October 2017), open only to LinkedEarth members, has leveraged the wiki's polling ability. The results of such polls are summarized in [[PollingStats|Advanced Statistics]].
=== Google Survey ===
The second phase of input, open to all scientists who want to be associated with the Data Standards publication, is available [https://t.co/SUhcYojPJq here] as a Google Survey. It is active until November 10, 2017.

= Standard Publication =
Once the community has spoken on these matters, the decisions will be summarized in a publication.

A formal standard is a specification of some practice that is adopted by a recognized standards body. The set of formal standards and set of de facto standards intersect, but are not the same; some formal standards are not very widely used. Nonetheless, because of the community participation and rigor required to formalize the standard we recognize that they merit careful evaluation. [http://www.earthcube.org/document/2015/ecstandardsrecs]

In the internet age, a standard can be a web-based document that details all the specifications pertaining to a technical matter. To encourage community participation and promote transparency, the LinkedEarth team will lead a '''crowd-sourced peer-reviewed publication''' detailing this standard.

==Platform==
The writing process will take place in the collaborative platform [https://www.authorea.com Authorea] and synthesize the decisions taken, and the pertinent discussions that led to such decisions.

==Authorship==
Pursuant to PAGES policies, authorship will be extremely inclusive and acknowledge all scientific input into the process. Anyone contributing to the discussion on developing standards for paleoclimatology (either during the [[PDS workshop 2016]], on the wiki, or via teleconferences an in-person exchanges) will be invited to the author list.

Authorship will be consortium-based (provisional name: "Working Group on Paleo Data Standards")

MD982176.Stott.2004

2017-09-20T21:45:20Z

Jeg: Added PropertyValue: Keywords = Earth

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[[File:Plot timeseries MD982176.Stott.2004 Sea Surface Temperature (deg C).png | 700px]]

MD982176.Stott.2004

2017-09-20T21:45:09Z

Jeg: Set PropertyValue: Keywords = paleoclimate

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[[File:Plot timeseries MD982176.Stott.2004 Sea Surface Temperature (deg C).png | 700px]]

MD982176.Stott.2004

2017-09-20T21:44:58Z

Jeg: Added PropertyValue: Keywords = paleoenvironment

[[Category:Dataset_(L)]]{{#set:
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LiPDVersion=1.2|
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[[File:Plot timeseries MD982176.Stott.2004 Sea Surface Temperature (deg C).png | 700px]]

MD982176.Stott.2004

2017-09-20T21:44:43Z

Jeg: Added PropertyValue: Keywords = paleoceanography

[[Category:Dataset_(L)]]{{#set:
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[[File:Plot timeseries MD982176.Stott.2004 Sea Surface Temperature (deg C).png | 700px]]

Property:Keywords

2017-09-20T21:44:09Z

Jeg: allow for multiple values

Property type: [[has type::Text]]
[[has multiple values::true]]

MD982176.Stott.2004

2017-09-20T21:42:34Z

Jeg: Added PropertyValue: Keywords = climate

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[[File:Plot timeseries MD982176.Stott.2004 Sea Surface Temperature (deg C).png | 700px]]

Property:Keywords

2017-09-20T21:41:31Z

Jeg: Changed Keyword property range from "Page" to "Text"

Property type: [[has type::Text]]

MD982176.Stott.2004

2017-09-20T21:38:44Z

Jeg: Set PropertyValue: Description (L) = This dataset describes ocean temperature variability west of Papua (Arafura Sea) over the past 14,000 years

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[[File:Plot timeseries MD982176.Stott.2004 Sea Surface Temperature (deg C).png | 700px]]

Property:Keywords

2017-09-18T17:13:42Z

Jeg: Creating new Property

Property type: [[has type::Page]]

MD982181.Khider.2014

2017-09-18T17:13:42Z

Jeg: Added PropertyValue: Keywords = paleoclimate, climate, environment, Earth

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DatasetLicense (L)=https://creativecommons.org/licenses/by/3.0/us/|
DatasetVersion (L)=0.0.0|
Description (L)=This dataset describes ocean temperature variability south of Mindanao, Philippines over the past 10,000 years.|
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[[File:MD982181.Khider.2014.SummaryPlot.SST.png | 700px]]

MD982181.Khider.2014

2017-09-15T23:56:15Z

Jeg: Added PropertyValue: DatasetLicense (L) = https://creativecommons.org/licenses/by/3.0/us/

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DatasetLicense (L)=https://creativecommons.org/licenses/by/3.0/us/|
DatasetVersion (L)=0.0.0|
Description (L)=This dataset describes ocean temperature variability south of Mindanao, Philippines over the past 10,000 years.|
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[[File:MD982181.Khider.2014.SummaryPlot.SST.png | 700px]]

Category:Chronologies Working Group

2017-08-19T00:00:32Z

Jeg: ref to Cox & Richard added

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix _ yearlyIncrement _ suffix'''

* Possible instances of '''yearlyIncrement''' are : ''year, years, annum, annums'', etc
* Possible instances of '''prefix''' are: ''none, kilo, mega, giga''; this conveys information about the multiplicative factor that needs to be applied to the increments.
* Possible instances of '''suffix''' are: ''none, BP, CE, AD''. the suffix conveys information about the direction of time flow, and the reference point (with some ambiguity that needs resolving).

- For ''years CE'', the prefix is none, the yearlyIncrement is years, the suffix is CE. Thus time flows forward from the origin of the Common Era, which is sometimes placed at year 0 (astronomical calendar, or [https://www.iso.org/iso-8601-date-and-time-format.html ISO8601]), sometimes at year 1. A system for disambiguation is needed (perhaps by attaching an ISO standard).

- For ''kyr BP'' the suffix conveys that time flows in reverse from the present day, again defined with some ambiguity as 1950 CE or 2000 CE (see Age poll). The prefix is kilo, indicating that a factor of 1000 needs to be applied.

- For "Ga", the prefix is giga, indicating a billion factor. The increment is "annum", and the suffix is none, indicating implicitly something like BP (where the 1950 or 2000 reference point is immaterial given the time spans involved.

Thus, the direction of time flow (forward or backward) can always been inferred from context; however, the diversity of spelling and abbreviations makes it difficult for machines to guess this, and thus a more disciplined representation would be helpful. For all representations, one might consider an internal representation like `kilo_years_BP`, and an external representation for display purposes like `kyr BP`.

Lastly, we note that the excellent ontology of geologic time by Cox & Richard<ref>Cox, S. J. D., and S. M. Richard (2015), A geologic timescale ontology and service, Earth Science Informatics, 8(1), 5–19, doi:10.1007/s12145-014-0170-6.</ref>, which deals with >1Ma time scales, does not encompass such distinctions, and thus a new representation is needed.

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T23:57:01Z

Jeg:

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix _ yearlyIncrement _ suffix'''

* Possible instances of '''yearlyIncrement''' are : ''year, years, annum, annums'', etc
* Possible instances of '''prefix''' are: ''none, kilo, mega, giga''; this conveys information about the multiplicative factor that needs to be applied to the increments.
* Possible instances of '''suffix''' are: ''none, BP, CE, AD''. the suffix conveys information about the direction of time flow, and the reference point (with some ambiguity that needs resolving).

- For ''years CE'', the prefix is none, the yearlyIncrement is years, the suffix is CE. Thus time flows forward from the origin of the Common Era, which is sometimes placed at year 0 (astronomical calendar, or [https://www.iso.org/iso-8601-date-and-time-format.html ISO8601]), sometimes at year 1. A system for disambiguation is needed (perhaps by attaching an ISO standard).

- For ''kyr BP'' the suffix conveys that time flows in reverse from the present day, again defined with some ambiguity as 1950 CE or 2000 CE (see Age poll). The prefix is kilo, indicating that a factor of 1000 needs to be applied.

- For "Ga", the prefix is giga, indicating a billion factor. The increment is "annum", and the suffix is none, indicating implicitly something like BP (where the 1950 or 2000 reference point is immaterial given the time spans involved.

Thus, the direction of time flow (forward or backward) can always been inferred from context; however, the diversity of spelling and abbreviations makes it difficult for machines to guess this, and thus a more disciplined representation would be helpful. For all representations, one might consider an internal representation like `kilo_years_BP`, and an external representation for display purposes like `kyr BP`.

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T23:56:32Z

Jeg:

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix _ yearlyIncrement _ suffix'''

* Possible instances of '''yearlyIncrement''' are : ''year, years, annum, annums'', etc
* Possible instances of prefix are: ''none, kilo, mega, giga''; this conveys information about the multiplicative factor that needs to be applied to the increments.
* Possible instances of suffix are: ''none, BP, CE, AD''. the suffix conveys information about the direction of time flow, and the reference point (with some ambiguity that needs resolving).

- For ''years CE'', the prefix is none, the yearlyIncrement is years, the suffix is CE. Thus time flows forward from the origin of the Common Era, which is sometimes placed at year 0 (astronomical calendar, or [https://www.iso.org/iso-8601-date-and-time-format.html ISO8601]), sometimes at year 1. A system for disambiguation is needed (perhaps by attaching an ISO standard).

- For ''kyr BP'' the suffix conveys that time flows in reverse from the present day, again defined with some ambiguity as 1950 CE or 2000 CE (see Age poll). The prefix is kilo, indicating that a factor of 1000 needs to be applied.

- For "Ga", the prefix is giga, indicating a billion factor. The increment is "annum", and the suffix is none, indicating implicitly something like BP (where the 1950 or 2000 reference point is immaterial given the time spans involved.

Thus, the direction of time flow (forward or backward) can always been inferred from context; however, the diversity of spelling and abbreviations makes it difficult for machines to guess this, and thus a more disciplined representation would be helpful. For all representations, one might consider an internal representation like `kilo_years_BP`, and an external representation for display purposes like `kyr BP`.

