But, Its a Dry Heat... Climate Warming, Increased Aridity and its Impacts in Southwestern North America

GLEN M. MACDONALD, Director, Institute of the Environment, UC-Los Angeles Professor, IoE, Dept. of Geography, Dept. of Ecology and Evolutionary Biology, UCLA

Monday, October 19, 2009
4:00 PM - 5:15 PM
La Kretz Hall 110

Climate models predict that as temperatures rise in the 21st century large areas of the subtropics, including Los Angeles and southwestern North America in general, will become increasingly arid. The potential geographic scope of this aridity extends from Southern California to the headwaters of the Colorado River - impacting local to extra-regional water sources. We have already over-allocated Colorado River water and northern California sources are under pressure for a number of reasons. How the Pacific Ocean and the Pacific Decadal Oscillation and the ENSO system will respond to warming remains uncertain. If the eastern tropical and extra-tropical Pacific were to cool relative to the west it could exacerbate aridity in places like southwestern North America - but could mitigate drying in places like India. One way of examining potential hydroclimatic and Pacific Ocean responses to warming is to use paleoclimatic records to look at past period of natural temperature increase and their impacts. Paleoclimatic studies using a number of different types of evidence suggest that periods of warming over the past 12,000 years are typically associated with increased aridity in California, often exacerbated by a relative cooling of the eastern Pacific.