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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 CO 2 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 OPEN ACCESS RECEIVED 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 landcover changes. Our study highlights the importance of employing multi-stream ET and ETcomponent estimates to quantify the strengthening anthropogenic fingerprint in the global hydrologic cycle.Environ. Res. Lett. 10 (2015) 094008 J Mao et al

Validation of North American Regional Climate Change Assessment Program (NARCCAP) climate simulations is conducted for selected US Forest Service sites in the southeastern United States. Results focus on qualitative and quantitative comparisons of seasonal and monthly temperature data from NARCCAP simulations to the surface air temperature data sets developed at the University of Delaware. The Regional Climate Model, RCM3, driven by the Geophysical Fluid Dynamics Laboratory Global Climate Model underestimates average surface temperature for some areas of the southeast United States by about 4• C for the daily average during the winter of the selected period.

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