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T23:56:00Z

Jeg:

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix _ yearlyIncrement _ suffix'''

* Possible instances of '''yearlyIncrement''' are : ''year, years, annum, annums'', etc
* Possible instances of prefix are: ''none, kilo, mega, giga''; this conveys information about the multiplicative factor that needs to be applied to the increments.
* Possible instances of suffix are: ''none, BP, CE, AD''. the suffix conveys information about the direction of time flow, and the reference point (with some ambiguity that needs resolving).

- For ''years CE'', the prefix is none, the yearlyIncrement is years, the suffix is CE. Thus time flows forward from the origin of the Common Era, which is sometimes placed at year 0 (astronomical calendar, or [https://www.iso.org/iso-8601-date-and-time-format.html ISO8601]), sometimes at year 1. A system for disambiguation is needed (perhaps by attaching an ISO standard).

- For ''kyr BP'' the suffix conveys that time flows in reverse from the present day, again defined with some ambiguity as 1950 CE or 2000 CE (see Age poll). The prefix is kilo, indicating that a factor of 1000 needs to be applied.

- For "Ga", the prefix is giga, indicating a billion factor. The increment is "annum", and the suffix is none, indicating implicitly something like BP (where the 1950 or 2000 reference point is immaterial given the time spans involved.

Thus, the direction of time flow (forward or backward) can always been inferred from context; however, the diversity of spelling and abbreviations makes it difficult for machines to guess this, and thus a more disciplined representation would be helpful. For all representations, one might consider an internal representation like `kilo_years_BP`, and an external representation for display purposes like `kyr BP`.

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T23:52:27Z

Jeg:

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix _ yearlyIncrement _ suffix'''

* Possible instances of '''yearlyIncrement''' are : ''year, years, annum, annums'', etc
* Possible instances of prefix are: ''none, kilo, mega, giga''; this conveys information about the multiplicative factor that needs to be applied to the increments.
* Possible instances of suffix are: ''none, BP, CE, AD''. the suffix conveys information about the direction of time flow, and the reference point (with some ambiguity that needs resolving).

For ''years CE'', the prefix is none, the yearlyIncrement is years, the suffix is CE. Thus time flows forward from the origin of the Common Era, which is sometimes placed at year 0 (astronomical calendar, or [https://www.iso.org/iso-8601-date-and-time-format.html ISO8601]), sometimes at year 1. A system for disambiguation is needed (perhaps by attaching an ISO standard).

For ''kyr BP'' the suffix conveys that time flows in reverse from the present day, again defined with some ambiguity as 1950 CE or 2000 CE (see Age poll). The prefix is kilo, indicating that a factor of 1000 needs to be applied.

For "Ga", the prefix is giga, indicating a billion factor. The increment is "annum", and the suffix is none, indicating implicitly something like BP (where the 1950 or 2000 reference point is immaterial given the time spans involved.

Thus, the direction of time flow (forward or backward) and always been inferred from context; this is

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T23:44:00Z

Jeg: new section on time representation

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix _ yearlyIncrement _ suffix'''

# Possible instances of yearlyIncrement are : ''year, years, annum, annums'', etc
# Possible instances of prefix are: ''none, kilo, mega, giga''
# Possible instances of suffix are: ''none, BP, CE, AD''

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T23:40:54Z

Jeg:

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

=== Unifying representations ===
The aforementioned concepts are in fact the same: time.
One way to unify its representation is to recognize that all known applications use something of the form:

'''prefix ___ increment ___ suffix'''

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

Category:Chronologies Working Group

2017-08-18T17:05:53Z

Jeg: fixed typos

[[Category:Working Group]]
[[File:Chronology_pic.png|thumb|right|alt=An imaginary chronology based on U/Th dates, generated via Bchron|Credit: Julien Emile-Geay (Own work)]]

== Overview ==
In the Linked Earth context, a [[:Category:Working_Group|working group]] (WG) is a self-organized coalition of knowledgeable experts, whose activities are governed [[:Category:Working_Group|herewith]]. This page is dedicated to the discussion of data and metadata standards for '''chronologies''', and aims to formulate a set of recommendations for such a standard.

This WG needs to work closely with other WGs, as constraints will vary by archive. Nevertheless, some aspects are common enough that it is worth pursuing some general recommendations, and devise ''ad hoc'' adjustments for individual archives if need be. It is recommended that every WG coordinator join this WG to keep track of discussions.

=== Members ===

The chronologies Working Group has one coordinator, [[Christof_Pearce | Christof Pearce (Stockholm University)]]

__MEMBERS__

== Specific tasks ==

We recommend that discussions focus on the following techniques, and explore potential commonalities.

[[File:MetadataDefinitions.png | thumb | right | 400px | Definition of essential, recommended, and desired in regards to paleoclimate data standards]]

For each chronology type, we recommend:
* structuring discussions around what scientific questions one would want to ask of the data
* listing essential, recommended, and desired information for:
** the age models themselves
** the chronological measurements (ChronData tables, in LiDP/LinkedEarth parlance)
** their uncertainties, and what those numbers correspond to (e.g. 1-sigma or 2-sigma?)
* provide an '''ideal chronology table''', so the community knows what to report and how to report it.
* provide separate recommendations for new and legacy datasets

While it is recognized that most real-word chronologies are of mixed types (e.g. a Holocene lake sediment chronology may blend radiocarbon dates, {{SimpleNuclide2|Lead|210}} dates, and volcanic ash markers), it is critical to first define guidelines for how to report ''pure'' chronologies. Once the foundations are sound, they will be easier to compose together.

== Nomenclature ==

In paleoclimatology, scientists tend to reference the time axis either starting from the present (present often being taken as 1950) and counting positively back in time. In the current [[Linked_Paleo_Data | LiPD]] model, this concept is referred to as 'age'. On the other hand, some scientists, especially focusing on the last 2,000 years, use the Gregorian Calendar. In LiPD, this concept is referred to as 'year'.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Chronology AgevsYear.png | 400px |right | thumb | Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
Should we keep these two separate concepts?
Yes
No
</poll>

If yes, is the current nomenclature adopted by LiPD correct?

=== Age ===

[[File:TwitterPoll Chronology AgeReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report age?
Using BP, the present being defined as 1950
Using BP, the present being defined as the latest year in a record
Using BP, the present being defined as 2000
Something else (Comment below)
</poll>

=== Year ===

[[File:TwitterPoll Chronology YearReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 15th and 22nd 2017]]

<poll>
How should we report year?
Using AD (anno Domini)
Using CE (Common Era)
</poll>

== Recommendations from the literature ==

The recommendations below are from Govin et al. 2015 <ref name = govin2015> Govin. A., E. Capron, P.C. Tzedakis, S. Verheyden, B. Ghaleb, C. Hillaire-Marcel, G. St-Onge, J.S. Stoner, F. Bassinot, L. Bazin, T. Blunier, N. Combourieu-Nebout, A. El Ouahabi, D. Genty, R. Gersonde, P. Jimenez-Amat, A. Landais, B. Martrat, V. Masson-Delmotte, F. Parrain, M.-S. Seidenkrantz, D. Veres, C. Waelbroeck, R. Zahn, 2015. Sequence of events from the onset to the demise of the Last Interglacial: Evaluating strengths and limitations of chronologies used in climatic archives. Quaternary Science Reviews, 129, 1-36, doi:10.1016/j.quadcirev.2015.09.018.</ref>.

<blockquote> "Future climate-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations."</blockquote>

=== Absolute dating of aragonitic corals ===

Dating fossil corals often requires the use of U-series age.

==== Age calculation and its intrinsic uncertainties ====

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

<blockquote> "In recent years, most ages have been obtained through high precision TIMS or MC-ICP-MS measurements are are generally given with a ±2σ. Earlier, they were mostly obtained through alpha particle counting and generally cited with a ±1σ uncertainty. <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral USeries UncertaintyReporting.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series measurements in coral archive, should the uncertainty be reported as
±2σ
±1σ
something else (comment below).
</poll>

<blockquote> "Some vagueness persists with respect to the way quoted uncertainties include or not all potential sources of analytical errors (internal vs external precision), which makes direct comparison of databases somewhat hazardous. <ref name= govin2015 />" </blockquote>

<blockquote> "Moreover, radiometric age equations include decay constants of all concerned isotopes, which are known with some uncertainty. The comparison of such U-series ages to any other time scale, such as glaciological ages, astronomically-tunes ages and other radiometric ages, requires the U-series decay constant uncertainties to be carried into the final age error calculation <ref name= govin2015 />" </blockquote>

[[File:TwitterPoll Coral Useries DecayConstant New.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for new datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Coral USeries DecayConstant Legacy.png | 400px | thumb | right | Results of the poll placed on Twitter between July 5th and 12th 2017]]

<poll>
For U-series uncertainty in coral archive, should the uncertainty in the U-series decay constant for legacy datasets be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Comment from [[User:Kcobb]] made on [https://twitter.com/coralsncaves/status/882698713004683264 Twitter] on July 5th 2017: <blockquote> "Should be propagated through full uncertainty analysis in published dating table. But if not there, it's easy to figure out by pub date." </blockquote>

=== Dating of speleothems ===

==== Absolute dating and stratigraphic markers ====

Speleothems can be absolutely dated over the last 600ka with the U-Th methodology <ref> Helmstrom, J., 2006. U-Th dating of speleothems with high initial 230Th using stratigraphical constraint Quaternary Geochronology, 1, 289-295. </ref>, with a dating uncertainty better than 0.5% <ref> Dorale, J., Edwards, R.L., Alexander Jr., E.C., Shen, C.-C., Richards, D., Cheng, H., 2004. Uranium-series dating of speleothems: current techniques, limits, & applications. In: Sasowsky, I., Mylroie, J. (Eds), Studies of Cave Sediments, Springer, US, pp. 1777-197. http://dx.doi.org/10.1007/978-1-4419-9118-8_10. </ref> <ref> Li, H.-C., Ku, T.-L., You, C.-F., Cheng, H., Edwards, R.L., Ma, Z.-B., Tsai, W.-s, Li, M.-D., 2005. 87Sr/86Sr and Sr/Ca in speleothems for paleoclimate reconstruction in Central China between 70 and 280kyr ago. Geochimica and Cosmochimica Acta, 69, 3933-3947. http://dx.doi.org/10.1016/j.gca.2005.01.009. </ref> <ref> Cheng, H., Edwards, R.L., Broecker, W.S., Denton, G.H., Kong, X., Wang, Y., Zhang, R., Wang, X., 2009. Ice age terminations. Science 326, 248-252. http://dx.doi.org/ 10.1126/science.1177840. </ref>.

