High-resolution satellite imagery reveals a recent accelerating rate of increase in land evapotranspiration

Over the past two decades, climate change has led to the intensification of the hydrologic cycle and greatly altered global land evapotranspiration (ET). Existing low-resolution evapotranspiration datasets, though valuable for global estimates, does not fully capture spatial heterogeneity and local-scale effects, necessitating the need for higher-resolution assessment of field-scale ET for enhanced accuracy. Here, we examine trends in global land ET over the past three decades using more than four million thermal Landsat satellite images. We employ the validated and scalable Hybrid Single-source Energy Balance model (HSEB) to generate the first monthly 100m resolution ET dataset from 1990 to 2021, allowing us to examine the inter and intra-annual variability in global land ET trends. Our analysis unveils a significant global increase in ET over the last two decades at an annual rate of 1.33 (+/- 0.84) mm yr(-1) (0.2 %), despite regional disparities. This rate intensifies to 0.47 % and 1.97-2.15 % in the recent twelve and seven years of the study, mainly due to summer ET increases over North America, African tropics, and Indochina. We show that 21 % of the land area experiences a notable increase in evapotranspiration, notably in regions like Amazonia, Congo, Southeast and Midwest North America, Mediterranean Europe, and central China, while 11.6 % shows a significant decrease, particularly in southwestern North America, Southern South America, western Russia, and parts of West Asia. Tropical and subtropical regions exhibit the most pronounced increases. In recent years, the increase in vapor pressure deficit and greening, fueled by rising temperatures, align with the positive global ET trend. Our study signifies the profound influence of climate change on evapotranspiration. The freely available dataset we generated can support water resources management and detailed global water use and drought mapping at unprecedented spatial and temporal scales.