dataesr/scientific-paragraphs-categorization huggingface dataset:
, 2009). Also,  Jasechko et al. (2015)  compiled 88 isotope records from ground water, speleothems and ice cores spanning the period from the LGM to the Late Holocene and compared these data to five general circulation models. These model-data comparisons have only used limited information extracted from a fraction of available proxy records, while much broader information has been accumulated during decades of field and laboratory work worldwide. The main open-access databases are hosted on the NOAA (http://www. ncdc. noaa. gov/data-access/ paleoclimatology-data) and PANGAEA (http: //www. pangaea. de) websites. These multi-proxy online data depositories are continuously updated with recent datasets uploaded by the respective authors on a voluntary basis. In some cases, datasets are also available as supplementary information to publications, and practices depend on communities.
For instance, there is no standard practice for archiving the growing number of stable isotope records obtained from tree-ring cellulose, even though some efforts emerged recently to create a databank  (Csank, 2009). Although the two repositories have been intensively used by scientists to archive and distribute their datasets, the systematic exploration of these records remained limited by the heterogeneity of reporting, data formats including chronological information, and the impossibility of easily downloading all the datasets related to one type of proxy. Moreover, these databases have limited interactivity. The lack of features allowing an online pre-visualization of selected datasets obliges the users to download the data if they want to assess the relevance of the records for their scientific questions (e.
g. , to explore the resolution of the records, or the quality of the chronology for a given time interval). Altogether, nonintuitive ergonomics and/or limited interactivity make data browsing and gathering fastidious. Based on this observation, we decided to produce a compilation of existing records, standardizing the chronological information (age markers) into a common format and implementing an online tool to facilitate the search process throughout different archives with intuitive data browsing, online functions for graphical pre-visualization of datasets, and easy download features. In a first step, we focus here on δ 18 O, δD and, if available on the same archive, δ 17 O and δ 13 C. This choice is motivated by the following reasons: (i) these proxies have been widely used during the last decades; (ii) they are available for a variety of marine, ice and terrestrial archives (sediments, speleothems, ice and tree-ring cellulose); and (iii) they trace interactions between different components of the climate system involved in the global water and carbon cycles, and provide therefore integrated signals for evaluating respectively water and carbon cycle processes within climate simulations.
A strong motivation for this compilation is the integration of marine and terrestrial records  (Bar-Matthews et al. , 2003; Hughen et al. , 2006; Cruz et al. , 2006; Leduc et al. , 2009; Carré et al. , 2012; Bard et al. , 2013; Grant et al. , 2012 Grant et al. , , 2014)). It is also in line with ongoing efforts to build consistent chronologies for marine and ice core records (e. g. , the INTIMATE project; see  Blockley et al. , 2012). In order to document the four-dimensional structure of ocean circulation changes, we included datasets from deep-sea sediments, using both surface-and deep-water proxies. While in principle our methodology could allow one to explore transient climatic changes  (Marcott et al. , 2013; Shakun et al. , 2012) , such an approach would require an accurate assessment of age-scale uncertainties, which is beyond the scope of this work.
In this manuscript, we therefore focus on records providing sufficient age control and resolution for selected time slices, chosen for consistency with the Paleoclimate Modelling Intercomparison Project (PMIP), and for which numerous source records are available. The selection of target periods is described in Sect. 2. The protocols and methods used to build the database are then depicted in Sect. 3, followed by the description of the software developments required for the online search and visualization platform (Sect. 4). For the four considered time slices, we then illustrate the data coverage and spatial distributions (Sect. 5). Our conclusions provide recommendations to facilitate such data syntheses and propose future database developments.
