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| Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
NEWS RELEASE: 2008-242 December 19, 2008
NASA Study Links Severe Storm Increases, Global Warming
In a presentation today to the fall meeting of the American Geophysical Union in
For every degree Centigrade (1.8 degrees Fahrenheit) increase in average ocean surface temperature, the team observed a 45-percent increase in the frequency of the very high clouds. At the present rate of global warming of 0.13 degrees Celsius (0.23 degrees Fahrenheit) per decade, the team inferred the frequency of these storms can be expected to increase by six percent per decade.
Climate modelers have long speculated that the frequency and intensity of severe storms may or may not increase with global warming. Aumann said results of the study will help improve their models.
"Clouds and rain have been the weakest link in climate prediction," said Aumann. "The interaction between the daytime warming of the sea surface under clear-sky conditions and increases in the formation of low clouds, high clouds and, ultimately, rain is very complicated. The high clouds in our observations—typically at altitudes of 20 kilometers (12 miles) and higher—present the greatest difficulties for current climate models, which aren't able to resolve cloud structures smaller than about 250 kilometers (155 miles) in size."
Aumann said the results of his study, published recently in Geophysical Research Letters, are consistent with another NASA-funded study by Frank Wentz and colleagues in 2005. That study found an increase in the global rain rate of 1.5 percent per decade over 18 years, a value that is about five times higher than the value estimated by climate models that were used in the 2007 report of the Intergovernmental Panel on Climate Change.
JPL manages the AIRS project for NASA's Science Mission Directorate, Washington. For more information on AIRS, visit http://airs.jpl.nasa.gov/ .
JPL is managed for NASA by the California Institute of Technology in