PALEO-PGEM-Series: a spatial time series of the global climate over the last 5 million years (Plio-Pleistocene)

PALEO-PGEM-Series is a global spatiotemporal dataset of the climate over the last 5 million years, derived from the intermediate complexity atmosphere-ocean general circulation model PLASIM-GENIE using emulation and downscaling techniques (Holden et al. 2019). It consists of estimates of monthly temperature (in degrees Celsius), monthly precipitation (in millimeters), and 17 bioclimatic variables over the last 5 million years every 1,000 years at 1º x 1º spatial resolution.<br>We provide the mean and the standard deviation of the estimates across the 10 stochastic GCM emulation runs. We suggest that users take advantage of these uncertainty estimates by conducting sensitivity tests to assess how robust results derived using PALEO-PGEM-Series are in the face of emulation uncertainty.<br>Each .txt file contains 19,233 rows representing geographic grided cells and 5003 columns, the first two with coordinates (longitude and latitude) and the others with the estimates for each time slice, starting from 5,000,000 years and ending with the pre-industrial. Each column is named with “T” followed by a number representing the time in years divided by 1,000 (i.e., T5000 corresponds to time 5,000,000 years ago). These tables can easily be converted into spatial files (e.g., raster) and visualized and explored using GIS libraries. We also provide the data as netcdf raster files, which are included in the pastclim R package (<b>https://doi.org/10.1111/ecog.06481).</b><br>We provide an R script to derive the 17 bioclimatic variables from the monthly estimates (code adapted from the function <i>biovars</i> in R package <i>dismo</i>, Hijmans <i>et al.</i> 2021). These bioclimatic variables summarize central tendencies (e.g., annual means), seasonality (e.g., range of monthly means) and extreme conditions (e.g., maximum and minimum monthly means) of relevance for ecological and evolutionary studies. Mean diurnal range (BIO 2) and isothermality (BIO 3) cannot be derived from PALEO-PGEM-Series as they require diurnal cycles. Maximum (BIO 5) and minimum temperature (BIO 6) are modified versions of the original bioclimatic variables, as they are derived from monthly means and thus refer to the maximum and minimum monthly means of temperatures in the year. Consequently, the temperature annual range (BIO 7) is also with reference to monthly means.<br>