Evidence for a recent increase in global land evapotranspiration from the mass-balance perspective

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 evapotranspiration products are derived from a variety of sources including models, remote sensing, and in situ observations, however upscaling these products is challenging, and as a result there is no consensus in global evapotranspiration variability and trends. Here we present an independent water-balance ensemble estimate of global land evapotranspiration with uncertainty distribution for 2003 to 2019 using data from the Gravity Recovery and Climate Experiment satellites (GRACE, GRACE-FO). We use multiple precipitation and runoff data sets to create an ensemble using the mass balance approach, and we compare the results with commonly used evapotranspiration products from remote sensing and land surface models (GLDAS, MOD16, FLUXCOM, PTJPL). Using results from our water balance ensemble, we show that global land evapotranspiration has increased by 10±1% between 2003 to 2019. We find that the interannual variability of global land evapotranspiration is greater for our mass balance calculated evapotranspiration, compared with existing products. Variability in global land evapotranspiration is positively correlated with the El Nino Southern Oscillation, however natural variability cannot explain the positive trend in evapotranspiration. Our results also suggest that global precipitation is increasingly partitioned into evapotranspiration rather than runoff. Our results serve as a top-down constraint on existing global land evapotranspiration products, and are also of importance for our understanding of global water cycle variability and change.