Selection of target periods Although the database contains full-length published records, allowing the investigation of transient climatic changes, our data synthesis in the frame of this manuscript is focused on key periods for which there is a specific interest in the paleoclimate modeling community: the last 200 years, the mid-Holocene (MH), the Last Glacial Maximum (LGM) and the last interglacial period (hereafter LIG). The methodology used to estimate the isotopic offset between the different periods and the determination of its significance is provided in the Appendix. The last 214 years (1800 to 2013 CE, Common Era, noted as "last 200 years" for simplification) have been selected because (i) they encompass instrumental measurements (precipitation or seawater isotopic composition, air and water temperature, rainfall, sea level pressure) and because (ii) isotopic atmospheric models can be nudged towards atmospheric historical reanalyses, thus providing a realistic framework for model-data comparisons (e.
g. ,  Yoshimura et al. , 2008). It is here in fact extended back to 1800 to encompass, if possible, the climate response to the large 1809 and 1815 volcanic eruptions. This period is particularly important for detection and attribution of climate change, and, so far, the short duration of isotopic measurements in precipitation samples (i. e. , at best 60 years for δ 18 O in central Europe;  Araguas-Araguas et al. , 2000; GNIP Database, IAEA/WMO, 2015)  has limited systematic investigation of recent trends. Here, we aim at expanding this documentation from highly resolved proxy archives (mostly ice cores and tree-ring cellulose). Note that the records do not necessarily span the entire key periods (i. e. , a record spanning only the last 50 years would be included in our statistics for the present-day period).
, 2013; Rohling et al. , 2012; Schmidt et al. , 2014)  natural archives with improved chronologies  (Reimer et al. , 2013). A synthesis of marine data has been achieved within the MARGO collaborative effort  (Waelbroeck et al. , 2009) , leading to a database of multi-proxy sea surface temperature estimates, complementing surface air temperature change between the LGM and present day inferred from pollen and ice core records  (Braconnot et al. , 2012). This period is marked by changes in the thermohaline circulation  (Duplessy et al. , 1988; Shin et al. , 2003; Yu et al. , 1996) , large scale atmospheric circulation  (Chylek et al. , 2001; Justino and Peltier, 2005, Murakami et al. , 2008) , El Niño-Southern Oscillation (ENSO;  Tudhope et al. , 2001; Stott et al. , 2002)  as well as the monsoon and Intertropical Convergence Zone (ITCZ) position  (Van Campo, 1986; Braconnot et al.
Database construction steps The first step consisted in gathering all the δ 18 O, δ 13 C and δD data available from the two main online paleoclimate data depositories (NOAA and PANGAEA), together with marine sediment records from the LSCE (Gif-sur-Yvette, France), paleoceanography internal database  (Caley et al. , 2014)  and literature survey and personal communication  (2013, 2014)  with authors. This work was performed from May 2013 to July 2014. A metafile has been built in order to list the main parameters of these datasets: core name; reference; associated publication digital object identifier (DOI); and core site latitude, longitude and elevation or depth coordinates. We have also inserted a flag to describe the quality of age models for marine sediment cores (see next section). All ages were converted into kiloyears before present (ka), using 1950 CE as the reference year.
Although arbitrarily dated, these data points were integrated to the calculation of present-day average values. 6. For records older than the 14 C reliability interval (∼ 35 to 60 ka, where the uncertainty on the calibration into calendar ages strongly increases;  Plastino and Bella, 2001; Bronk-Ramsey et al. , 2013) , the quality flags are based on the number of tie points and the type of material used for core-to-core correlation (e. g. , welldated, high-resolution ice core vs. low-resolution sediment core). Quality flags ranging from 1 (very good) to 5 (poor) were therefore included in the metafile for each deep-sea sediment core and speleothem dataset. This evaluation protocol was not applied to archives such as tree rings, varved lacustrine cores, high-accumulation ice cores, modern corals or mollusk shells where annual counting allows for building accurate chronologies.
Ice cores Dating ice cores is a crucial issue, as these highly resolved archives are often compared to marine cores and speleothems to assess the timing of climatic events between high and lower latitudes. Ice core chronologies are regularly updated using available age markers and dating is synchronized among different ice cores (e. g. ,  Rasmussen et al. , 2006; Vinther et al. , 2006; Ruth et al. , 2007; Bazin et al. , 2013; Veres et al. , 2013) , with estimates of associated age-scale uncertainties. For that reason, it was decided not to attribute dating quality flags for ice cores chronologies in this database. For the last interglacial period, LGM and MH, most ice cores chronologies would be flagged as good to excellent, depending on the dating strategy. For the last 200 years, the quality of ice core chronologies can vary from excellent for high accumulation areas (where annual layer counting and volcanic horizons are available) to good in the driest central Antarctic areas.
