Future changes of global potential evapotranspiration simulated from CMIP5 to CMIP6 models

This research evaluated the ability of different coupled climate models to simulate the historical variability of potential evapotranspiration (PET) for the time period 1979-2017 in phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively). Their projected future changes of PET under two emission scenarios for the 21st century were also compared. Results show that PET has an increasing trend of 0.2-0.6 mm d(-1)/50 yr over most land surfaces and that there are clear regional differences. The future value of PET is higher in the CMIP6 multi-model simulations than in the CMIP5 ones under the same emissions scenario, possibly because CMIP6 models simulate stronger warming for a given forcing or scenario. The contributions of each individual climate driver to future changes in PET were examined and revealed that the surface vapor pressure deficit makes a major contribution to changes in PET. Shortwave radiation increases PET in most terrestrial regions, except for northern Africa, East Asia, South Asia, and Australia; the effect of longwave radiation is the opposite to that of shortwave radiation. The contribution of surface wind speed to PET is small, but results in a slight reduction.