Recommendation from Govin et al. (2015) <ref name = govin2015 />

<blockquote> "Ideally, new [spleothem] records should present growth rates as high as possible and numerous U-Th dating points in order to (1) reduce dating uncertainty, (2) enhance the robustness of radiometric chronologies on centennial to millennial time scales, (3) maximize constraints on the 'accordion effect' induced by growth rate changes and (4) optimize the assessment of the synchronicity between records. <ref name = govin2015 />"</blockquote>

=== Chronologies in marine sediments ===

{| class="wikitable"
|-
|+Summary of methods used to derive chronologies in marine sediments. Adapted from Govin et al. (2015) <ref name = govin2015 />
|-
! Method || Hypotheses || Age Uncertainties || Strengths || Limitations/difficulties || Recommendation
|-
| Radiocarbon || Reservoir age correction is known and not changing over time|| See [[#Radiocarbon]] || Absolute chronologies || Reservoir Age correction ||
|-
| Synchronization of tephra horizons || Correct identification of the same tephra in different archives || rowspan = "2"|
*Absolute dating error (if available)
*Synchronization error
||
* Accurate synchronisation
* Several tephra horizons identified during the same interval
* Absolute dating control sometimes possible
||
* Taphonomic issues (reworking, dissemination, dispersion of shards)
* Unequivocal identification of source volcano and eruptive event via diagnostic fingerprinting
||
High potential of synchronization
|-
| Synchronization of geomagnetic excursions and of relative paleointensity records || Global signal || Potential to synchronize paleointensity to cosmogenic isotopic records from ice cores ||
* Large dating uncertainty of geomagnetic excursions
* Uncertainties associated with the magnetization acquisition process
|| Method suitable for local to global synchronization when sediments pass criteria of paleomagnetic reliability
|-
| Benthic foraminifera δ18O alignment || In-phase benthic δ18O variations || rowspan = "3"|
* Alignment error (e.g. resolution, matching)
* Uncertainty related to the hypothesis (e.g. possibility of diachronous high-latitude temperature changes)
* Dating uncertainty of the reference
|| Common tracer: many available records || Diachronous deep-water temperature and δ18O changes across water-masses || Method suitable between sites located within the same water mass
|-
| SST alignment to ice cores || In-phase high-latitude sea surface and air temperature changes || High-resolution ice core records for the last 800 ka ||
* Restricted to high latitudes
* Precise geographical extension of synchronous temperature changes
* Sensitive to uncertainties in SST reconstruction methods (e.g., seasonality, living depth, transport)
|| Method suitable for North Atlantic and Southern Ocean sites
|-
| Marine alignment to speleothems || In-phase regional changes in marine (e.g., SST, salinity, pollen) and continental (e.g., rainfall amount) tracers ||
* High dating accuracy
* Very high-resolution speleothem records
||
* Mostly applicable in tropical and mid-latitude regions (where speleothem records are available)
* Speleothem records sometimes discontinuous
* Climatic drivers of speleothem tracers (moisture availability?)
|| Method suitable for sites (mostly from tropical and mid-latitude regions) located close to well-dated speleothems with well-understood tracers
|}

== Tie-point chronologies ==

=== Radiocarbon ===
The following came from P. Reimer by way of T. Guilderson.

Key references: Stuiver & Polach [1977] <ref name=SP77>Minze Stuiver and H. A. Polach, 1977. Discussion: Reporting of 14C Data. Radiocarbon 19, 3, 355-363. </ref> and Reimer et al., [2004] <ref>Paula J. Reimer, T. A. Brown, and R. W. Reimer, 2004. Discussion: Reporting and calibration of post-bomb 14C Data. Radiocarbon, 46, 3, 1299-1304.</ref>

==== metadata ====

{| class="wikitable"
|-
|+Table 1: Essential/Recommended/Desired metadata for Radiocarbon measurements
|-
! Metadata || Essential (E)/Recommended(R)/Desired(D) || Reason || Added by (optional)
|-
| Sample ID|| E || Allows to provide a unique identifier to the sample || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Type/Matrix || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|-
| Location (lat/lon/alt or sample depth) || E || ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:17, 15 March 2017 (PDT) on behalf of T. Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll_Radiocarbon_SampleID.png|thumb|500px|Results of the poll ran on Twitter from March 23rd 2017 to March 30th 2017]]

<poll>
For radiocarbon measurements, should the sample ID be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the type/matrix should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

Polls on whether [[:Category:Location (L)| location]] information should be essential, recommended or desired metadata for new dataset can be found [[Cross_Archive_Metadata_-_New_datasets | here]] for new datasets and [[Cross_Archive_Metadata_-_Legacy_datasets | here]] for legacy datasets.

==== Reporting the Radiocarbon measurements ====

{| class="wikitable"
|-
|+Table 2. Essential/Recommended/Desired metadata for reporting radiocarbon measurements
|-
! Metadata|| Essential (E)/Recommended(R)/Desired (D) || Reason/Notes || Added by (optional)
|-
| Chemical pretreatment/preparation || E|| oxidation, chemical leach (%), a/b/a, soxhlet, ultrafiltration, none, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|[[:Property:Method (L)| Method]] || E || GPC, LSC, AMS, etc || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Laboratory ID# || E || eg. OS####; CAMS####; QUB#### || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| δ{{SimpleNuclide2|Carbon|13}} ratio actual/estimated (PDB/V-PDB) || R || Note, the AMS measured {{SimpleNuclide2|Carbon|13}} has low precision (a few per mil, compared to IRMS). Most AMS labs do NOT report the machine measured {{SimpleNuclide2|Carbon|13}} value because it is frequently misused. This should be estimated as per SP77 <ref name = SP77 /> or an IRMS-based value/estimate. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Conventional radiocarbon age as years BP || E || Note, that by definition, conventional radiocarbon age is the Libby based age. || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| one-sigma standard deviation || E || one-sigma standard deviation || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 15:37, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| F14C ({{SimpleNuclide2|Carbon|13}} and background correction applied) || E || This is slightly different than Stuiver and Polach <ref name = SP77 /> who have "D14C" as the optional parameter.
We suggest the inclusion of the background and d13C corrected Fraction modern (F14C) as it is the primary reported value. In the past there has been some inconsistencies in the literature/laboratories with regards to fraction modern. By using/requesting F14C you will be explicitly requesting {{SimpleNuclide2|Carbon|13}} and background corrected Fraction Modern (aka F14C, as per Reimer et al.[2004]) as intended by SP77.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| colspan = '4' |''Correction applied to radiocarbon date prior to, or during conversion to calibrated age''
|-
| colspan = '4' |''Marine Reservoir effect''
|-
| Marine reservoir age, , ± one-sigma sd (or square root of the variance) uncertainty, reference/source ||E|| || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
|<math>\Delta R</math> value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source || E || || [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| other corrections: value ({{SimpleNuclide2|Carbon|14}} years), ± one-sigma sd (or square root of var), reference/source ||E|| ||[[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|-
| Calibration or conversion to calibrated ages || ||
As of present, the international radiocarbon community recommends the use of the INTCAL13 (aka Marine 13<ref>P. J. Reimer et al., 2013. INTCAL13 and MARINE13 Radiocarbon age calibration curves, 0-50,000 years CAL BP. Radiocarbon, 55, 1869-1887.</ref>) and SHCAL13 <ref>A. G. Hogg, et al., 2013. SHCal13 Southern Hemisphere calibration, 0-50,000 years cal BP. Radiocarbon 55, 1889-1903.</ref> data products. Calibration of post-bomb (post 1954/1957) samples should also include the calibration data-set utilized, description/reference of any corrections applied, and the software/algorithm utilized to convert the F14C data to years AD.
|| [[User:Khider|Deborah Khider]] ([[User talk:Khider|talk]]) 16:13, 15 March 2017 (PDT) on behalf of T Guilderson
|}

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll Radiocarbon chemicalpretreatment.jpeg|thumb|300px|Results of the poll conducted on Twitter between March 27th 2017 and April 3rd 2017]]

<poll>
For Radiocarbon measurements, the chemical pretreatment/preparation of the sample should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll Radiocarbon Method.png|400px|thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the method should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

[[File:TwitterPoll Radiocarbon LabID.png | 400px |thumb|right|Results of the poll placed on Twitter between July 12th and 19th 2017]]

<poll>
For radiocarbon measurements, the laboratory ID# should be:
Essential metadata
Recommended metadata
Desired metadata
</poll>

<poll>
For radiocarbon measurements, the d13C ratio actual/estimated should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, conventional radiocarbon age as years BP should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the 1-sigma standard deviation on the conventional radiocarbon age should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the F14C should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the marine reservoir age, one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements converted to calendar ages, the DELTA_R value, ± one-sigma sd (or square root of the variance) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For radiocarbon measurements, the hard/soft water effect: value, ± one-sigma sd (or square root of var) uncertainty, reference/source should be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== Lead ===

Proposed standards from [https://dornsife.usc.edu/cf/faculty-and-staff/faculty.cfm?pid=1003326 Doug Hammond] (University of Southern California).