Lacustrine records The construction of age models for lacustrine cores is somewhat similar to what is applied for marine cores. Most of the chronologies are based on AMS 14 C dating measured on carbonate or organic compounds. Similarly to what was performed for marine datasets, the quality flags for lacustrine records are based on the density of 14 C dates and their position relatively to key transitions. We also took the sedimentary disturbances (e. g. , sedimentation hiatuses) into account as well as the presence of potential corrections for residence time and reservoir effects revealing an effort for considering the impact of the lake circulation dynamics in the sediment age. The chronology of some of the compiled lacustrine records was performed by counting of seasonal varve, generally resulting in a high accuracy  (Sprowl, 1993).
Interactive visualization tool NOAA and PANGEA open-access online libraries host a huge amount of paleoclimatic datasets, but browsing and downloading these data may sometimes not be optimal. Each dataset must indeed be downloaded individually, without having the possibility to quickly visualize the records online. This is particularly critical when users need to download a large amount of records not corresponding to a specific site and/or author. This led us to develop a tool that optimizes the datasets browsing step, with an online data plotting function and a user-friendly tool for downloading multiple datasets. One of the main objectives of this application (http:// climateproxiesfinder. ipsl. fr/) is to ease exploration of multidimensional data assembled from multiple proxy records containing common features.
This approach is relatively new and benefits from the latest interactive data visualiza-  ocean, speleothem, tree) and material (e. g. , carbonate, coral, etc. ). A table of the available records is also displayed at the bottom of the screen (first 100 only). This table displays information about the records (depth, age (most recent, oldest), archive, material, DOI, and the reference of the corresponding scientific paper). The DOI is hyper-linked to the Google Scholar search engine. The user can interactively filter the dataset by clicking or brushing over any of these charts or by dragging and zooming in and out of the map. Since all charts are interconnected, they will automatically be updated according to the filter selections. Figure  1b  shows an example of this interactive filtering with the selection of ocean archive type near the surface (0-500 m).
Accordingly, due to the cross-filtering functionality, all other charts and the table reflect only the proxies selected by these filters. This application also allows the user to display an interactive plot of the time series of the available isotopes by clicking on a map marker (see Fig. 1c  for an illustration). Lastly, the user is able to download, in a zip file, the selected proxy data as CSV files and time-series plots by clicking on the shopping cart icon. The Climate Proxies Finder application continues to evolve as new features are needed, such as adding a filter for proxy chronological information quality.
Geographical distribution of data and temporal resolution This section briefly describes the status of the database for marine and terrestrial records (Fig. 3 ) and provides a synthesis of stable isotope data for each focus period. A total of ∼ 6400 records were collected from the NOAA and PANGAEA data repositories as well as from the internal LSCE database. About 3300 marine records were rejected, as they are not yet published. Following the settings of our online portal, we also isolated about 300 δ 18 O and δ 13 C published records not dated (∼ 200 records) or containing no information about the core site elevation or depth (∼ 100 records). We thus accumulated about 1700 δ 18 O records from ∼ 900 sites, about 900 δ 13 C records from 450 sites, and about 230 δD records from 60 core sites (with 20 additional deuterium excess records).
When considering the different types of archives, we compiled about 1200 δ 18 O and ∼ 700 δ 13 C records from 600 marine sediment cores, 200 δ 18 O and 75 δ 13 C speleothems records from 60 caves, 200 dated δ 18 O records from 50 ice cores (with about 60 additional dated δD datasets and ∼ 20 δ 17 O records), 60 δ 18 O and 60 δ 13 C lacustrine records (with δD datasets), and 85 δ 18 O and 80 δ 13 C records from tree rings. Among all the 1900 collected marine records, about 850 do not present any information about the construction of their age model and about 950 records are associated with age model tie points or by default associated with an excellent chronology (e. g. , modern corals), while most of the lacustrine cores and speleothems are associated to chronological information. We also note that, when not considering treering records, about 500 dated records do not present any sampling depth or distance scale.
