Sara Pryor

Wind speeds in the United States seem to be slowing, and global climate change may be the cause.

In a study to be published in the August issue of the Journal of Geophysical Research, IU researchers and others evaluate and compare an extensive range of wind speed data sets taken from the contiguous United States over a period of more than 30 years. Sara Pryor, professor of atmospheric science in the Indiana University Bloomington Department of Geography, is the study's lead author.

Wind speeds may not seem to be a critical aspect of climate change, but Pryor notes that alterations in wind speed are highly relevant to industries such as insurance, construction, maritime, and agriculture, not to mention the burgeoning wind energy industry.

"Near-surface wind speeds are of great importance in dictating possible impacts of global climate change and developing robust assessments of the contemporary wind climate," writes Pryor with her co-authors, including Rebecca Barthelmie of the IUB Department of Geography and Duick Young, a doctoral student in the department.

Although the new study is preliminary, in their comparison and analysis of an extensive range of wind-speed data, Pryor and her co-researchers found statistically significant declines since 1973. The largest magnitude of decreasing wind speed was over the eastern United States, particularly the Midwest, including states such as Ohio, Indiana, Michigan, and Illinois.

"The stations bordering the Great Lakes do seem to have experienced the greatest changes," Pryor told the Associated Press for a June 10 story. The likely explanation is that there is less ice on the lakes, and wind moves faster across ice than it does over water.

Changes in air temperature affect air pressure which in turns affects the strength of wind. "It's a very large effect," noted Pryor's co-author Eugene Takle, a professor of atmospheric science at Iowa State University, in the AP story. In some places in the Midwest, the trend shows a decrease of 10 percent or more over a decade.

Atmospheric scientists disagree on whether wind really is slowing down because of climate change, but Pryor and her colleagues hope their work will provide a "platform for evaluation of models being used to estimate possible future wind speed regimes under global climate change scenarios."

Climate change in the Midwest is also the focus of a new book Pryor has edited, Understanding Climate Change: Climate Variability, Predictability, and Change in the Midwestern United States. A detailed assessment of various changes in the Midwestern climate system, Pryor's book will be published by Indiana University Press in July 2009.