A sensitivity study of the impact of dynamic vegetation on simulated future climate change over Southern Europe and the Mediterranean

Recent projections of climate change from general circulation and regional climate models over southern Europe and the Mediterranean basin show strong warming and pronounced decrease in precipitation over large portion of the region, especially in the summer. While the role of vegetation in modulating the region's climate is widely recognized, most, if not all, of these climate change projections do not account for the response of the dynamic biosphere to the potential climate changes. In this study we investigate the role of climate-vegetation interactions in a regional climate model (RegCM3) linked to a dynamic vegetation model (CLM-DGVM). High spatial resolution (20km) simulations of future climate with static vegetation (i.e. vegetation fixed at the present day state) show surface temperature increases across the entire southern Europe/Mediterranean domain in 2085-2089 relative to 1985-1989 due to the radiative and physiological effects of CO2 increase. In terms of precipitation the simulations exhibit substantial precipitation decreases for most of the domain and both summer and winter seasons. Accounting for the effects of structural vegetation changes significantly alters the simulated climate change effects over these areas, but most substantially over the Mediterranean where vegetation feedback reduces summer warming by 1K and reverts the 28% precipitation decrease to a 4% increase. These results emphasize the importance of including vegetation feedback in the projections of climate change impacts on the Mediterranean climate including extreme climatic events and storms.