{| class="wikitable"
|-
|+ Recommendation to report 210Pb measurements
|-
! Metadata || Description || Essential (E)/ Recommended (R)/ Desired (D)
|-
| calculated excess 210Pb values || Total - supported || E for both New and Legacy datasets
|-
| 226Ra || The supported 210Pb || D for both new and legacy datasets
|-
| Total 210Pb || || D for both new and legacy datasets
|-
| Whether a salt correction is made || || D for both new and legacy datasets
|-
| Porosity || necessary to do a salt correction || D for both new and legacy datasets
|-
| Measurement methodology || alpha spectrometry, gamma spectrometry... || R for both new and legacy datasets
|-
| Units || Recommend to report units in Bq/kg ||
|-
| rowspan = "3"|Depth || A way to locate where on the archive the measurements was made || E
|-
| mid-depth || E for both new and legacy datasets
|-
| interval top/bottom || R for both new and legacy datasets
|-
| core collectionDate || Necessary to convert the excess 210Pb values to calendar age
Recommend to correct the reported activities to the collectionDate
|| E for both new and legacy datasets
|-
| Methodology used to calculate age || || E for both new and legacy datasets
|}

The same standards (excluding supporting measurements, which do not apply) are proposed for 137Cs measurements which are often made alongside 210Pb.

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll 210Pb ExcessValues.png | 400px | right| thumb | Results of the poll placed on Twitter between July 17th-24th 2017]]

<poll>
Should the calculated excess 210Pb values be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb Supportedactivties.png|400px|thumb|right|Results of the poll placed on Twitter from March 30th to April 6th 2017]]

<poll>
Should the supported activities (226Ra) be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb totalMeasured.png | 400px |thumb | right | Results of the poll placed on Twitter from July 17th to 24th]]

<poll>
Should the measured total 210Pb be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

[[File:TwitterPoll 210Pb SaltCorrection.png | 400px | right |thumb| Results of the poll placed on Twitter between July 17th and 24th 2017]]

<poll>
For 210Pb chronologies, should the reporting of a salt correction be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive porosity be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the measurement methodology be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the activities be reported in:
Bq/kg
other
No imposed units but units should be reported
</poll>

<poll>
For 210Pb chronologies, should depth be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the archive collectionDate be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
For 210Pb chronologies, should the method used to convert to calendar age be considered:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

=== U-series ===
A standard was recently proposed by Dutton et al [2017]<ref>A. Dutton, K. Rubin, N. McLean, J. Bowring, E. Bard, R.L. Edwards, G.M. Henderson, M.R. Reid, D.A. Richards, K.W.W. Sims, J.D. Walker, Y. Yokoyama, Data reporting standards for publication of U-series data for geochronology and timescale assessment in the earth sciences, Quaternary Geochronology, Volume 39, April 2017, Pages 142-149, [http://doi.org/10.1016/j.quageo.2017.03.001 DOI]</ref>. We suggest to re-use it wholesale.

== Layer-counted chronologies ==

Comboul et al<ref>Comboul, M., J. Emile-Geay, M. N. Evans, N. Mirnateghi, K. M. Cobb, and D. M. Thompson (2014), A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives, Climate of the Past, 10(2), 825–841, doi:10.5194/cp-10-825-2014</ref> argue that it is critical to report uncertainties in layer-counted chronologies, and that these can be expressed in terms of an undercounting and overcounting rate. However, there needs to be agreement about how to measure and report this rate for various archives.

=== Varves ===

=== Growth rings ===
Trees, corals, speleothems

Tree-rings typically provide an absolute chronology but there needs to be the facility to also work with 'floating' chronologies anchored typically by radiocarbon. A hybrid dendro-radiocarbon chronological framework should be supported.

Tree-rings data can also be stored at subannual level e.g. with early and latewood parameters. These are typically stored as two different data series as they are normally used to reconstruct different climatic parameters. In chronological terms these datasets represent portions of the year but precisely which portions depends on the species and location. In the southern hemisphere the earlywood will typically grow in the final months of the year and the latewood the first months of the following year. For paleoclimate reconstructions it's therefore essential to include metadata regarding the months each data point covers.

A convention that continues to cause confusion when representing dendrochronological data is the use of the astronomical calendar. The astronomical calendar includes the year 0 so matches the AD calendar, but is one year different in the BC period. Astronomical dates are easier to handle in statistical analyses but have been erroneously quoted as BC years in even some very prestigious articles. Whatever method is used, it should be clear and consistent.

=== Ice layers ===
Role of flow models.

== Age-modeling software ==

Content:
* method (e.g. Bacon, OxCal, BChron, BAM)
* version
* parameters

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

[[File:TwitterPoll AgeModeling Software.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
Should the method by which the chronology is obtained be fully documented
with the data
in the paper only
both with the data and in the paper
</poll>

[[File:TwitterPoll PublicationSoftwareChronology.png | thumb | 400px | right | Results of the poll placed on Twitter between April 25th and May 2nd 2017]]

<poll>
If documented with the data, should the publication information about the software used in the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data, should the code (i.e. parameters used) used for the chronology be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble age models be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

<poll>
If documented with the data and using a technique creating ensembles of possible age models, should the ensemble statistics (e.g., mean, median, standard deviation, quantiles) be:
Essential Metadata
Recommended Metadata
Desired Metadata
</poll>

== Polls ==

'''Note''': Do not edit the polls (even for typos) once voting has started as it will reset the vote counts to zero. If a change needs to be made, make an annotation above the old poll (i.e., above the poll tags) and place the new poll below the first one.

Here are polls that the group might want to consider:

For '''LEGACY DATASETS''':
<poll>
Should legacy chronologies be updated to the current field standard (e.g. chronologies obtained from IntCal09 should be redone with IntCal13)?
Yes, if raw data is available
No, but put a warning on the chronologies
No
</poll>

==References==
<references \>

PAGES2k

2017-07-25T03:04:35Z

Jeg: Set PropertyValue: PublishedIn (L) = Publication.10.1038/sdata.2017.88

[[Category:Compilation (L)]]{{#set:
Author (L)=J._Emile-Geay|
Author (L)=Nick_McKay|
Author (L)=Darrell|
Author (L)=Lucien_von_Gunten|
Author (L)=Kevin_Anchukaitis|
Author (L)=PAGES2k_consortium|
CompilationCitation (L)=PAGES2k Consortium, A global multiproxy database for temperature reconstructions of the Common Era, Scientific Data, in press|
CompilationVersion (L)=2.0.0|
FundedBy (L)=National_Science_Foundation.ICER-1541029|
HasLink (L)=http://www.ncdc.noaa.gov/paleo-search/study/21171|
HasLink (L)=https://figshare.com/s/d327a0367bb908a4c4f2|
ModeledBy (L)=PAGES2k.Model1|
PublishedIn (L)=Publication.10.1038/sdata.2017.88}}

__NOCACHE__
[[File:PAGES2k-network-logo.png|thumb|right|alt=PAGES2k logo]]

== Description ==
Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. The '''PAGES2k Phase 2 collection''' is a community-sourced compilation of temperature-sensitive proxy records associated with the [http://www.pages-igbp.org/ini/wg/2k-network/intro PAGES2k initiative]. The (soon to be published) database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial vs marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era.

== Revisions and updates ==
Revisions happen continually on the wiki, and are tracked by the system. When changes are substantive enough that new releases are warranted, they will be explained here by a change log.

The PAGES2k versioning scheme is as follows: the version number for a data compilation is of the form C1.C2.C3, where C1 is a counter associated with a publication of the dataset, C2 is a counter updated every time a record is added or removed, and C3 is a counter updated every time a modification is made to the data or metadata in an individual record.

== How to cite ==
This section should encourage users to include multiple citations for each of the records: (a) the original publication where the data are described; (b) the data citation to the raw dataset; (c) the data citation to any modified versions of the dataset. In addition, (d) if users rely on metadata or other features of the compilation, they should cite the PAGES2k data product. This section should explain the principles of tracking and attributing data and provide a link to that informs users about data citations.

== Downloads ==
The data are available on this wiki as LiPD files.
Additionally, the data will be made available on [https://doi.org/10.6084/m9.figshare.c.3285353 FigShare] and at the [http://www.ncdc.noaa.gov/paleo-search/study/21171 National Center for Environmental Information/World Data Service for Paleoclimatology]

== Datasets in the PAGES2k database ==



{{ #ask:
[[Category:Dataset_(L)]]
[[IncludesPaleoData_(L).FoundInMeasurementTable_(L).IncludesVariable_(L).InCompilation:: PAGES2k_v1.12.0]]
| ?ArchiveType=ArchiveType
| format=broadtable
| limit=20
}}{{#subobject:_QUERY828b4b9c541e880cdace32132f7896ac}}

PAGES2k

2017-07-23T04:43:32Z

Jeg: Set PropertyValue: HasLink (L) = https://figshare.com/s/d327a0367bb908a4c4f2

[[Category:Compilation (L)]]{{#set:
Author (L)=J._Emile-Geay|
Author (L)=Nick_McKay|
Author (L)=Darrell|
Author (L)=Lucien_von_Gunten|
Author (L)=Kevin_Anchukaitis|
Author (L)=PAGES2k_consortium|
CompilationCitation (L)=PAGES2k Consortium, A global multiproxy database for temperature reconstructions of the Common Era, Scientific Data, in press|
CompilationVersion (L)=2.0.0|
FundedBy (L)=National_Science_Foundation.ICER-1541029|
HasLink (L)=http://www.ncdc.noaa.gov/paleo-search/study/21171|
HasLink (L)=https://figshare.com/s/d327a0367bb908a4c4f2|
ModeledBy (L)=PAGES2k.Model1|
PublishedIn (L)=PAGES2k_SD2017}}

__NOCACHE__
[[File:PAGES2k-network-logo.png|thumb|right|alt=PAGES2k logo]]

== Description ==
Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. The '''PAGES2k Phase 2 collection''' is a community-sourced compilation of temperature-sensitive proxy records associated with the [http://www.pages-igbp.org/ini/wg/2k-network/intro PAGES2k initiative]. The (soon to be published) database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial vs marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era.

