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Hurricanes and Climate Change: A Sharper View

New Results Support Suggestions That Global Warming
Will Do Little To Change Hurricane Activity

hurricane

The figure shown is an example of one of the hurricanes generated in computer simulations produced by the Rosenstiel School team. Colors indicate the total amount of water vapor in a vertical column of the atmosphere; dark red areas would experience extremely heavy rainfall. The small size of each “pixel,” 3km by 3km, allows for remarkably accurate details in the storm. By comparison, the pixels used to represent such storms in global climate models are 100 km by 100 km in size, at best.

Virginia Key, Fla. (August 12, 2008) — In a study published in the July 2008 issue of Geophysical Research Letters, Drs. David S. Nolan and Eric D. Rappin from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science describe a new method for evaluating the frequency of hurricane formation in present and future tropical climates. While current thinking about changes in hurricane frequency comes mostly from computer simulations of global climate, the computer models used for these studies can only represent the coarsest features of hurricanes, thus casting doubt in their predictions of hurricane activity.

The new approach by Nolan and Rappin, developed in collaboration with Dr. Kerry Emanuel of the Massachusetts Institute of Technology, uses computer models with much more accurate representation of the processes that lead to hurricane formation, much the same way a digital image with more pixels allows for a more detailed photographic image. The models are used to simulate the rate of hurricane development in tropical atmospheres with varying values of sea surface temperature and vertical wind shear (which is the extent to which wind speed and direction changes with height in the atmosphere). These two variables — ocean temperature and wind shear — are considered to be the two most important factors in predicting hurricane activity, both in operational forecasting and in consideration of climate change.

“We designed the computer simulations to show that as the ocean temperature increased, hurricanes would form more rapidly and easily, even in the presence of wind shear,” says Nolan, associate professor of Meteorology at the Rosenstiel School. “Instead, we got exactly the opposite result. As the water temperature increased, the effectiveness of the wind shear in suppressing hurricane formation actually became greater.”

The simulations show that if they do form, hurricanes become stronger in the warmer environments. Together, these results suggest that in a global warming world, there would be less hurricanes, but those that do form could become stronger. The same prediction has recently been made by other studies using global climate models, and the similarity of the two predictions enhances confidence in the results.

“The additional aspect that our method offers is a much more accurate picture of the process of tropical storm and hurricane formation, as compared to the global models,” Nolan said. “Our ongoing work with this model and others should lead to a much better understanding of the relationship between climate and global hurricane activity.”

About the Rosenstiel School
Founded in the 1940's, the University of Miami's Rosenstiel School of Marine & Atmospheric Science has grown into one of the world's premier marine and atmospheric research institutions. Offering dynamic interdisciplinary academics, the Rosenstiel School is dedicated to helping communities to better understand the planet, participating in the establishment of environmental policies, and aiding in the improvement of society and quality of life.  For more information, please visit www.rsmas.miami.edu

Media Contacts:

Barbra Gonzalez
UM Rosenstiel School of Marine and Atmospheric Science
305.421.4704
barbgo@rsmas.miami.edu
Marie Guma-Diaz
UM Media Relations Office
305.284.1601
m.gumadiaz@umiami.edu