Meeting 09/03/2015
Brief overview of the PAGES 2k project for newcomers
Darrell Kaufman who is leading the discussions welcomes the participants, reviews the technicalities and present a brief overview of the PAGES2K network.
The project has 9 regional working groups and is coordinated by a small group, facilitating the interactions. Each group as a leader (or group of leaders) as well as a data manager. In additional, trans-regional topics are set up to address question that covers several regions .The first phase of the project culminated in the Nature Geosciences Paper. For phase 2, most regional groups have a new leadership. A first focus is to develop an update of the temperature dataset. We need also to make progress on a hydroclimate data base and on the way to analyze regional hydroclimate changes.

Update on v2 of the temperature database and data descriptor
The goal is to build up a data product that can be used for answering a wide range of scientific questions. As a first step, the short-term objective is to have soon a data paper lead by Julien Emile-Geay for the journal Scientific Data. The project is well advanced. Collecting all the data was quite a task. A few preliminary figures are presented by Julien. The data base includes more than 1000 records. The first step of quality control has been achieved but a new round is planned in the near future. Julien presents some characteristics of the data set (number of annual records, length of the records). The interpretation relies basically on the meta-data provided. Question on some individual records will be asked to the regional groups while the analysis are performed in the coming weeks. A key point is to determine the screening criteria for a record to be included in global temperature reconstructions. Julien and Nick will post some key diagnostics for a quality control by the participants.

Strategies for completing the global 2k hydroclimate database
The idea is to have a data product for hydroclimate that is similar to the one on track for temperature (see previous point). 
For the temperature, the various steps were:
• Establish criteria for which records to include
• Set a schedule with deadlines
• Work within regional groups to compile data and channel through clearing house
• Identify a corresponding author for the PAGES 2k consortium product
• Write a “data descriptor” for Scientific Data or other data-oriented journal
• Distribute data set; encourage and coordinate use across the community
Darrell presents the suggested schedule:
• 31 May: All records that meet PAGES 2k criteria submitted to PAGES
• 30 June: Data formatted and quality-controlled by all co-authors
• 31 July: Data product submitted for publication
This schedule is driven both by PAGES2K timeline and is consistent with the one of the past millennium reanalysis project. Ensuring the quality of the data is time consuming and some participants wonder if the proposed hydroclimate database time frame is too compressed. Nevertheless, the timing appears straight but reasonable given the constraints and so can be considered as the target for the group. We could at least have the objective to have parts of the data (for instance isotopes, see below) while some others are coming later for new versions of the data base. 
A suggestion is to focus on one or a few variables first (in particular isotope records because it’s well defined and do-able within a short time frame, isotope is a key source of hydroclimate information, It’s timely and of broad interest, along with the development of isotope-enabled GCMs)
However, no type of record is excluded a priori. Short records are also useful, so including them may be considered interesting, in particular for some regions like Australasia and South America where there is not that much long records. Some flexibility should thus be maintained to ensure that all groups can take part efficiently in the synthesis. The data base should be used for different purposes so it is better to be more general: long and short records should be included so that everyone can select the data needed. Isotopes (and other hydroclimate proxies) are not easy to interpret; meta-data are thus be very useful as well as isotope-enabled GCMs. Many records are not pure temperature or hydroclimate, but we should keep those records too in the data base.
Brownen Konecky has proposed to lead or co-lead the effort on the isotope synthesis. The suggestion that (regional) groups for which isotopes is not the best source of hydrological information propose other variables or criteria that are best suited for their regions. Additionally, different target variables (precipitation, moisture availability, surface salinity) may be more adapted to represent hydroclimate changes in different regions. The varve group is setting up a database that can be mined for hydroclimate. There is thus a lot of potential synergy. The regional groups (or regional data bases) are also a good place to help in the interpretation of the records.

Approaches to analyzing regional hydroclimate changes
North America: Not planning to have gridded moisture or precipitation because of the already available information. A target is to have a synthesis of water isotopes. In a next step, it is planned to use other records of hydroclimate, focusing on a few key periods.
Australasia: There is a focused on some single proxy records of hydroclimate variations. Additionally, attempts are currently made to have multiple proxy reconstruction of PDSI. Shift from temperature to hydroclimate takes some time to set up.
Arctic: Analyzing different records (from glacier, ice core, tree rings, etc) of hydroclimate in parallel to other activities (improving dating, evaluating the quality of records, index reconstructions)
Ocean: Ocean2K have discussed hydroclimate as part of phase 2 – in the process of defining projects and champions for those projects. From the marine perspective however, there is the key question of whether hydroclimate is moisture and/or rainfall. It is also planned to have moisture balance comparison with models from marine perspective – longer time and spatial (ocean basin) scales. High resolution records in the tropics can give rainfall via coral paired Sr/Ca and δ18O. In the tropics δ18O alone as a rainfall proxy may be difficult because of the tight coupling between SST and rainfall. δ18O in some regions is predominantly an SST proxy (although that could be used to infer rainfall). Other datasets may give insights. E.g. δ18O from bivalves in the extratropics. Should we aim at quantitative reconstructions only. There are some qualitative reconstructions that may be of use. From Ocean2K point of view getting the data together and quality controlled is critical. Ocean2K have some science questions but need to see if we have the data to answer those questions. From this point of view we thought realistically we would need more time for quality control and getting the data together.
Europe2K: Products are already available for hydroclimate (gridded reconstruction, European drought Atlas). The goal is to have a new gridded reconstruction based on multi-proxies and various reconstruction techniques.
Trans-regional products Nerilie Abram is working on a synthesis on ocean and terrestrial data focusing on the last centuries. Kevin Anchukatis presents the work done on reconstructions. Important issues are the combination of low resolution proxies and high resolution ones. Proxy forward models, bayesian hierarchy model and data assimilation approaches are also a focus. A synthesis of comparison of model results (CMIP5/PMIP3) and PAGES2K reconstructions at decadal scale is underway as well as a synthesis of varve data.
The last millennium reanalysis based on various forward proxy records to constrain reconstructions of past climate changes, so synergies are needed, in particular in the collection of data and meta-data (including selection criteria).

Timeline and outlet for a journal special issue
The timeline for a synthesis product of PAGES2K is 2016. A suggestion is to have a special issue for the PAGES 2k project in the open-access, transparent-review journal, “Climate of the Past”. This special issue should include both papers specific for individual groups as well as synthesis papers. The submission window would be 1 July to 31 Dec 2016.  All the comments received during the meeting are in favor of this special issue. The 2016 deadline is important for PAGES as new proposals for PAGES have to be submitted at that time and having strong products is important for the success of the proposal.