== Revisions and updates ==
Revisions happen continually on the wiki, and are tracked by the system. When changes are substantive enough that new releases are warranted, they will be explained here by a change log.

The PAGES2k versioning scheme is as follows: the version number for a data compilation is of the form C1.C2.C3, where C1 is a counter associated with a publication of the dataset, C2 is a counter updated every time a record is added or removed, and C3 is a counter updated every time a modification is made to the data or metadata in an individual record.

== How to cite ==
This section should encourage users to include multiple citations for each of the records: (a) the original publication where the data are described; (b) the data citation to the raw dataset; (c) the data citation to any modified versions of the dataset. In addition, (d) if users rely on metadata or other features of the compilation, they should cite the PAGES2k data product. This section should explain the principles of tracking and attributing data and provide a link to that informs users about data citations.

== Downloads ==
The data are available on this wiki as LiPD files.
Additionally, the data will be made available on [https://doi.org/10.6084/m9.figshare.c.3285353 FigShare] and at the [http://www.ncdc.noaa.gov/paleo-search/study/21171 National Center for Environmental Information/World Data Service for Paleoclimatology]

== Datasets in the PAGES2k database ==



{{ #ask:
[[Category:Dataset_(L)]]
[[IncludesPaleoData_(L).FoundInMeasurementTable_(L).IncludesVariable_(L).InCompilation:: PAGES2k_v1.12.0]]
| ?ArchiveType=ArchiveType
| format=broadtable
| limit=20
}}{{#subobject:_QUERY828b4b9c541e880cdace32132f7896ac}}

Main Page

2017-07-13T08:15:22Z

Jeg: /* Working with LiPD Datasets */

[[File:EarthLinked_Banner_blue_NoShadow.jpg|center|440px|alt=LinkedEarthLogo]]

__NOCACHE__

<div style = "text-align:center;">Welcome to the LinkedEarth Wiki!</div>

The LinkedEarth wiki is an [https://earthcube.org EarthCube]-funded platform that:
#enables the curation of publicly-accessible database by paleoclimate experts, and
#fosters the development of standards, so paleoclimate data are easier to analyze, share, and re-use. 

==Getting started with LinkedEarth==

<gallery mode = "packed-overlay" widths=150px heights=100px>
File:JoinUsIcon MainPage.png | [http://linked.earth/aboutus/membership/ Join LinkedEarth]
File:GettingStartedIcon MainPage.png | [[Get_Started_with_the_LinkedEarth_wiki | StartUp Guide]]
File:Browse The Wiki.png | [[Special:random | Browse existing pages]]
</gallery>

Several tutorials are also available on our [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel]!

==Community Activities==

Join a [[:Category:Working Group | working group]] (WG) and participate in the discussion about [[Paleoclimate_Data_Standards | paleoclimate data standards]].

'''New''': Each working group has polls waiting for community input. ''You must be logged in to vote.''

In the Linked Earth context, a WG is a self-organized coalition of knowledgeable experts who elaborate and discuss the components of a [[Paleoclimate_Data_Standards | data standard]] for their topic(s) of interest. WGs may be created by any member of the LinkedEarth community. Currently, the LinkedEarth community is organized around {{PAGESINCATEGORY:Working Group}} working groups.

'''To join a WG, do so on your LinkedEarth wiki profile page'''.

<gallery mode = "packed-overlay" widths=150px heights=150px>
File:Open_data_standards_trim.png | [[Paleoclimate Data Standards]]
File:WorkingGroups MainPage Icons.png | [[:Category:Working Group | Join a Working Group]]
File:Ontology_wordcloud.png | [[LinkedEarth Ontology]]
</gallery>

== Contribute Datasets ==

We recommend using the [[Linked Paleo Data | LiPD]] format to get your data on the wiki. The Python [[LiPD Utilities]] allow to create a LiPD from an Excel template, wich can be downloaded [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx here]. For instructions on filling out this template, see the page "[[Creating a LiPD file]]".

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[Creating a LiPD file]]
File:ExcelLogo.png | [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx LiPD Template]
File:AnnotateDatasetImage.png | [[Dataset Tutorial | Upload a LiPD dataset]]
File:BrowseIcon.png| [[MD982181.Khider.2014 | Browse a dataset]]
</gallery>

== Working with LiPD Datasets ==

{{See also|Using LiPD files}}

The [[LiPD Utilities]] (available in R, Python, and Matlab) allow to read/write LiPD files, extract and collapse timeseries objects, and filter datasets according to your search criteria. Data analysis packages are currently available in R ([[GeoChronR]]) and Python ([[Pyleoclim]]). A large body of [https://github.com/CommonClimate/PAGES2k_phase2 Matlab code exists already] to analyze the [[PAGES2k]] dataset.

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[LiPD Utilities]]
File:RLogo.jpeg | [[GeoChronR]]
File:PythonLogo.jpg | [[Pyleoclim]]
</gallery>

==Current State of the Database==

The LinkedEarth Wiki currently contains '''{{PAGESINCATEGORY:Dataset (L)}} datasets''', mostly from the [[PAGES2k]] compilation. We are in the process of adding more Holocene records, as well as >100 deep-sea cores from the LR04 benthic stack compilation. Please contact us if you want to lead a '''data drive''' to flesh it out some more.

=== Dataset Location ===



{{#ask: [[Category:Dataset_(L)]]
| ?CollectedFrom_(L).Coordinates
| ?Name_(L)
| ?ArchiveType
| markercluster=on
| showtitle=off
| zoom=1
| searchmarkers=all
| maxzoom=14
| minzoom=1
| limit=1000
| height=510
| template=LiPDLocation
| format=leaflet
}}

=== Recently Contributed Datasets ===

{{#ask: [[Category:Dataset (L)]]
| ?CollectedFrom (L).CoordinatesFor=LiPD Dataset
| ?ArchiveType
| ?CollectedFrom (L).Coordinates
| mainlabel=-
| limit=10
| format=broadtable
| sort=Modification date
| order = descending
}}

=== Search the Database by Archive===



<gallery mode = "packed-overlay" widths=200px heights=200px>
File:Coral_Archive_200px.jpg | [[:Category:Coral | Coral]]
File:Documents_Archive_200px.jpg | [[:Category:Document | Document]]
File:GlacierIce_Archive_200px.jpg | [[:Category:GlacierIce | Glacier Ice]]
File:Lake_Archive_200px.jpg | [[:Category:LakeSediment | Lake Sediment]]
File:MarineSediment_Archive_200px.jpg | [[:Category:MarineSediment | Marine Sediment]]
File:Mollusk_Archive_200px.jpg | [[:Category:MolluskShells | Mollusk Shells]]
File:Peat_Archive_200px.jpg | [[:Category:Peat | Peat]]
File:Sclerosponge_Archive_200px.jpg | [[:Category:Sclerosponge | Sclerosponge]]
File:Speleothem_Archive_200px.jpg | [[:Category:Speleothem | Speleothem]]
File:Wood_Archive_200px.jpg | [[:Category:Wood | Wood]]
</gallery>

== More about LinkedEarth ==

Website: [http://linked.earth LinkedEarth Website]

Social Media: [https://www.facebook.com/LinkedEarth-1018909201501056/?fref=ts Facebook] | [https://twitter.com/Linked_Earth Twitter] | [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel] | [https://github.com/LinkedEarth GitHub]

Weekly Digest

2017-07-13T08:04:39Z

Jeg: Removed newsletter terminology

== Activity from 2017.Jul.06 00.00AM to 2017.Jul.13 00.00AM ==

During the last 7 days: 
2 new datasets; 
10 new persons; 
0 new working groups were created. 
 Congratulations to [http://wiki.linked.earth/User:Dclund Dclund] for being the top contributor with 201 contributions this week! Congratulations also to our top contributors: 2. [http://wiki.linked.earth/User:Khider Khider] has 30 contributions. 3. [http://wiki.linked.earth/User:Jeg Jeg] has 1 contributions. 4. [http://wiki.linked.earth/User:KMicha KMicha] has 1 contributions. Here are the updated working groups: <div>[http://wiki.linked.earth/Category:Historical_Documents_Working_Group Historical_Documents_Working_Group] has 1 new contributions; </div> Here are newly added datasets: <div>[http://wiki.linked.earth/KNR-159-5_33GGC.Lacerra.2017 KNR-159-5_33GGC.Lacerra.2017] [http://wiki.linked.earth/KNR-159-5_78GGC.Lacerra.2017 KNR-159-5_78GGC.Lacerra.2017] </div> Here are other modified pages: <div>[http://wiki.linked.earth/Lund Lund] [http://wiki.linked.earth/D._C._Lund D._C._Lund] [http://wiki.linked.earth/A._C._Tessin A._C._Tessin] [http://wiki.linked.earth/Andreas_Schmittner Andreas_Schmittner] [http://wiki.linked.earth/Jimin_Yu Jimin_Yu] [[#more-other-links|More modified links are at the bottom.]]</div> More modified links: [http://wiki.linked.earth/David_Lund David_Lund] [http://wiki.linked.earth/Matthew_Lacerra Matthew_Lacerra] [http://wiki.linked.earth/Dclund Dclund] [http://wiki.linked.earth/Charles_E._Lawrence Charles_E._Lawrence] [http://wiki.linked.earth/Seonmin_Ahn Seonmin_Ahn]

GeoChronR

2017-07-08T07:23:43Z

Jeg: Set PropertyValue: HasLink (L) = https://github.com/nickmckay/GeoChronR

[[Category:SoftwareCode (L)]]{{#set:
HasExecutionEnvironment (L)=R|
HasLink (L)=https://github.com/nickmckay/GeoChronR|
HasVersion=0.1|
Name (L)=GeoChronR}}

Main Page

2017-07-04T14:06:59Z

Jeg: included EarthCube reference at the top

[[File:EarthLinked_Banner_blue_NoShadow.jpg|center|440px|alt=LinkedEarthLogo]]

<div style = "text-align:center;">Welcome to the LinkedEarth Wiki!</div>

The LinkedEarth wiki is an [https://earthcube.org EarthCube]-funded platform that:
#enables the curation of publicly-accessible database by paleoclimate experts, and
#fosters the development of standards, so paleoclimate data are easier to analyze, share, and re-use. 

