4:00 THURSDAY, 7 NOV. 2002 Center Hall 109

PHYSICS COLLOQUIUM

Richard C.J. Somerville/SIO

"Can Climate Models be Trusted?"

ABSTRACT: What will the climate of the 21st century be? If the latest computer simulations of climate are right, then humankind has already entered a new era, one in which our species is no longer a passive spectator at the natural pageant of climate change. Instead, we have moved onto the stage ourselves to become actors, and by burning fossil fuels we have enhanced the natural greenhouse effect and already altered the climate. Furthermore, we have committed our children and grandchildren to a world in which temperatures will increase, snow and ice will melt, sea level will rise, and precipitation patterns will be disrupted. Are the computer models that tell this story reliable? How strong is the evidence for believing the scenarios they produce? Do poorly understood aspects of the climate system significantly affect the model results? What does current research promise for the future? This talk answers these questions and provides glimpses into ongoing research on the single most important known source of uncertainty in climate models: the role of clouds and cloud-radiation feedbacks in the climate system.