dataesr/scientific-paragraphs-categorization huggingface dataset:
Geographic coverage. The Temperature 12k database gathers paleotemperature data from every continent and ocean. The geographical distribution of the records, however, is uneven (Fig. 2 ). Latitudinally, 51% of the sites are located within the zone of 60-30°N, and only 16% are located in the Southern Hemisphere (Fig. 3 ). The spatial density of sites is comparatively high in North America and Europe and lower across the open ocean and tropical Africa. Data-poor regions reflect a combination of physical impossibility to obtain proxy records (e. g. , low sediment accumulation rates in the open ocean and paucity of biogenic materials from extreme environments such as deserts), limited research attention and, in some cases, restricted field and data accessibility (e. g. , Siberia). record length and resolution.
The temporal distribution of the time series is relatively uniform (Fig. 2b ), with different proxy types having similar record lengths. The average record length within the Holocene is 9813 years for this database (n = 816, where only one season (or annual) is counted for each proxy from each site). All sites are represented by records that include at least some data between 8. 5 and 3. 5 ka. The number of records decreases over the last millennium, especially over the past century, largely because the surface sediment from lakes and oceans are watery and therefore difficult to recover intact, or because the climate interpretation of recently accumulated sediment has been compromised by human activities. Most of the records (91%) extend back at least 6000 years, thereby encompassing the '6 ka time slice' , which is an on-going and long-standing target for paleoclimate modeling  24.
The temporal distribution of time series contrasts with paleotemperature data from the past 2000 years  9  , which are dominated by tree-ring records less than 500 years long. This underscores the complementary information afforded by this database when combined with the PAGES 2k Consortium  9. The median record resolution (Suppl. Table  1 , 'Resolution') of individual time series in the database is 164 years over the Holocene (n = 816, where only one season (or annual) is counted for each proxy from each site) (Fig. 3b ). Overall, 15% of these records have 50-year resolution or finer, 39% have 51-to 150-year resolution, and 21% are coarser than 250-year resolution. Seasonality. Most of the sites (74%) include at least one record that was interpreted as mean annual temperature, or was calculated as the average of summer and winter values for this data product to represent annual temperature.
Most of the sites (64%) have records that are interpreted by the original authors as representing summer temperature, and 39% of the sites include winter paleotemperature estimates. The temporal distribution of records by season through the Holocene (Fig. 2c ) shows relatively uniform distribution of seasonal paleotemperature records. chronology. The majority of records in this database are based on sedimentary sequences dated by radiocarbon, and their time series are calibrated to calendar years relative to 1950 CE (BP). Some of the age-depth models are supported by volcanic ash (tephra) whose ages are known, some are augmented by biostratigraphic markers (first-arrival datums for pollen records), and some have  210  Pb profiles constraining the age of surface sediments. Speleothems are dated by U/Th methods, and some sequences are annually laminated (varves, ice, wood).
For sequences that rely mainly on radiocarbon (n = 613), the average number of ages for records in this database is 1. 0 per 1000 years, including the tephra ages. Recalculated age models based on a Bayesian modeling routine  18  are available for many of the time series, including the marine records from the ongoing DADT project (records with 'Calibration Method' = 'Bay. '), and McKay et al. 's Arctic Neoglacial study  25. The age ensembles are made available as part of the expanded data package for this data product (see below).
technical Validation Confirmation that the Temperature 12k dataset accurately represents the temperature at a site or globally would require knowing the actual temperature through time. This can only be determined for the period of instrumental temperature observations. Only a few of the records in this database include a sufficient number of inferred temperatures (samples) over the period of thermometer-based temperature observations for such a determination. In fact, the number of records that include data over the 20 th Century is less than any other century of the past 10,000 years. Instead, evidence that the records in the database reflect past temperature fluctuations at each site can typically be found in the original publications associated with each record (Suppl. Table 2, refs. ).
Th This procedure relies on expert knowledge as represented in peer-reviewed literature to guide the selection of proxy records. Records were not selected or weighted based on how well they correlate with an instrumental target. Expert knowledge can indeed yield a stronger proxy network for paleoclimate reconstructions than screening against instrumental data alone  567. The validation approach used here focuses on the robustness of the major trends that characterize this diverse dataset. For this, the database was subdivided and summarized statistically to evaluate the extent to which a common signal is represented by various categories of records, or whether the major features of the overall signal are strongly controlled by a particular subset of the records. We also test whether the spatial network of sites in this database is sufficient for representing large areas of the globe; for this, we focus on 30° latitudinal bands, following previous reconstructions of global temperature for the Holocene 5 and the deglacial period  568.
