Aim:The International Tree-Ring Data Bank (ITRDB) is the most comprehensive database of tree growth. To evaluate its usefulness and improve its accessibility to the broad scientific community, we aimed to: (a) quantify its biases, (b) assess how well it represents global forests, (c) develop tools to identify priority areas to improve its representativity, and d) make available the corrected database.Location: Worldwide. Time period: Contributed datasets between 1974 and 2017.Major taxa studied: Trees. Methods:We identified and corrected formatting issues in all individual datasets of the ITRDB. We then calculated the representativity of the ITRDB with respect to species, spatial coverage, climatic regions, elevations, need for data update, climatic limitations on growth, vascular plant diversity, and associated animal diversity. We combined these metrics into a global Priority Sampling Index (PSI) to highlight ways to improve ITRDB representativity. Results:Our refined dataset provides access to a network of >52 million growth data points worldwide. We found, however, that the database is dominated by trees from forests with low diversity, in semi-arid climates, coniferous species, and in western North America. Conifers represented 81% of the ITRDB and even in wellsampled areas, broadleaves were poorly represented. Our PSI stressed the need to increase the database diversity in terms of broadleaf species and identified poorly represented regions that require scientific attention. Great gains will be made by increasing research and data sharing in African, Asian, and South American forests. Main conclusions:The extensive data and coverage of the ITRDB show great promise to address macroecological questions. To achieve this, however, we have to overcome the significant gaps in the representativity of the ITRDB. A strategic and organized group effort is required, and we hope the tools and data provided here can guide the efforts to improve this invaluable database. K E Y W O R D Sbias analysis, big data, data accessibility, Dendrochronology, dendroecology, meta-analysis, tree growth, tree-ring research

The Paleoclimate Modelling Intercomparison Project (PMIP3) now includes the 8.2 ka event as a test of model sensitivity to North Atlantic freshwater forcing. To provide benchmarks for intercomparison, we compiled and analyzed high-resolution records spanning this event. Two previously-described anomaly patterns that emerge are cooling around the North Atlantic and drier conditions in the Northern Hemisphere tropics. Newer to this compilation are more robustly-defined wetter conditions in the Southern Hemisphere tropics and regionally-limited warming in the Southern Hemisphere. Most anomalies around the globe lasted on the order of 100 to 150 yr. More quantitative reconstructions are now available and indicate cooling of ~ 1 °C and a ~ 20% decrease in precipitation in parts of Europe as well as spatial gradients in δ¹⁸O from the high to low latitudes. Unresolved questions remain about the seasonality of the climate response to freshwater forcing and the extent to which the bipolar seesaw operated in the early Holocene

[1] High-resolution temperature reconstructions (typically annually to seasonally resolved) have played a key role in understanding paleoclimate immediately prior to the beginning of the instrumental record, especially when calibrated to form an extension of comparable instrumental data coverage (global, hemispheric, and regional). Such calibration allows the information in the instrumental record to be quantitatively extended backward in time in an objective way, enabling description of much longer term fluctuations in climate than possible with instrumental data alone, although with significantly increased uncertainties inherent in proxy-based reconstructions. This data brief describes a newly integrated archive of nearly all the high-resolution temperature reconstructions of the past 2+ millennia included in NOAA's National Climatic Data Center, from small-regional to global scale, which also have been recalibrated to a standard set of instrumental data. Examination of the spectral structure of the data is additionally provided.

