Washington - Climate change is affecting the intensity of Atlantic hurricanes, and hurricane damage likely will continue to increase because of greenhouse warming, according to a new study funded in part by the U.S. National Science Foundation.

The study shows for the first time a direct relationship between climate change and hurricane intensity, unlike other studies that have linked warmer oceans to a likely increase in the number of hurricanes, according to an August 15 press release from the American Geophysical Union (AGU). (See related article.)

James Elsner of Florida State University examined the statistical connection between the average global near-surface air temperature and Atlantic sea surface temperature, comparing the two factors with hurricane intensities over the past 50 years.

"The large increases in powerful hurricanes over the past several decades, together with the results presented here, certainly suggest cause for concern," Elsner said.

He found that average air temperatures during hurricane season between June and November are useful in predicting sea surface temperatures - a vital component in nourishing hurricane winds as they strengthen over warm waters - but sea surface temperatures are not useful in predicting air temperatures.

Several recent studies have warned that human-induced climate warming has the potential to increase the number of hurricanes, and previous research and computer models suggest that hurricane strength will intensify with increasing global mean temperatures.

Others hypothesize that the relationship between sea surface temperatures and hurricanes can be attributed to natural causes, such as the Atlantic Multidecadal Oscillation, an ongoing series of long-term changes in the sea surface temperature of the North Atlantic Ocean.

Using detailed data from the Intergovernmental Panel on Climate Change (IPCC) and the U.S. National Oceanographic and Atmospheric Administration to monitor sea temperature anomalies over the past half century, Elsner used a special test to establish evidence in support of the climate change/hurricane intensity hypothesis.

The World Meteorological Organization and the U.N. Environment Programme established the IPCC to assess scientific, technical and socioeconomic information relevant to the understanding of climate change, its impacts and options for adaptation and mitigation.

Elsner’s analysis helps verify a link between atmospheric warming caused largely by greenhouse gases and the recent upswing in frequency and intensity of Atlantic hurricanes, including Katrina and Rita, which devastated parts of Mississippi, Louisiana, and Texas in 2005.

"I infer that future hurricane hazard mitigation efforts should reflect that hurricane damage will continue to increase, in part, due to greenhouse warming," Elsner said.

Elsner said his research moves “the debate away from trend analyses of hurricane counts and toward a physical mechanism that can account for the various observations."

The text of the press release is available at the AGU Web site.