Ensemble of CMIP6 derived reference and potential evapotranspiration with radiative and advective components

Abstract

Assessing changes in future aridity requires an understanding of variations in the atmospheric demand for water. Such assessments are often driven by estimations of potential evapotranspiration (ETP) and/or reference evapotranspiration (ET0), yet no comprehensive and validated estimate of these climate metrics exists to date from the Coupled Model Intercomparison Project 6 (CMIP6). Here we describe the development and validation of a published dataset of global monthly estimates of the Penman-Monteith derived ET0, its advective and radiation components, Priestley-Taylor derived ETP, and vapor pressure deficit from 16 CMIP6 projections and four emissions scenarios. Historical validation of the ensemble of CMIP6 evaporative demand shows general agreement with observationally-derived baselines of ET0 and ETP from the Climate Research Unit (CRU) and ERA5-Land reanalysis products, with GCM biases driven primarily by regional differences in modeled humidity and advective contributions to ET0. Overall, evaporative demand is projected to increase across all emissions scenarios, with the largest increases over polar regions, and with a larger contribution from advection particularly for regions with higher baseline ET0.