This synthesis of thirty-six sites (sixty cores with over 27 000 measurements) located around the world facilitates scientific research on the climate of the last 21 000 years ago obtained from oxygen isotope (í µí»¿ 18 O or delta-O-18) measurements. Oxygen isotopes in speleothem calcite record the influence of ambient temperature and the isotopic composition of the source water, the latter providing evidence of hydrologic variability and change. Compared to paleoclimate proxies from sedimentary archives, the age uncertainty is unusually small, around +/−100 years for the last 21 000-year interval. Using data contributed to the World Data Center (WDC) for Paleoclimatology, we have created consistently formatted data files for individual sites as well as composite dataset of annual to millennial resolution. These individual files also contain the chronology information about the sites. The data are useful in understanding hydrologic variability at local and regional scales, such as the Asian summer monsoon and the Intertropical Convergence Zone (as discussed in the underlying source publications), and should also be useful in understanding large-scale aspects of hydrologic change since the Last Glacial Maximum (LGM).

The Paleoclimate Modelling Intercomparison Project (PMIP3) now includes the 8.2 ka event as a test of model sensitivity to North Atlantic freshwater forcing. To provide benchmarks for intercomparison, we compiled and analyzed high-resolution records spanning this event. Two previously-described anomaly patterns that emerge are cooling around the North Atlantic and drier conditions in the Northern Hemisphere tropics. Newer to this compilation are more robustly-defined wetter conditions in the Southern Hemisphere tropics and regionally-limited warming in the Southern Hemisphere. Most anomalies around the globe lasted on the order of 100 to 150 yr. More quantitative reconstructions are now available and indicate cooling of 1.0 to 1.2 °C and a ~20% decrease in precipitation in parts of Europe, as well as spatial gradients in δ¹⁸O from the high to low latitudes. Unresolved questions remain about the seasonality of the climate response to freshwater forcing and the extent to which the bipolar seesaw operated in the early Holocene

Paleoscience data are extremely heterogeneous; hundreds of different types of measurements and reconstructions are routinely made by scientists on a variety of types of physical samples. This heterogeneity is one of the biggest barriers to finding paleoclimatic records, to building large‐scale data products, and to the use of paleoscience data beyond the community of specialists. Here, we document the Paleoenvironmental Standard Terms (PaST) thesaurus, the first authoritative vocabulary of standardized variable names for paleoclimatic and paleoenvironmental data developed in a formal knowledge organization structure. This structure is designed to improve data set discovery, support automated processing of data, and provide connectivity to other vocabularies. PaST is now used operationally at the World Data Service for Paleoclimatology (WDS‐Paleo), one of the largest repositories of paleoscience information. Terms from the PaST thesaurus standardize a broad array of paleoenvironmental and paleoclimatic measured and inferred variables, providing enough detail for accurate and precise data discovery and thereby promoting data reuse. We describe the main design decisions and features of the thesaurus, the governance structure for ongoing maintenance, and WDS‐Paleo services that now employ PaST. These services include an advanced search by variable name, an interface for thesaurus navigation, and a machine‐readable representation in the Simple Knowledge Organization System (SKOS) standard. This overview is designed for developers of thesauri, data contributors, and users of the WDS‐Paleo, and serves as a building block for future efforts within the broader paleoscience community to improve how data are described for long‐term findability, accessibility, interoperability, and reusability.

Reducing uncertainty in global temperature reconstructions of the past millennium remains the key issue in applying this record to society's pressing climate change problem. Reconstructions are collaborative, built on the research of hundreds of scientists who apply their diverse scientific expertise and field and laboratory skill to create the individual proxy reconstructions that underlie the multi-proxy, global average temperature time series. Web 2.0 features have enabled collaborative efforts that improve the characterization of uncertainty. Raw data shared via a repository (the World Data Center for Paleoclimatology) enable new reconstructions from the collection of usergenerated data. Standards propagated by expert communities facilitate quality control and interoperability. Open access to data and computer code promote transparency and make the science accessible to a broader audience. Blogs, wikis, and listservs share background information and highlight contentious as well as unique aspects of paleo science. A novel approach now underway, titled the Paleoclimate Reconstruction Challenge, and based on the sharing of simulated data (pseudo-proxies) and reconstruction results, seeks to facilitate method development, further reducing uncertainty. Broadly-useful aspects of the Challenge may find application in other fields.

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