Detecting Anthropogenically Induced Changes in Extreme and Seasonal Evapotranspiration Observations

Flash droughts are rapid-onset droughts that develop within days to a week. However, they are rarely studied through the lens of evapotranspiration (ET), the dominant flux driving changes in terrestrial water storage during such events. Here, we present a novel view on flash droughts by studying high ET extremes using both climate models and observational data. The identified high ET extremes are driven by periods with high incoming surface radiation and temperatures. Consistent with physical understanding these events are intensified by anthropogenic climate change. For the first time, we detect a robust change in extreme and seasonal ET in two observational datasets. Regionally, seasonal mean ET shows mixed increases and decreases from 1980 to 2023 depending on water supply and demand, while extreme ET universally increases due to increasing water demand. We expect regions with strong extreme ET trends to be at increased risk for flash droughts, as hydrological variability increases.