Disentangling climatic and anthropogenic controls on global terrestrial evapotranspiration trends

We examined natural and anthropogenic controls on terrestrial evapotranspiration (ET) changes from 1982 to 2010 using multiple estimates from remote sensing-based datasets and process-oriented land surface models. A significant increasing trend of ET in each hemisphere was consistently revealed by observationally-constrained data and multi-model ensembles that considered historic natural and anthropogenic drivers. The climate impacts were simulated to determine the spatiotemporal variations in ET. Globally, rising CO2 ranked second in these models after the predominant climatic influences, and yielded decreasing trends in canopy transpiration and ET, especially for tropical forests and high-latitude shrub land. Increasing nitrogen deposition slightly amplified global ET via enhanced plant growth. Land-use-induced ET responses, albeit with substantial uncertainties across the factorial analysis, were minor globally, but pronounced locally, particularly over regions with intensive land-cover changes. Our study highlights the importance of employing multi-stream ET and ET-component estimates to quantify the strengthening anthropogenic fingerprint in the global hydrologic cycle.Terrestrial Ecosystem Science Scientific Focus Area (SFA) - Terrestrial Ecosystem Science (TES) Program in the Climate and Environmental Sciences Division (CESD) of the Biological and Environmental Research Program; Biogeochemistry-Climate Feedbacks SFA - Regional and Global Climate Modeling (RGCM) Program in the Climate and Environmental Sciences Division (CESD) of the Biological and Environmental Research Program in the US Department of Energy Office of Science; Regional and Global Climate Modeling (RGCM) Program in the Climate and Environmental Sciences Division (CESD) of the Biological and Environmental Research Program in the US Department of Energy Office of Science [DE-SC0012534]; National Aeronautics and Space Administration (NASA) [NNX12AP74G, NNX10AG01A, NNX11AO08A]; NASA; NASA ROSES [NNX10AG01A, NNH10AN681]; Natural Sciences and Engineering Research Council (NSERC) of Canada; US Department of Energy (DOE), Office of Science, Biological and Environmental Research; DOE [DE-AC05-00OR22725]; US Department of Energy (DOE), Office of Science, Biological and Environmental Research (BER) through Earth System Modeling program; U.S. DOE-BER; U.S. DOE-BER through Subsurface Biogeochemical Research Program (SBR) as part of the SBR Scientific Focus Area (SFA) at the Pacific Northwest National Laboratory (PNNL); US DOE by BATTELLE Memorial Institute [DE-AC05-76RLO1830]; NASA Interdisciplinary Science Program (IDS); NASA Land Cover/Land Use Change Program (LCLUC); NASA Terrestrial Ecology Program; NASA Atmospheric Composition Modeling and Analysis Program (ACMAP); NSF Dynamics of Coupled Natural-Human System Program (CNH); Decadal and Regional Climate Prediction using Earth System Models (EaSM); DOE National Institute for Climate Change Research; USDA AFRI Program; EPA STAR Program; US National Science Foundation [NSF-AGS-12-43071, NSF-EFRI-083598]; USDA National Institute of Food and Agriculture (NIFA) [2011-68002-30220]; US Department of Energy (DOE) Office of Science [DOE-DE-SC0006706]; NASA Land cover and Land Use Change Program [NNX14AD94G]; Office of Science of the US Department of Energy [DE-AC02-05CH11231]; National Science Foundation [OCI-0725070, ACI-1238993]; state of Illinois; GhG Europe FP7 grant; US Department of Energy [DE-AC05-00OR22725]; DOESCI(E)EIARTICLEmaoj@ornl.gov91