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Stephen J. Vavrus

Ph.D., Atmospheric Sciences, University of Wisconsin-Madison, 1997

Senior Scientist

Center for Climatic Research
1105 Atmospheric, Oceanic & Space Science Bldg.
1225 W. Dayton St.
Madison, Wisconsin 53706-1695

Phone: (608) 265-5279
Fax: (608) 263-4190

Research Interests

Climate change has emerged as one of the premier environmental concerns of our time, yet many uncertainties surround this issue. We are unsure, for example, of the rate and magnitude of change in polar regions, the role of clouds in tempering or enhancing greenhouse warming, the response and impact of future extreme events, and even the origin of anthropogenic influence on global climate.

My research addresses these questions using computer climate models of the earth system. I am investigating the response of polar clouds to future climate change and the feedback role they may play. One goal of this work is to improve how high-latitude clouds are simulated by general circulation models (GCMs). A related objective is to understand how clouds interact with their associated “accomplices” (e.g., water vapor, circulation, radiation, boundary conditions) to affect climate in the Arctic, a region that has been experiencing pronounced environmental change recently and is expected to see the most extreme changes in the future.

Within and beyond polar regions, climatologists, policy makers, and the general public are especially concerned about how future climate change will affect extreme weather events, such as heat waves, cold-air outbreaks, and floods. Variations in these infrequently occurring phenomena may have even greater societal and ecological impacts than changes in average climatic conditions. I am working with an interdisciplinary group of scientists and medical experts to investigate how changes in extremes will likely influence human morbidity as global warming ensues this century.

A revolutionary idea has recently been proposed by Dr. William Ruddiman that the origin of anthropogenic climate change reaches back much further in time (thousands of years ago) than the conventional starting point of the Industrial Revolution. The “Early Anthropogenic Hypothesis” posits that widespread deforestation and rice cultivation with the emergence of agriculture several thousand years ago led to a gradual but significant rise in atmospheric CO2 and CH4 and thus greenhouse warming. I am involved in a collaborative research project to test this hypothesis, using GCMs to simulate the present-day climatic conditions expected in the absence of early human land-cover modification.

Publications from these and other research projects can be found here.

Research Team