New evidence for recent increase in global land evapotranspiration

Accurate quantification of global land evapotranspiration is necessary for understanding variability in the global water cycle, which is expected to intensify under climate change. Current global evapotranspiration products are derived from a variety of sources including models, remote sensing, and in situ observations. But existing approaches contain extensive uncertainties, for example relating to model structure or the upscaling of observations to a global level; as a result, variability and trends in global evapotranspiration remain unclear. Here we show that global land evapotranspiration has increased by 10±2% between 2003 to 2019, and that precipitation is increasingly partitioned into evapotranspiration rather than runoff. Our results are based on an independent water-balance ensemble time series of global land evapotranspiration with uncertainty distribution, using data from the Gravity Recovery and Climate Experiment (GRACE) and GRACE-Follow On (GRACE-FO) satellites. Variability in global land evapotranspiration is positively correlated with the El Niño-Southern Oscillation. The main driver of the trend, however, is increasing land temperature. Our findings provide an observational constraint on land evapotranspiration, and are consistent with the hypothesis that global evapotranspiration should increase in a warming climate.