Land-atmosphere feedbacks amplify aridity increase over land under global warming

The response of the terrestrial water cycle to global warming is central to issues including water resources, agriculture and ecosystem health. Recent studies1–6 indicate that aridity, defined in terms of atmospheric supply (precipitation, P) and demand (potential evapotranspiration, Ep) of water at
the land surface, will increase globally in a warmer world.
Recently proposed mechanisms for this response emphasize the driving role of oceanicwarming and associated atmospheric processes4,5. Here we show that the aridity response is substantially amplified by land–atmosphere feedbacks associated with the land surface’s response to climate and CO2 change.
Using simulations from the Global Land Atmosphere Coupling Experiment (GLACE)-CMIP5 experiment7–9, we show that global aridity is enhanced by the feedbacks of projected soil moisture decrease on land surface temperature, relative humidity andprecipitation.Thephysiological impact of increasing atmospheric CO2 on vegetation exerts a qualitatively similar control on aridity.We reconcile these findings with previously
proposed mechanisms5 by showing that the moist enthalpy change over land is unaected by the land hydrological response. Thus, although oceanic warming constrains the combined moisture and temperature changes over land, land hydrology modulates the partitioning of this enthalpy increase
towards increased aridity.