Quality control procedures. The authors of this data product worked in four teams of proxy experts (marine, pollen, chironomid, and other terrestrial archives) to assemble and quality control the data and metadata. They used a web-based data viewer (LiPDverse. com) and other visualization tools to examine displays of the raw data and the metadata. They reviewed the primary literature to assure that the data met the selection criteria for this database. The metadata (Suppl. Table  1 , 'QC Certification') lists the initials of the author(s) of this data descriptor who certified that each proxy record was translated accurately to the database, and that it was interpreted in the literature as related to temperature, and who, in some cases, added notes to help assure appropriate reuse of the data ('QC Comments').
Robustness of major trends represented in different subsets of records. Composite time series were generated to characterize the major overall trends in the time series that comprise the dataset and to compare signals contained in various subsets of the database. Compositing procedures. Our approach follows the data descriptor of the PAGES 2k Consortium 9 temperature database. Briefly, all time series were standardized to z-scores, with a mean of zero and variance of 1 SD over the entire record length (except for the global composite, as specified below). Individual data points were binned by averaging the measurements within 500-year intervals (except for the high-resolution composite described below). We chose 500 years because it is compatible with the minimum 400-year-resolution selection criterion for records in this database, and because this broad bin size substantially mitigates the influence of age uncertainties.
The binned records were then gridded spatially using an equal-area grid (4000 grids, each with area = 127,525 km 2 , following methods in ref. 12  ) to reduce the influence of clustered sites on the composites (except for the proxy-specific composites). The binned time series of various types (as specified below) inside each grid cell were averaged. The gridded data were also averaged into 30° latitudinal (zonal) bands to yield a single composite. Composite uncertainties. The database contains a wide range of inter-record variance, which necessitates a large sample size to reconstruct regional or global temperature history. The uncertainty in the mean value of the composite at any time is related to both the number of records and their dispersion. To quantify this uncertainty, we used a bootstrap procedure that randomly sampled the proxy data network to generate an ensemble of composites from which the uncertainty was calculated.
The procedure samples with replacement 570 whereby the number of randomly selected records equals the total number of records, but individual record could be selected more than once in a given bootstrap sample. The procedure was repeated to generate 1000 datasets from which composites were calculated and the mean and 95% uncertainty intervals were derived. The uncertainty intervals generated by this procedure are widest where a composite is represented by the fewest records and where there is therefore less certainty in the mean value. This approach is different than representing uncertainty according to the dispersion among records, which may not fully reflect the confidence in the mean estimate. Composite seasonality. Unless otherwise specified, the composites were based on annual records.
Therefore, summer records located in the tropics may be good surrogates for mean annual temperature, but less so for records located on Northern Hemisphere continents. Even for records that have been calibrated to annual temperature, the extent to which they accurately represent annual temperature depends on multiple factors, including assumptions that underlie the calibration procedures and the part of the seasonal cycle that influences each type of proxy sensor. Comparison among proxy types. To evaluate the extent to which different proxy types carry a common overall signal, composites were calculated for each of the eight most common proxy types in the database (Fig. 4 ). No spatial gridding was applied prior to averaging for this comparison so as not to confound the direct comparison among proxy types.
'Proxy General' = 'other biomarkers' includes TEX 86 , GDGT, BNA15, LDI, but not alkenones, which are treated separately. 'Proxy General' = 'other ice' includes boreholes, bubble frequency, gas diffusion, melt-layer frequency, etc. , but not isotopes. Refer to Suppl. Table  1  for details. (c) Temporal availability of records by seasons (Suppl. Table  1 , 'Season General'). Both annual and seasonal records from the same site are included (n = 1319). For these comparisons, the temperature of the grid cells nearest to each proxy-record site were averaged and compared with global and zonal mean temperatures within both the PMIP3 mid-Holocene simulations and the instrumental temperature data over the past 150-100 years. The comparisons show that, within the simulated and reanalysis datasets, the temperatures at the network sites correlate essentially one-to-one with the zonal and global temperatures.
Usage Notes Uncertainties. This database is presently the most comprehensive compilation of a globally distributed, multi-proxy, quality-controlled Holocene paleotemperature time series. It includes records from a variety of terrestrial and marine proxy types, each based on their own principles and procedures, and all of them associated with an extensive literature. Background information about the proxy types and their underlying assumptions is available in textbooks devoted to the topic (e. g. , ref. 576  ), and specific information about each proxy record is available through the original publications (Suppl. Table  2 , refs. ). In In addition to the variety of proxy types, there are a variety of approaches used to characterize uncertainties related to paleotemperature interpretations. There are no standard procedures for either calculating or reporting uncertainties, with some procedures taking analytical uncertainty into account and others focusing on the conversion of proxy measurements into absolute temperature.