==Getting started with LinkedEarth==

<gallery mode = "packed-overlay" widths=150px heights=100px>
File:JoinUsIcon MainPage.png | [http://linked.earth/aboutus/membership/ Join LinkedEarth]
File:GettingStartedIcon MainPage.png | [[Get_Started_with_the_LinkedEarth_wiki | StartUp Guide]]
File:Browse The Wiki.png | [[Special:random | Browse existing pages]]
</gallery>

Several tutorials are also available on our [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel]!

==Community Activities==

Join a [[:Category:Working Group | working group]] (WG) and participate in the discussion about [[Paleoclimate_Data_Standards | paleoclimate data standards]].

'''New''': Each working group has polls waiting for community input. ''You must be logged in to vote.''

In the Linked Earth context, a WG is a self-organized coalition of knowledgeable experts who elaborate and discuss the components of a [[Paleoclimate_Data_Standards | data standard]] for their topic(s) of interest. WGs may be created by any member of the LinkedEarth community. Currently, the LinkedEarth community is organized around {{PAGESINCATEGORY:Working Group}} working groups.

'''To join a WG, do so on your LinkedEarth wiki profile page'''.

<gallery mode = "packed-overlay" widths=150px heights=150px>
File:Open_data_standards_trim.png | [[Paleoclimate Data Standards]]
File:WorkingGroups MainPage Icons.png | [[:Category:Working Group | Join a Working Group]]
File:Ontology_wordcloud.png | [[LinkedEarth Ontology]]
</gallery>

== Contribute Datasets ==

We recommend using the [[Linked Paleo Data | LiPD]] format to get your data on the wiki. The Python [[LiPD Utilities]] allow to create a LiPD from an Excel template, wich can be downloaded [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx here]. For instructions on filling out this template, see the page "[[Creating a LiPD file]]".

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[Creating a LiPD file]]
File:ExcelLogo.png | [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx LiPD Template]
File:AnnotateDatasetImage.png | [[Dataset Tutorial | Upload a LiPD dataset]]
File:BrowseIcon.png| [[MD982181.Khider.2014 | Browse a dataset]]
</gallery>

== Working with LiPD Datasets ==

{{See also|Using LiPD files}}

The [[LiPD Utilities]], available in R, Python, and Matlab allows to read/write LiPD files, extract and collapse timeseries objects, and filter datasets according to your search criteria. Data analysis packages are currently available in R ([[GeoChronR]]) and Python ([[Pyleoclim]]). A large body of [https://github.com/CommonClimate/PAGES2k_phase2 Matlab code exists already] to analyze the [[PAGES2k]] dataset.

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[LiPD Utilities]]
File:RLogo.jpeg | [[GeoChronR]]
File:PythonLogo.jpg | [[Pyleoclim]]
</gallery>

==Current State of the Database==

The LinkedEarth Wiki currently contains '''{{PAGESINCATEGORY:Dataset (L)}} datasets''', mostly from the [[PAGES2k]] compilation. We are in the process of adding more Holocene records, as well as >100 deep-sea cores from the LR04 benthic stack compilation. Please contact us if you want to lead a '''data drive''' to flesh it out some more.

=== Dataset Location ===



{{#ask: [[Category:Dataset_(L)]]
| ?CollectedFrom_(L).Coordinates
| ?Name_(L)
| ?ArchiveType
| markercluster=on
| showtitle=off
| zoom=1
| searchmarkers=all
| maxzoom=14
| minzoom=1
| limit=1000
| height=510
| template=LiPDLocation
| format=leaflet
}}

=== Recently Contributed Datasets ===

{{#ask: [[Category:Dataset (L)]]
| ?CollectedFrom (L).CoordinatesFor=LiPD Dataset
| ?ArchiveType
| ?CollectedFrom (L).Coordinates
| mainlabel=-
| limit=10
| format=broadtable
| sort=Modification date
| order = descending
}}

=== Search the Database by Archive===



<gallery mode = "packed-overlay" widths=200px heights=200px>
File:Coral_Archive_200px.jpg | [[:Category:Coral | Coral]]
File:Documents_Archive_200px.jpg | [[:Category:Document | Document]]
File:GlacierIce_Archive_200px.jpg | [[:Category:GlacierIce | Glacier Ice]]
File:Lake_Archive_200px.jpg | [[:Category:LakeSediment | Lake Sediment]]
File:MarineSediment_Archive_200px.jpg | [[:Category:MarineSediment | Marine Sediment]]
File:Mollusk_Archive_200px.jpg | [[:Category:MolluskShells | Mollusk Shells]]
File:Peat_Archive_200px.jpg | [[:Category:Peat | Peat]]
File:Sclerosponge_Archive_200px.jpg | [[:Category:Sclerosponge | Sclerosponge]]
File:Speleothem_Archive_200px.jpg | [[:Category:Speleothem | Speleothem]]
File:Wood_Archive_200px.jpg | [[:Category:Wood | Wood]]
</gallery>

== More about LinkedEarth ==

Website: [http://linked.earth LinkedEarth Website]

Social Media: [https://www.facebook.com/LinkedEarth-1018909201501056/?fref=ts Facebook] | [https://twitter.com/Linked_Earth Twitter] | [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel] | [https://github.com/LinkedEarth GitHub]

Talk:Holocene Sea Surface Temperature

2017-07-04T13:58:33Z

Jeg: /* suggested name -- ~~~~ */ new section

== suggested name -- [[User:Jeg|JEG]] ([[User talk:Jeg|talk]]) 06:58, 4 July 2017 (PDT) ==

can we call it HoloSST?

Paleoclimate Data Standards

2017-07-04T13:15:01Z

Jeg: /* Science Drivers */

= Background =
== What is a standard? ==
[http://www.earthcube.org/document/2015/ecstandardsrecs EarthCube defines] a standard as follows:

a public specification documenting some practice or technology that is adopted and used by a community. [..] There is a continuum starting with any documented practice in some community. If lots of people use a particular documented practice it could be adopted as a best practice. If almost everyone uses some documented practice, then it is a de facto standard.

Notice the emphasis on community and on practice. If only person uses a technical specification, it's not a standard. If it's voted on but not applied in practice, it's worthless as well. Thus, the objective of this EarthCube activity is to propose a standard with broad community appeal and adoption.

== Why do we need standards? ==
Modern life would simply be unlivable without standards. Imagine having to use a separate browser for each web page your visit, or a separate power-transmission system for every appliance you use! You only have to travel to a country that uses a different electric plug than the one your computer and phone employ to appreciate what a nightmare that would be. In science, the ultimate objective of a standard is to make data understandable by others (including machines), and the derived analyses reproducible. Thus, a key objective of LinkedEarth is to promote the development of a community standard for paleoclimate data. Indeed, despite some ad-hoc gatherings among communities of interest over many years, until recently there had never been a concerted effort to produce a standard applicable to all paleoclimate observations. Given the increased importance of synthesis work (e.g. PAGES2k, Shakun et al 2012, Marcott et al 2013, MARGO, others), it is increasingly important that a common solution be found.

= Prior Work =
== Pre-2016 ==
Here is a non-exhaustive list of past discussions that we are aware of:

* [[media: Reporting_Standards_for_Paleoceanographic_PMIP3_Dec2013.docx | PMIP3 Workshop in Corvallis]] (December 2013)
* [http://www.clivar.org/sites/default/files/documents/TriesteReport_nov5.pdf report for the workshop "REPRESENTING AND REDUCING UNCERTAINTIES IN HIGH-RESOLUTION PROXY CLIMATE DATA"] (Trieste, Italy, June 2008)

We welcome any summaries of prior discussions on data standards you may have had at meetings, workshops. To do so, either link to a document that you have uploaded on the wiki or create a new page and list it here.

== LiPD ==
The [[Linked_Paleo_Data|LiPD]] format embodies one part of this solution: it offers a container that can wrap tightly around a wide varieties of paleoclimate [[:Category:Dataset (L)|datasets]], providing a vessel for paleoclimate content. Other formats, of course, would be acceptable; however, there is no viable alternative currently in existence, which is why [[Nicholas_McKay | Nick]] and [[J._Emile-Geay | Julien]] had to go through the trouble of inventing such a format. Another reason to adopt it is that '''there is a growing code ecosystem being developed around LiPD''' in Matlab, R and Python: the [https://github.com/nickmckay/LiPD-utilities LiPD utilities] that allow cross-walk between all kinds of commonly-used formats, [http://nickmckay.github.io/GeoChronR/ GeoChronR] for the analysis of time-uncertain paleo data, and [https://github.com/LinkedEarth/Pyleoclim_util Pyleoclim] to visualize and analyze the data.
Why not just stick with LiPD and call it a day, you ask? Well, LiPD's infinite flexibility is a double-edge sword: it can accommodate all manner of information, but that information may or may not align with community best practices. It is thus '''necessary for the community to decide on such practices'''. In other words, if LiPD provides a field-tested answer to the question: ''how should paleoclimate data be stored?'', it says nothing about '''''what''''' should be stored: that decision is up to the community.

