Response of terrestrial aridity to global warming

Dr. Qiang Fu, Professor, Department of Atmospheric Sciences, University of Washington

Abstract for Weekly Colloquium on Thursday, November 2, 2017 at 4 pm in Harshbarger 206 ~ Refreshments at 3:45 pm

The dryness of terrestrial climate can be measured in terms of an aridity index that is the ratio of annual precipitation to potential evapotranspiration. United Nations Environment Programme defines drylands as the terrestrial areas with an aridity index of less than 0.65, which are further classified into hyper-arid, arid, semiarid, and dry sub-humid lands.  In this talk I will present the response of terrestrial aridity and dryland areas to global warming based on both observations and modeling in the framework of the UNEP aridity index. A mechanism that “warmer is more arid” will be discussed.  It will be shown that global drylands have expanded in the last sixty years and will continue to expand in the 21st century. By the end of this century, the world’s drylands under a high greenhouse gas emission scenario are projected to be about 10 % larger than in the 1961–1990 climatology. A response of terrestrial aridity to aerosol radiative forcing will also be discussed.