Stephen J. Vavrus

Senior Scientist

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

Nelson Institute 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 and is motivating climatologists to investigate how future climatic trends will unfold. My research addresses several key aspects of climate change, including the role of Polar Regions, the behavior of extreme weather, regional impacts around Wisconsin and the Great Lakes, and the origin of human-induced climate change. I address these questions mostly with computer climate models, which provide both quantitative estimates of future change and insights into the physical causes.

The Arctic

The Arctic is known to be Earth's most climatically sensitive region, but climate models differ on how rapidly the Arctic will change in the future and what societal impacts will result. I am researching these questions, including extreme sea ice variations and how atmospheric cyclones and winds may be affected by them. This research is closely aligned with the goals of the Study of Environmental Arctic Change (SEARCH), an interagency program designed to improve understanding of the processes and consequences surrounding Arctic change. I have served on its Science Steering Committee and participated in the related CLIVAR Working Group on Arctic Change and Possible Influence on Mid-latitude Climate and Weather that is interested in similar topics.

Extreme Weather

Global climate change is likely to affect extreme weather, but how this will occur is not clear. Some of my research focuses on how heat waves, cold spells, floods, and drought will respond to a changing climate, especially in the U. S. I am studying how amplified greenhouse warming in the Arctic might affect atmospheric circulation patterns and weather, both locally and remotely in middle latitudes. These regional climate change topics dovetail with my participation in, and co-directorship of, the Wisconsin Initiative on Climate Change Impacts (WICCI), a partnership between UW's Nelson Institute for Environmental Studies and the Wisconsin Department of Natural Resources.

Origin of Human Impact on Climate

A revolutionary idea proposed by Dr. William Ruddiman argues 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 global climate models to simulate the present-day climatic conditions expected in the absence of early human land-cover modification.

Madison and Wisconsin Climate Change

I am keenly interested in local and regional weather and climate variability, aided by the long records kept by the Wisconsin State Climatology Office. In particular, Lake Mendota's record of freeze-up and thaw dates extend to the early 1850s and serves as an indirect thermometer of past local weather conditions. I use these data to test models that simulate the behavior of ice cover on Mendota, including when ice forms and melts off each winter, as well as how thick the ice grows during the winter. In addition, I have constructed an index of extreme weather for Madison and Wisconsin that documents long-term trends in the amount and type of extreme weather.

Seasonal Weather Forecasting

I am involved in two multi-investigator projects to improve forecasts of the rainy season in southern Peru and Bangladesh to improve regional water resources management and better prepare for flooding. This work is funded by the Wisconsin Alumni Research Foundation and Southern Copper mining company, which needs information on whether the local rainy season (January-March) will be unusually wet, dry, or near normal.

Yahara Watershed Academy

I am serving as the coordinator of the Yahara Watershed Academy (YWA), an initiative created in a partnership among three area non-profits---Clean Lakes Alliance, Sustain Dane, and the Aldo Leopold Nature Center---and the Nelson Institute, Edgewood College, and Madison Metropolitan Sewerage District. The YWA trains students to become informed "watershed captains" who take action to improve the health of the Yahara Watershed. The inaugural YWA course took place in 2017, and the second course is happening in 2019.

Climate Change Education

In partnership with the Outrider Foundation, I have helped to develop an educational web site on climate change that describes actions individuals can take to help reduce our carbon footprints and actively engage on this topic.


Publications from my research can be found here: Steve's Papers.

File Server

Miscellaneous Files

Research Collaborators