Many of the most important impacts of global warming will probably not be the actual changes in temperature, but the associated changes in hydrology. A warmer atmosphere can contain much more moisture, which we expect to make flash flooding more likely, but the global-mean rainfall is thermodynamically constrained to increase more slowly, so we expect a general tendency to increased drought as well.
Yet we cannot constrain any of this well on the more local scales where it matters, because precipitation has much smaller scales and stronger gradients than temperature, and is much more dependent on smaller-scale circulation and topography, and the agreement between different GCMs (General Circulation Models, the most detailed and physically-based models of climate) is correspondingly poorer.
HYDRA aims to attack this uncertainty by:
Principle Investigator: Prof Myles Allen
Professor Peter Cox, University of Exeter
Dr Hugo Lambert, University of Exeter
Dr Chris Huntingford, Centre for Ecology and Hydrology