Global warming may be contributing to stronger hurricanes

Washington, September 4 : A new study has bolstered the theory that global warming may be contributing to stronger hurricanes in the Atlantic.

The study was carried out by FSU (Florida state University) geography Professor James B. Elsner, University of Wisconsin-Madison Professor James P. Kossin and FSU postdoctoral researcher Thomas H. Jagger.

It found out that the strongest tropical cyclones are, in fact, getting stronger - and that ocean temperatures play a role in driving this trend.

This is consistent with the "heat-engine" theory of cyclone intensity.

"As seas warm, the ocean has more energy that can be converted to tropical cyclone wind," Elsner said. "Our results do not prove the heat-engine theory. We just show that the data are quite consistent with it," he added.

Elsner's team looked at a subset of hurricanes that are closest to their maximum possible intensity (MPI).

Under the heat-engine theory, every storm will lose some energy through inefficiency, and that loss will limit the storm's potential. The MPI represents the storm's maximum potential under ideal environmental conditions.

"We speculated that you might not see a trend in the intensity of typical hurricanes due to environmental factors, but if the heat-engine theory is correct, you should see a trend in the intensity of hurricanes at or near their MPI," Elsner said. "On average, the strongest storms are closest to their MPI," he added.

The researchers created a data set from satellite observations of hurricane intensity of all tropical cyclones around the globe and looked at the maximum wind speeds for each one during a 25-year period.

Tropical cyclones, which include hurricanes, typhoons and tropical storms, occur on average about 90 times per year worldwide.

The researchers found that the strongest tropical cyclones are getting stronger, particularly over the North Atlantic and Indian oceans.

Wind speeds for the strongest tropical storms increased from an average of 140 mph in 1981 to 156 mph in 2006, while the ocean temperature, averaged globally over the all regions where tropical cyclones form, increased from 28.2 degrees Celsius to 28.5 degrees Celsius during this period.

"By creating a better, more consistent historical data set, we've been able to weed out quality issues that introduce a lot of uncertainty," Kossin said.

"Then, by looking only at the strongest tropical cyclones, where the relationship between storms and climate is most pronounced, we are able to observe the increasing trends in storm intensity that both the theory and models say should be there," he added.

ANI