Trans-regional projects (Phase 2)
PAGES 2k Network trans-regional projects originated from 2k Network members and addressed research questions that involved more than one 2k region. These projects complemented the work of the former regional groups and took advantage of expertise and data compilations being generated as a result of the global 2k Network.
A first goal of this project was the comparison of the PAGES 2k continental-scale temperature reconstructions with the multi-model simulations of the past millennium, blending the PAGES 2k and PMIP3 communities. The comparative analyses emphasized climate change at regional scales and an understanding of the mechanisms of climate change at decadal to centennial timescales. Read the outcome "Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium", published in Climate of the Past, here.
Contact: Hugues Goosse (PMIP Liaison & 2k co-coordinator)
This project was devoted to the comparison of the hydroclimate reconstructions with the multi-model simulations of the past millennium, blending the PAGES 2k proxy communities and PMIP3 modeling communities. The comparative analyses emphasized the methods appropriate for data-model comparisons that target hydroclimate in order to understand climate change at regional scales and the mechanisms of climate variability at decadal to centennial timescales. Read the outcome "Comparing proxy and model estimates of hydroclimate variability and change over the Common Era", published in Climate of the Past, here.
Contact: Jason Smerdon
2k Database projects
Global 2k Paleotemperatures Dataset v2 - Data Descriptor
The "data descriptor" for version 2 of the 2k paleotemperature database accompanied the publication of the dataset. This new type of peer-reviewed data-oriented publication was designed to promote greater understanding, accessibility and reuse of datasets. The data descriptor included the selection criteria, and basic diagnostics of the dataset, including a first-pass, index reconstruction of global temperature. This provided a better global temperature reconstruction than the average of the regional reconstructions, which was published in the 2013 2k Consortium paper. Reconstructions of spatial patterns of temperature variability will be tackled in a subsequent project (see "Global Temperature Reconstruction" project, below).
Contact: Julien Emile-Geay
Water Isotope Database
Stable water isotopes detect regional-scale circulation patterns, making them excellent tracers of the water cycle's response to climate change. This Trans-Regional Project will create a global database of stable oxygen and hydrogen isotope records that researchers can use to assess regional- and global-scale changes in rainfall and atmospheric/oceanic circulation patterns during the past 2,000 years.
Reconstructions based on the PAGES 2k Temperature Database
Global gridded temperature reconstruction method comparisons
This project will produce global gridded temperature reconstructions using a suite of climate field reconstruction (CFR) methods applied to the new PAGES 2k temperature database. The aim is to assess how the results of the various methods agree and disagree (such as low-frequency amplitudes vs. decadal-scale fluctuations, timing of extremes, spectral slopes, spatio-temporal distribution of skill and uncertainties), to better constrain what type of analysis CRF products are best suitable for. If you are interested to contribute please write to the contact address.
Global mean temperature (index) reconstruction
This collaborative group effort aims to use the PAGES 2k temperature proxy database to produce reconstructions of global mean surface temperature (GMST) over the past 2000 years. A range of state-of-the-art reconstruction techniques will be applied in coordinated reconstruction experiments to maximise comparability across the results. The index reconstructions will be used to identify and quantify features of global mean temperature change that stand up to a wide range of reconstruction choices and approaches.
Onset of industrial warming in terrestrial and marine records
This PAGES 2k Consortium project used the regional temperature reconstructions and databases produced by the PAGES 2k working groups to assess the onset of sustained, significant warming during the Industrial Era across the oceans and continents. The statistical methods for assessing the onset of warming were developed and tested, and the MATLAB code was archived. The study found that sustained industrial-era warming began in the mid 19th Century over Northern Hemisphere landmasses and in the tropical oceans, and that this early onset of warming was consistent with CMIP5/PMIP3 Last Millennium simulations run with full forcing or with greenhouse gas forcing only. In the Southern Hemisphere, the onset of warming was delayed in the PAGES 2k reconstructions, but this delay is not evident in current climate model simulations. The study "Early onset of industrial-era warming across the oceans and continents" was published in Nature, and the data archive associated with the paper is available through the NOAA's National Centers for Environmental Information.
Contact: Nerilie J. Abram
AMOC and atmospheric circulation pattern estimations
Marine paleoclimate data described in the Ocean2K paleodata metadatabase will be combined with CMIP5 simulations to reconstruct ocean circulation patterns using the proxy surrogate reconstruction algorithm. We will also evaluate the precision and uncertainty of the results, and use pseudoproxy experiments to identify regions for which additional data might most improve the results.
Contact: Casey Saenger
Temperature index reconstructions were created for seven continental-scale 2k regions. All regional groups used the set of data and methods deemed most appropriate in their region. In addition, to assess the influence of the various reconstruction methods, all regional reconstructions were also calculated using a common set of methods. This study showed that the most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age. And, that the twentieth century ranked as the warmest or nearly the warmest century in all regions except Antarctica More details to this study here.
Contact: Darrell Kaufman
This study used proxy temperature records from the Australasian, South American, African, and Antarctic PAGES 2k working groups to create a new Southern Hemisphere temperature reconstruction for the last 1000 years. This reconstruction was then compared to the Northern Hemisphere ensemble temperature reconstruction by Frank et al. (2010) and climate model simulations. The results (Neukom et al. 2014) indicate distinct differences in temperature fluctuations between the two hemispheres over large parts of the last Millennium. Model simulations appear to underestimate these inter-hemispheric differences and the role of internal ocean–atmosphere dynamics, particularly in the ocean-dominated Southern Hemisphere.
Contact: Raphael Neukom
Over more than two years (2011-2013), the regional 2k data managers worked closely with the National Centers for Environmental Information at NOAA to tailor the 2K Network database infrastructure for paleoclimate data, and prepare the upload of the PAGES 2k database. In addition, they provided expertise and advice that helped promote improvements in NOAA WDC-Paleo's ingest of paleoscientific data in general. Because the data managers of the regional 2k groups are spread across the globe, the collaboration was organized around bi-monthly teleconference meetings under the lead of WDC-Paleo. Read more about the 2k-NOAA data managers meetings and their outcome here.
Contact: Eugene Wahl