In most cases, the original studies describe the uncertainties associated with each proxy climate record. Fig. 3  Latitudinal distribution of records. Frequency of records partitioned in 30° latitude bands according to their (a) archive type (Suppl. Table  1 , 'Archive Type'), and (b) temporal resolution (Suppl. Table  1 , 'Resolution'). Only one seasonal (or annual) record is counted for each proxy type from a site. Resolution calculated as the median spacing between consecutive proxy samples of each time series, back to 12,000 years. Among the important uncertainties to consider when using this database are those related to (1) calibration and proxy biases, (2) chronology, (3) spatiotemporal coverage. Depending on the scientific goal, uncertainties related to these and other factors can be substantial.
These two approaches are referred to as "calibration in time" and "calibration in space, " respectively. Uncertainties reported for paleotemperatures based on calibration-in-time procedures are typically relatively small because the method is tuned to reconstruct temperature variability at a single site, although this characterization does not represent all potential uncertainties  577. In contrast, uncertainties typically reported for calibration-in-space procedures are usually characterized by larger but more globally applicable uncertainties, as the proxy-environment relation is examined over a wide environmental gradient. In this database, author-reported temperature uncertainties are included when they were readily available, which was infrequently and based on a variety of approaches.
Shading indicates 95% bootstrap confidence intervals with 1000 replicates. Gray bars indicate the number of records per bin. Specific proxy types are combined or treated separately depending on the number of records available (Suppl. Table  1 , 'Proxy General' and 'Proxy Type'; see Fig. 2  for explanation). proxy type (e. g. , ref. 5  ). Others apply a single statistical method to calculate uncertainties for published proxy data, often employing expanded calibration datasets and new statistical methods (e. g. , ref. 7  ). 1] [22] [23]. For other proxy types, paleotemperature values and their uncertainties are based on multiple generations of analytical and calibration methods. Biases can arise when proxy types that are most sensitive to summer conditions, common for biological indicators, are scaled to represent mean annual temperatures.
g. , pollen), and (2) the uniformity of the accumulation rate of the archival medium (dominantly sediments in this database), which governs the accuracy of the interpolated ages of samples between control points  13. Relative to these uncertainties, the analytical precision of the age determinations is typically minor. The inclusion of the primary chronology data and Bayesian-derived age ensembles for many time series in this database allows users to quantify and incorporate many, but not all, aspects of the age uncertainty into their own analyses. Uncertainties related to spatiotemporal coverage. The suitability of the database to address different scientific questions depends on the particular spatial and temporal scale. Some regions are covered more densely than others, and the number of records available decreases as the demands for temporal resolution increase.
At finer spatial and temporal scales, the number of records with sufficient resolution and geochronological control is limited and typically based on more recent studies. For example, only about 39% of the sites have records with resolution finer than 100 years. Future directions. The Temperature 12k database will form the foundation for new studies of Holocene global and regional surface temperature changes, and will help identify future research priorities. This machine-readable database includes multiple parameters for searching and filtering the proxy records, depending Fig. 6  Comparison between records from terrestrial versus marine sites. Composite time series subdivided terrestrial versus marine archives. Marine sites include some terrestrially based proxy types, such as pollen and some biomarkers; these are represented by 'Climate Variable Detail' = 'air@surface' rather than 'sea@surface' (Suppl.
g. , dated moraines). In the future, such information can be compared with the time-series data in this database to provide a more robust interpretation of past climate changes (e. g. , across Alaska 578 , Arctic Canada and Greenland  579  , and North Atlantic and Fennoscandia  580  ). The simplistic time-series composites included in this data descriptor provide insights into the large-scale patterns of the proxy data, and provide a basis for comparison among different subsets of the diverse database. The area-weighted composite (Fig. 8 ) also serves as an initial approximation of the global mean surface temperature over the Holocene. This provides a foundation for a more in-depth analysis of temperature history based on this database, including a comparison of statistical methods for reconstructing global mean surface temperature.
The Temperature 12k database represents a concerted effort to generate a comprehensive product, but it is an ongoing effort, with new records continuing to be published. The database includes a large proportion of available published records that meet the selection criteria and that were recovered by the authors of this data product. Fig. 7  Comparison between low-and high-resolution records. Composite time series (standard deviation units; left side y-axis) for high-resolution versus low-resolution records binned at 100 and 500 year intervals, respectively. Cut-off between high and low resolution was set as 100 years (median difference between consecutive observations). Symbols and procedures as in Fig. 5. Some published records that meet the criteria might have been inadvertently overlooked.
