Attribution of Global Evapotranspiration Trends Based on the Budyko Framework

Abstract. Actual evapotranspiration (ET) is an essential variable in the hydrological process, linking the carbon, water, and energy cycles. Global ET has significantly changed in the warming climate. Although increasing vapour pressure deficit (VPD) due to global warming enhances atmospheric water demand, it remains unclear how the dynamics of ET are affected. In this study, using multiple datasets, we disentangled the relative contributions of precipitation, net radiation, air temperature (T1), VPD, and wind speed on affecting annual ET linear trend using an advanced separation method that considers the Budyko framework. It is found that the precipitation variability dominantly controls global ET in the dry climates, the net radiation has substantial control over ET in the tropical regions, and VPD is impacting ET trends in boreal mid-latitude climate. The critical role of VPD in controlling ET trends is particularly emphasized due to its influence in controlling the land-atmosphere interactions.