, 1999; Ahagon et al. , 2003; Max et al. , 2014)  and storage of carbon in the Southern Ocean  (Skinner et al. , 2010; Burke and Robinson, 2011). Vast areas remain virtually undocumented in the Indian, Pacific and Southern oceans. A large majority (about 90 %) of the records of the ocean database are based on foraminifera, while corals are much scarcer and only a few studies use mollusks or diatoms. The distribution of continental records (Fig. 3 ) naturally depends on the position of caves, lakes, forests, and ice sheets and glaciers. Speleothem δ 18 O records are found on each continent, but with a very heterogeneous distribution. In fact, due to the distribution of caves presenting exploitable speleothems, several large areas (Russia and central Asia, northern and tropical Africa, Canada, central South America) remain undocumented, while the density of records is large in Europe, USA, Central America and China.
While they have provided highly resolved records of regional climate variability (e. g. , the monsoon and ITCZ, circum-Mediterranean continental climate), speleothems do not provide a global coverage. Lacustrine records are also very unevenly distributed, with very few dated isotopic records in South America, Africa, Russia and Australia, although these regions present numerous lakes. Oxygen and carbon stable isotopes from tree-ring cellulose have recently emerged as powerful paleoclimate proxies, albeit with heavy sample preparation  (Libby and Pandolfi, 1976; Long, 1982; Ehleringer and Vogel, 1993; Switsur and Waterhouse, 1998). This feature, and the fact that few tree-ring isotope datasets are available online, leads to relatively scarce archives at a global scale. imanjaro and the high-latitude Canadian islands, close to Greenland (Fig.
Speleothems Ice cores LGM-MH � 18 O difference (‰) Fraction of the total records (%) vidual short datasets separated, following the way their authors published them, and we did not build long and continuous composite records. Therefore, composite records cannot be displayed in our LIG-MH comparison map (Fig. 9 ). MH, ∼ 40 for the LGM, and 14 concerning the LIG (13, 13 and 6 for δD, respectively). Only five δ 18 O records are continuous from the LIG to the Holocene. Ice core records, however, provide a wealth of information on the spatial and temporal variability of surface snow isotopic composition over the last decades, as about 140 of the ∼ 180 compiled δ 18 O dated records spanning the last 200 years exhibit at least 10 data points within this period (50 out of 55 dated records for δD and deuterium excess).
3 2 1 0 -0. 3 -0. 6 -0. 9 -1. 2 -1. 5 -1. 8 -2. 1 -2. 4 As the effect of burial on δ 18 O of fossil wood cellulose remains poorly known  (Richter et al. , 2008) , we selected records exclusively based on living trees or timber wood. Consequently, the compiled records from tree-ring cellulose can only be used to monitor the climate fluctuations of the last millennium at the very best. We have identified ∼ 80 tree-ring cellulose δ 18 O records which cover the past 200 years (∼ 80 for δ 13 C). Most of the records have been provided at seasonal to decadal temporal resolution. Lacustrine cores are generally short and records generally span relatively limited time intervals. As a result, only the PD and MH are covered by a relatively large number of records (∼ 35 δ 18 O, 30 δ 13 C and ∼ 135 δD records for PD; 25 δ 18 O, 30 δ 13 C and ∼ 45 δD records for MH), while datasets spanning the LGM and LIG are very scarce (30 when considering δ 18 O, δ 13 C and δD records).
" These sedimentary issues are often accompanied by insufficient resolution and quality of the sediment core-tops dating procedure. In fact, present-day conditions are represented by only one data point in about half of the datasets, generally dated via linear extrapolation of deeper tie points. About 95 marine δ 18 O and 35 δ 13 C records exhibit a decadal to annual resolution, generally arising from corals (65 % of the records) with robust layer-counted annual chronology.
Datasets' temporal resolution While chronology is not an issue for tree-ring cellulose records, the number of individual tree samples combined for each year can be a limiting factor. Several studies have investigated the signal-to-noise ratio, and demonstrated the importance of combining at least 4-5 trees from a forest to extract the common climate signal (e. g. ,  McCarroll and Loader, 2004; Daux et al. , 2011; Labuhn et al. , 2014). The same issue arises for ice core records, especially for the past centuries, when the noise caused by processes such as wind scouring can be significant when compared to the small climatic signal (e. g. ,  Fisher et al. , 1985; Masson-Delmotte et al. , 2015). As a result, the records resulting from stacks combining several ice cores from a given site have stronger climatic relevance than records based on individual ice cores.
