Transpiration accounts for two thirds of global terrestrial evaporation

Even though the contributions of transpiration (T), soil and lake evaporation (E), and interception (I) to terrestrial evapotranspiration (ET=T+E+I) is crucial for understanding the hydrological cycle and its connection to ecological processes, the ratio T/ET is unattainable by traditional measurement techniques over large scales. The global mean T/ET from multiple independent sources, including satellite-based estimation, atmospheric reanalysis, land surface models, and isotopic measurements, varies substantially from 24% to 90%. Here we develop a new ET partitioning algorithm, which combines global evaporation estimates as well as leaf area index (LAI) and T/ET relationships of different vegetation types based on a wide range of site measurements from published studies. We show that transpiration accounts for two thirds of global terrestrial ET (65.5±4.6%). Our results bridge the scale gap between site measurements and global model simulations and indicate a major role played by vegetation in global terrestrial hydrology. Our approach can be implemented into current global climate models to improve biological carbon flux simulation.