Although global climate models generally reflect increasing precipitation over land with anthropogenic warming, the projected faster increase in evaporative demand actually leads to an overall increase of aridity. Studies of the land region aridity increase with warming have largely emphasized the driving role of oceanic warming and associated atmospheric processes in leading to land surface drying. However, a recently published study in Nature Climate Change, co-authored by EOAS affiliate Benjamin Lintner, describes how the aridity response is substantially amplified by land–atmosphere feedbacks associated with the land surface’s response to climate and CO2 changes.
As the climate warms, soil moisture is generally projected to decrease globally. Using targeted climate simulations from the “Global Land Atmosphere Coupling Experiment – Coupled Model Intercomparison Project Phase” (GLACE-CMIP5), this study finds that decreasing soil moisture feeds back on the near-surface atmosphere, making it warmer and less humid, thereby enhancing aridity. Similarly, the study finds that aridity is enhanced by the physiological impact of increasing atmospheric CO2 on vegetation, which reduces transpiration from plants and renders the near-surface atmosphere drier. The overall picture suggested by this study is thus one of ocean warming and atmosphere processes leading to an initial increase in land region aridity but with land-atmosphere interactions playing an key role in determining the magnitude of the response.
To read more, the full article can be found here.
A. Berg, K. Findell, B. Lintner, A. Giannini, S. I. Seneviratne, B. van den Hurk, R. Lorenz, A. Pitman, S. Hagemann, A. Meier, F. Cheruy, A. Ducharne, S. Malyshev and P. C. D. Milly (2016). Land-atmosphere feedbacks amplify aridity increase over land under global warming, Nature Climate Change, http://doi.org/10.1038/nclimate3029