Ice core datasets encompass a large proportion (∼ 70 %; 120 records) of highly resolved (decadal to annual) records, while this percentage is significantly reduced for speleothems (about one-half of the 90 records spanning the last 200 years). For the MH and LGM, marine records also have the lowest temporal resolution, as 80 % of these datasets exhibit four data points or less over the 5. 5-6. 5 ka interval, and none of the records are available with a resolution better than respectively 20 and 40 years (Figs. A2  and A3 in Appendix A ). Ice core records spanning the MH and the LGM are relatively scarce (55 and ∼ 50 datasets, respectively), and most of them exhibit decadal to centennial resolution. Speleothem records are slightly more abundant than ice core records (90 and 55 records for the MH and the LGM, respectively), with very variable resolution, from millennial to subdecadal.
Speleothems and ice core records spanning the last interglacial are scarce (about 35 and 15 records, respectively; Fig. A4 in Appendix A ) and only some of them present a centennial resolution or better, while marine records are abundant, but most of them have millennial or lower temporal resolution. Lacustrine data can roughly be divided into two groups, with about half of the records covering only the last decades, while the other records are generally much longer, spanning Clim. Past, 12, 1693 Past, 12, -1719 Past, 12, , 2016  www. clim-past. net/12/1693/2016/ the Holocene period, and few datasets cover the glacial period. The present day is somewhat well resolved, as about 65 % of the δ 18 O and δ 13 C records spanning this time interval exhibit at least 10 data points. This trend is also observed for the MH, with about 65 % of the records presenting 10 or more data points.
Changes between MH and present day The relatively large number of dated δ 18 O datasets covering both the last 200 years (PD) and the mid-Holocene (MH) allows us to estimate possible offsets between these two periods (MH-PD; ∼ 100 records from 70 sites; Fig. 8 ). We restrict the record selection to datasets presenting multiple data points for each of the two periods of interest, thus documenting both the signal (average value) and noise (standard deviation). Results indicate a large dispersion of data, ranging from large positive to negative offsets, while most of the records depict in fact very similar values for the two periods. This feature reflects the spatial heterogeneity of the response to climate changes, making the establishment of large-scale patterns particularly difficult. In a given region, differences also emerge between records from different archives (e.
Changes between the LGM and MH Due to the limited amount of well-dated marine δ 18 O records covering both the LGM and present day with more than one data point, we compare the LGM and the MH for investigating the isotopic amplitude of last termination (Fig. 10 ). The LGM-MH comparison reveals a significant negative (positive) offset in almost all the terrestrial (marine) records, with only few speleothem and coral records showing the opposite trend, mostly in the subtropics, where they may reflect precipitation or atmospheric circulation effects rather than local temperature variations. The highest deglacial amplitude is recorded in highelevation and polar ice core records, while the offset is less marked in oceans and speleothems. Marine datasets reveal a latitude-independent general amplitude of ∼ 1.
45 ‰ (1. 55 ‰ when considering only foraminiferal records, with a similar average value for benthics and planktonics), out of which ∼ 1 ‰ is due to the change in land ice volume. In addition, we observe specific regional patterns. Larger amplitudes are identified in marine records from the north and southeast Atlantic (about 1. 7 ‰), which contrast with smaller amplitudes in the tropics (∼ 1. 5 ‰) and maximum signals in the Mediterranean Sea (about 2. 5 ‰). In this basin, this strong isotopic change is understood to reflect large SST deglacial warming and salinity changes induced by shifts in the regional atmospheric circulation  (Bigg, 1994; Emeis et al. , 2000; Hayes et al. , 2005; Mikolajewicz, 2011). Statistics based on benthic foraminiferal δ 18 O records (including datasets presenting only one data point in the periods of interest) reveal that there is no influence of core site depth on the amplitude of the LGM to MH transition (R 2 = 0.