== First workshop on paleoclimate data standards ==
The [[PDS_workshop_2016 | 2016 workshop on paleoclimate data standards]] (PDS workshop, for short) served as a stepping stone to initiate a broader process of community engagement and feedback elicitation, with the goal of generating such a community-vetted standard. The workshop identified a need to '''delineate a set of essential, recommended and desired properties for each dataset'''.
By default, any and all information is desired. A subset of that should be recommended to ensure optimal re-use. Yet a smaller subset of that is '''essential''' in the sense that a paleoclimate data set should not be acceptable without this information (for more details, see the [[PDS_workshop_2016 | PDS workshop page]]). Four additional themes emerged:

=== Cross-Archive Standards ===
Some essential data/metadata are shared among all conceivable archive types:

* '''A table with at least two columns''', one representing time, the other a climate indicator of some sort
* '''Geolocation''': coordinates, polygons, or, in cases where coordinates or polygons cannot be given, general location info
* '''Source''': PI, contributor, or database (first author of publication if published, or some other person who can speak for the dataset if not published/if the first author is no longer in science/etc)
* '''Names''' and '''Units''' of the variables in the dataset

=== Archive-specific standards ===
What is needed to intelligently re-use a marine-annually resolved record could be quite different than what is needed to intelligently re-use an ice core record, for instance. Therefore, these these levels are archive-specific.

=== Legacy vs Modern datasets ===
The group also recognized that standards need to be more stringent for modern datasets than for legacy datasets, for which some (meta)data are sometimes impossible to procure (think: raw radiocarbon dates from a PI now deceased). Thus, for every archive and across archives, there needs to be different set of standards for both kinds.
What constitutes "legacy" data is also open to interpretation, and requires a formal definition (and a vote).

=== Audience and Purpose ===
Finally, it was recognized that all of the above considerations are a function of who is using the data, and for what purpose. As such, it is useful to consider a few science drivers.

= Science Drivers =
One possible way to elaborate a standard is to ask oneself: "What pieces of metadata would I require to reproduce this particular dataset and therefore which one should I provide for my own datasets?" Some of these metadata will be standard across all archives (i.e., geographic coordinates, publication information). Some will be specific to each archive or observation type. See [[:Category:Marine_Sediment_Working_Group | here]] for an example of such discussions on foraminiferal Mg/Ca.

== Querying the datasets ==

Another way to think about the essential/recommended/optional metadata is to think about the kind of queries one would want to enable for their research. For instance, a recent study on [http://linked.earth/wp-content/uploads/2016/01/Khider_AGUFall16.pdf Testing the Millennial-Scale Solar-Climate Connection in the Indo-Pacific Warm Pool] required the following queries and associated metadata:

{| class="wikitable"
|-
! Query || Required Metadata
|-
| SST-sensitive proxies (i.e. Mg/Ca, Uk37 and TEX86) || Needed a property describing the proxy observations as well as a standard to express the concept of Mg/Ca, TEX86 and UK37. This need gave rise to [[:Property:ProxyObservationType_(L)]] and terms in the ontology [[:Category:ProxyObservation_(L)]] to describe these concepts.
|-
| Holocene data (0-10ka) spanning at least 5kyr || Needed a property describing the concept of [[Age]], giving rise to [[:Property:InferredVariableType (L)]]. An ontology for [[:Category:InferredVariable_(L)]] is in progress. It also became obvious that we needed to standardize the way to represent time and the units of time. Furthermore, since the wiki doesn't read the content of the .csv file, some metadata about the values stored in the .csv file were also needed. We therefore created the following properties: [[:Property:HasMinValue (L)]], [[:Property:HasMaxValue (L)]], [[:Property:HasMeanValue (L)]].
|-
| In the IndoPacific Warm Pool || We needed to query the dataset by latitude/longitude.
|}

Other types of basic query include searching for a particular publication, using either the DOI, title, journal, authors, and searching by [[:Category:ProxyArchive_ (L) | archiveType]]. The latter is currently used to obtain the maps under each archive category (for example, [[:Category:MarineSediment | marine sediments]]). Enter the queries you'd like to perform, and the metadata required to perform them.

== Analyzing the datasets ==

Finally, this problem can be approached from a data analysis point-of-view. "Given my interest, what are the required information I would need to perform my analysis?"

For instance, if all is known about a dataset are the geographical coordinates from which the archive was taken, then the only possible analysis is to create a location map of said archive (with or without its nearest neighbor contained in the database). On the other hand, if an age and paleo variable are contained within the PaleoDataTable, the resulting time series can be used for correlation analysis and spectral analysis. However, without the raw age data, it would be impossible to recalibrate the record using updated techniques, limiting its usefulness. To ask the most questions of our datasets, and do the best science, we need them to be as complete as possible.

For the Holocene study, the datasets had to contain the raw radiocarbon measurements for use with [https://cran.r-project.org/web/packages/Bchron/vignettes/Bchron.html Bchron]. [http://linked.earth/doing-science-with-linkedearth/ this blog post] describes how richer and standardized metadata supported the study. This [https://github.com/khider/Holocene-Millennial-Scale-Variability/blob/master/AGU%20Fall%202016/Holocene_MillennialScaleVar.md Jupyter Notebook] integrates code, data and text to walk you through the story. None of this would have been possible without [[Linked_Paleo_Data|LiPD]].

= Process for achieving a paleoclimate data standard=
== Working Groups ==
Attendees of the [[PDS workshop 2016]] proposed that archive-centric [[:Category:Working_Group | working groups]] (WGs; self-assembled coalitions of knowledgeable experts) would be best positioned to elaborate and discuss the components of a data standard for their specific sub-field of paleoclimatology. It is also critical to ensure interoperability between standards to enable longitudinal (multiproxy) investigations.
[[:Category:Working_Group | Working groups]] have been formed and are now being consulted to generate the backbone of a standard, which will be presented to the community at the [http://www.pages-osm.org PAGES OSM meeting] in Zaragoza (May 9-13, 2017).

== International Partners ==
This process contributes to the [http://pastglobalchanges.org/ini/int-act/data-stewardship data stewardship initiative] of our [http://www.pages-igbp.org/about/general-overview PAGES/Future Earth] partners. Therefore, we are working together with PAGES to reach out to the broadest cross-section of paleoscientists and invite them to contribute to the process. The end goal is a standard to be precisely documented and adopted by LinkedEarth and PAGES. The standard will be implemented in all LinkedEarth activities and proposed for adoption by [http://earthcube.org/ EarthCube], the [https://rd-alliance.org/ Research Data Alliance], the [http://www.esipfed.org/ Federation of Earth Science Information Partners], [https://www.ncdc.noaa.gov/data-access/paleoclimatology-data NOAA WDS-Paleo] and [https://www.pangaea.de/ Pangaea].

== Voting ==
The wiki keeps a tally of votes on any poll. To ensure accurate counts, you must be a member to vote. If you are not already, please use [http://linked.earth/?wpgform_qv=1002 the membership form] to get an account.
Many polls are currently active.
<poll>
STATS
</poll>

For more details, see [[PollingStats|Advanced Statistics]]

= Standard Publication =
Once the community has spoken on these matters, the decisions will be summarized in a publication.

A formal standard is a specification of some practice that is adopted by a recognized standards body. The set of formal standards and set of de facto standards intersect, but are not the same; some formal standards are not very widely used. Nonetheless, because of the community participation and rigor required to formalize the standard we recognize that they merit careful evaluation. [http://www.earthcube.org/document/2015/ecstandardsrecs]

In the internet age, a standard can be a web-based document that details all the specifications pertaining to a technical matter. To encourage community participation and promote transparency, the LinkedEarth team will lead a '''crowd-sourced peer-reviewed publication''' detailing this standard.

==Platform==
The writing process will take place in the collaborative platform [https://www.authorea.com Authorea] and synthesize the decisions taken, and the pertinent discussions that led to such decisions.

==Authorship==
Pursuant to PAGES policies, authorship will be extremely inclusive and acknowledge all scientific input into the process. Anyone contributing to the discussion on developing standards for paleoclimatology (either during the [[PDS workshop 2016]], on the wiki, or via teleconferences an in-person exchanges) will be invited to the author list.

Authorship will be consortium-based (provisional name: "Working Group on Paleo Data Standards")

Talk:LiPD Utilities

2017-07-04T13:11:41Z

Jeg: /* -- ~~~~ */ new section

== -- [[User:Jeg|JEG]] ([[User talk:Jeg|talk]]) 06:11, 4 July 2017 (PDT) ==

This page gives the dangerously misleading impression that the LiPD utilities only exist in Python - this will turn off a large number of users.

It's critical to explain that there are core utilities in Python, R and Matlab. Can Chris do that?

Main Page

2017-06-27T18:40:08Z

Jeg:

[[File:EarthLinked_Banner_blue_NoShadow.jpg|center|440px|alt=LinkedEarthLogo]]

<div style = "text-align:center;">Welcome to the LinkedEarth Wiki!</div>

The LinkedEarth wiki is a platform that:
#enables the curation of publicly-accessible database by paleoclimate experts, and
#fosters the development of standards, so paleoclimate data are easier to analyze, share, and re-use. 

==Getting started with LinkedEarth==

<gallery mode = "packed-overlay" widths=150px heights=100px>
File:JoinUsIcon MainPage.png | [http://linked.earth/aboutus/membership/ Join LinkedEarth]
File:GettingStartedIcon MainPage.png | [[Get_Started_with_the_LinkedEarth_wiki | StartUp Guide]]
File:Browse The Wiki.png | [[Special:random | Browse existing pages]]
</gallery>

Several tutorials are also available on our [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel]!

