Investigations on the Aridity Paradox

Thursday, 18 December 2014
Randall J Donohue, CSIRO Land and Water Canberra, Land and Water Flagship, Canberra, Australia and Michael L Roderick, Australian National University, Canberra, Australia
How global aridity might change in the immediate future is an important question. Several recent analyses have concluded that aridity will, in general, increase over land primarily because of increasing vapour pressure deficit. Taken at face value that result is difficult to understand because a warmer world is also anticipated to be a moister world. For example, at the global scale, climate model projections are for increasing rainfall and runoff. In this presentation we investigate this seeming paradox. We find that the previous analyses have not accounted for the biological impacts of elevated CO2 and when that is incorporated, the climate model projections are for a modest reduction in meteorological and hydrologic aridity and for larger reductions in biological aridity.