Readers who know of missing datasets, especially those from data-poor regions, or who find errors in this version are asked to contact one of the primary authors so that future versions of the database will be more complete and accurate. Rather than issuing errata to this publication, errors and additions will be included in subsequent versions of the database and updated through the online data repository (see below). ancillary data. Additional records within the temperature 12k datasets. In addition to the paleotemperature records used in the Temperature 12k compilation, the LiPD files also contain ancillary data from the same sites. For some sites, these include the native observations used to derive the paleotemperature values (e. g. , Mg/Ca of foraminifera), or other data that are not directly related to climate but represent environmental changes at a study site that might be useful in interpreting the climatic significance of the record (e.
g. , sedimentary magnetic susceptibility). Some LiPD datasets include proxy data that are sensitive to climate variables other than temperature. These ancillary data are made available along with this data product, but have not been reviewed for accuracy, and some, including most of the pollen-based precipitation records, have not been vetted by peer review. Within the LiPD files, the records that comprise v. 1. 0. 0 of the Temperature 12k database and were used to generate the figures in this data descriptor are discoverable in ref. 7  by filtering the metadata field, 'In Compilation' = 'Temp12k'. Temperature-sensitive records in addition to temperature 12k datasets. This database is a quality-controlled and curated subset of data culled from a larger collection of proxy climate data (LiPDverse.
org), all structured in LiPD. Many temperature-sensitive proxy records that were gathered as part of this project do not meet the selection criteria for length, resolution, or age control as prescribed for this database. These data are likely useful for addressing scientific objectives that are outside the scope of this compilation. Many of the records have been reviewed by the authors of this data product, as indicated by their initials in 'QC Certification, ' but most have not been reviewed for accuracy. Nonetheless, these data, including about 1110 records from over 560 sites are made available as part of the overall database of temperature-sensitive records. Within the LiPD files (ref. 7 , www. ncdc. noaa. gov/paleo/study/27330) these are discoverable by filtering the metadata field, 'In Compilation' = 'Tverse'.
Ensemble paleotemperature time series and age models. To characterize and quantify uncertainties associated with both chronologies and paleotemperatures, recent paleoclimate studies have featured ensembles of age models and proxy time series, most commonly derived from the posterior distribution of Bayesian statistical methods. Many of the datasets in the Temperature 12k database include age or temperature ensembles, or both. These are included in the expanded version of the Temperature 12k database (Table  2 ). Most of the age ensembles are associated with previous studies that recalculated age models based on the 'Bacon' modeling routine  18. These are available for many of the time series, including the marine records from the DADT project (records with  Database format and operability.
The site-level proxy and geochronology data and metadata are formatted in the Linked Paleo Data (LiPD) structure. The LiPD framework comprises JSON formatted, standardized files that are machine-readable in multiple programming languages for querying and data extraction  10. The hierarchical structure allows explicit descriptions at any level and aspect of the database, thereby providing a flexible structure that can accommodate a variety of data and metadata types. The LiPD files comprising this database have also been excerpted and translated into the format of the World Data Service (WDS) NOAA Paleoclimatology where they are archived for long-term reuse. be posted at WDS-NOAA Paleoclimatology. The landing page links to digital versions of the Temperature 12k database, including the metadata in Suppl.
WDS-Noaa-paleoclimatology Landing page contents. Versioning scheme. The database versioning scheme for this data product follows the one proposed by McKay and Emile-Geay 10 and used for the PAGES 2k Consortium 9 temperature database. The version number is in the form C1. C2. C3, where C1 is an integer associated with a publication, 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. The dataset published here is thus v1. 0. 0 of the Temperature 12k database. Future versions, along with a change log that specifies the modifications associated with each version, will be posted on the WDS-NOAA Paleoclimatology landing page. This versioning applies only to the temperature-sensitive records marked as 'In Compilation' = Temp12k; changes to ancillary time series are not tracked.
Brief description of selected metadata fields used in the Temperature 12k database and shown in Suppl. Table1. sub-millennial patterns, we selected time series with sample resolution ('Resolution') finer than 400 years (i. e. , the median spacing between consecutive samples is less than 400 years over the past 12,000 years or over the full record length, if shorter). For some records, the selection cut-off values for duration and resolution were relaxed to improve the global coverage of the data network, especially in the Southern Hemisphere. These records are identified as such in 'QC Comments. '.