Attributing future changes in terrestrial evapotranspiration: The combined impacts of climate change, rising CO₂, and land use change

Evapotranspiration (ET) is a crucial component of ecohydrological processes that can be significantly influenced by environmental drivers, including climate variability, elevating CO₂ concentration, and human-induced land use/land cover changes (LULCC). However, the mechanism and specific quantitative contributions of these drivers in shaping terrestrial ET remain highly uncertain within the context of future global changes. Here, we employed an integrated modeling framework that combines a process-based land surface model and a land use simulation model to comprehensively estimate and attribute future changes in global terrestrial ET for different Shared Socioeconomic Pathways and Representative Concentration Pathways (SSP-RCP) for the first time. We projected an increase in terrestrial ET of 0.17 to 0.60 mm yr⁻² from 2020 to 2100 under three SSP-RCPs. Specifically, climate change and CO₂ suppression effects exert primary (78.14 % – 78.37 %) and secondary (17.99 % – 21.44 %) influences on this increase, respectively. LULCC has a relatively minor impact on terrestrial ET variations (0.19 % to 3.88 %), and dominates ET across 0.64 % to 4.74 % of the global land area. In tropical regions like South America, LULCC can account for up to 17.77 % of ET changes under a medium development scenario (SSP2–4.5). Our study enhances the comprehension of combined and individual impacts of climate change, rising atmospheric CO₂ concentration, and LULCC on future terrestrial ET, and underscores the crucial role of LULCC at regional scales.