Drought SPEI 6 and 12 return periods under historical and future climate scenarios

This dataset contains return-period levels for SPEI (6- and 12-month) derived from NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP-CMIP6, v1.2), via Araujo et al (2025) Global Future Drought Layers Based on Downscaled CMIP6 Models and Multiple Socioeconomic Pathways, for historical and future epochs under various climate scenarios, for the ensemble of available models. Return levels are estimated by fitting a generalized Pareto function to each epoch/scenario/model monthly SPEI timeseries, to estimate 20, 50, 100, 200, 500, 1500 year exceedance levels, using the scripts in https://github.com/nismod/CCG-Climate-Data/