==Community Activities==

Join a [[:Category:Working Group | working group]] (WG) and participate in the discussion about [[Paleoclimate_Data_Standards | paleoclimate data standards]].

'''New''': Each working group has polls waiting for community input. ''You must be logged in to vote.''

In the Linked Earth context, a WG is a self-organized coalition of knowledgeable experts who elaborate and discuss the components of a [[Paleoclimate_Data_Standards | data standard]] for their topic(s) of interest. WGs may be created by any member of the LinkedEarth community. Currently, the LinkedEarth community is organized around {{PAGESINCATEGORY:Working Group}} working groups.

'''To join a WG, do so on your LinkedEarth wiki profile page'''.

<gallery mode = "packed-overlay" widths=150px heights=150px>
File:Open_data_standards_trim.png | [[Paleoclimate Data Standards]]
File:WorkingGroups MainPage Icons.png | [[:Category:Working Group | Join a Working Group]]
File:Ontology_wordcloud.png | [[LinkedEarth Ontology]]
</gallery>

== Contribute Datasets ==

We recommend using the [[Linked Paleo Data | LiPD]] format to get your data on the wiki. The Python [[LiPD Utilities]] allow to create a LiPD from an Excel template, wich can be downloaded [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx here]. For instructions on filling out this template, see the page "[[Creating a LiPD file]]".

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[Creating a LiPD file]]
File:ExcelLogo.png | [http://wiki.linked.earth/File:LiPDv1.2_template.xlsx LiPD Template]
File:AnnotateDatasetImage.png | [[Dataset Tutorial | Upload a LiPD dataset]]
File:BrowseIcon.png| [[MD982181.Khider.2014 | Browse a dataset]]
</gallery>

== Working with LiPD Datasets ==

{{See also|Using LiPD files}}

The [[LiPD Utilities]], available in R, Python, and Matlab allows to read/write LiPD files, extract and collapse timeseries objects, and filter datasets according to your search criteria. Data analysis packages are currently available in R ([[GeoChronR]]) and Python ([[Pyleoclim]]). A large body of [https://github.com/CommonClimate/PAGES2k_phase2 Matlab code exists already] to analyze the [[PAGES2k]] dataset.

<gallery mode = "packed-overlay" widths=100px heights=100px>
File:LiPD Logo.jpg | [[LiPD Utilities]]
File:RLogo.jpeg | [[GeoChronR]]
File:PythonLogo.jpg | [[Pyleoclim]]
</gallery>

==Current State of the Database==

The LinkedEarth Wiki currently contains '''{{PAGESINCATEGORY:Dataset (L)}} datasets''', mostly from the [[PAGES2k]] compilation. We are in the process of adding more Holocene records, as well as >100 deep-sea cores from the LR04 benthic stack compilation. Please contact us if you want to lead a '''data drive''' to flesh it out some more.

=== Dataset Location ===



{{#ask: [[Category:Dataset_(L)]]
| ?CollectedFrom_(L).Coordinates
| ?Name_(L)
| ?ArchiveType
| markercluster=on
| showtitle=off
| zoom=1
| searchmarkers=all
| maxzoom=14
| minzoom=1
| limit=1000
| height=510
| template=LiPDLocation
| format=leaflet
}}

=== Recently Contributed Datasets ===

{{#ask: [[Category:Dataset (L)]]
| ?CollectedFrom (L).CoordinatesFor=LiPD Dataset
| ?ArchiveType
| ?CollectedFrom (L).Coordinates
| mainlabel=-
| limit=10
| format=broadtable
| sort=Modification date
| order = descending
}}

=== Search the Database by Archive===



<gallery mode = "packed-overlay" widths=200px heights=200px>
File:Coral_Archive_200px.jpg | [[:Category:Coral | Coral]]
File:Documents_Archive_200px.jpg | [[:Category:Document | Document]]
File:GlacierIce_Archive_200px.jpg | [[:Category:GlacierIce | Glacier Ice]]
File:Lake_Archive_200px.jpg | [[:Category:LakeSediment | Lake Sediment]]
File:MarineSediment_Archive_200px.jpg | [[:Category:MarineSediment | Marine Sediment]]
File:Mollusk_Archive_200px.jpg | [[:Category:MolluskShells | Mollusk Shells]]
File:Peat_Archive_200px.jpg | [[:Category:Peat | Peat]]
File:Sclerosponge_Archive_200px.jpg | [[:Category:Sclerosponge | Sclerosponge]]
File:Speleothem_Archive_200px.jpg | [[:Category:Speleothem | Speleothem]]
File:Wood_Archive_200px.jpg | [[:Category:Wood | Wood]]
</gallery>

== More about LinkedEarth ==

Website: [http://linked.earth LinkedEarth Website]

Social Media: [https://www.facebook.com/LinkedEarth-1018909201501056/?fref=ts Facebook] | [https://twitter.com/Linked_Earth Twitter] | [https://www.youtube.com/channel/UCo7yzNTM__4g5H-xyWV5KbA YouTube channel] | [https://github.com/LinkedEarth GitHub]

J. Emile-Geay

2017-06-27T04:26:00Z

Jeg: added country

[[Category:Person_(L)]]
__NOCACHE__
{{#set:
Country=France, USA|
Current Affiliation=University of Southern California|
Current Position=Associate Professor|
Email (L)=julieneg@usc.edu|
Expertise=Climate_Dynamics|
Expertise=Paleoclimatology|
Expertise=Geoinformatics|
Expertise=Statistics|
Github ID=CommonClimate|
Google Scholar ID=http://scholar.google.com/citations?user=OVti4jEAAAAJ&hl=en|
Has User ID=Jeg|
Highest Degree=PhD|
Leadership Roles=LinkedEarth PI, PAGES data stewarship|
Name (L)=J. Emile-Geay|
Name (L)=Julien Emile-Geay|
OrcidNumber (L)=0000-0001-5920-4751|
Picture URL=Http://wiki.linked.earth/wiki/images/4/45/JEG_usc_greenshirt_small.jpg|
Subscribes To=Category:Ice_Cores_Working_Group|
Subscribes To=Category:Marine_Sediment_Working_Group|
Subscribes To=Category:Chronologies_Working_Group|
Subscribes To=Category:MARPA_Working_Group|
Subscribes To=Category:Speleothem_Working_Group|
Twitter ID=@el_nino_waves|
University=Columbia University|
Website=http://climdyn.usc.edu/}}

Talk:Weekly Summary

2017-06-27T01:20:31Z

Jeg:

== -- [[User:Jeg|JEG]] ([[User talk:Jeg|talk]]) 13:42, 26 June 2017 (PDT) ==

Nice page! I think we can eliminate the "More other links" and "More updated working group links" sections.

Maybe call this a weekly digest?

===Re: -- [[User:Admin|Admin]] ([[User talk:Admin|talk]]) 14:29, 26 June 2017 (PDT)===

Yes, weekly digest makes sense. The "more other links" will have pointers to other datasets/authors that have been contributing as well. I think they are valuable, but we will try to simplify them

====Re: Re: -- [[User:Jeg|JEG]] ([[User talk:Jeg|talk]]) 18:20, 26 June 2017 (PDT)====

:: Sounds good - right now they needlessly clutter the page. The shorter the digest, the more likely it is to be read.

Talk:Weekly Summary

2017-06-26T20:42:52Z

Jeg: /* -- ~~~~ */ new section

Talk:PYTE66BFL9X.gdgt

2017-06-22T04:58:01Z

Jeg: /* -- ~~~~ */ new section

== -- [[User:Jeg|JEG]] ([[User talk:Jeg|talk]]) 21:58, 21 June 2017 (PDT) ==

This looks like a typo: should CDGT be GDGT?

Property:CompilationChangeLog (L)

2017-06-20T23:32:31Z

Jeg: Created page with "A page or literal describing changes since the last version of said compilation"

A page or literal describing changes since the last version of said compilation

Main Page

2017-06-20T18:04:57Z

Jeg: /* Current State of the Database */

D18O

2017-06-12T18:00:51Z

Jeg: changed notation to delta

=== δ18O ===

Oxygen has three naturally-occuring stable [[:Category:Isotope | isotopes]]: 16O, 17O, 18O, with 16O being the most abundant (99.762%).

Two international reference [[standard | standards]] are used to report variations in oxygen isotope standards: [[PDB]] and [[SMOW]]. The use of the [[PDB]] standard in reporting oxygen isotope composition is restricted to carbonates of low-temperature origins (e.g., [[Marine sediment | oceanic]], [[Lake sediment | lacustrine ]]). The conversion between SMOW and PDB scales is given by:

<div style="text-align: center;"> <math> \delta^{18}O_{SMOW} = 1.03091 (\delta^{18}O_{PDB}) +30.91 </math> </div>

δ18O may be measured on:
*the [[stable oxygen isotopes in foraminifera | shells]] of [[:Category:Foraminifera | foraminifera]]


[[Category:StableOxygenIsotope]]

DSDP607.Lisiecki.2005

2017-06-12T17:57:45Z

Jeg: Added PropertyValue: DatasetVersion (L) = 0.0.0

[[Category:Dataset_(L)]]{{#set:
ArchiveType=marine sediment|
CollectedFrom (L)=DSDP607.Lisiecki.2005.Location|
Contributor (L)=L.E._Lisiecki|
Contributor (L)=M.E._Raymo|
DatasetVersion (L)=0.0.0|
IncludesPaleoData (L)=DSDP607.Lisiecki.2005.PaleoData1|
LiPDVersion=1.2|
Name (L)=DSDP607.Lisiecki.2005|
PartOfCompilation (L)=LR04_benthic_stack|
PublishedIn (L)=Publication.10.1029/2004PA001071|
PublishedIn (L)=Publication.DSDP607.Lisiecki.2005}}