Strength of tropical storms has increased: study

September 4th, 2008 - 2:15 pm ICT by IANS  

Washington/New York, Sep 4 (DPA) The strength of tropical cyclones - especially hurricanes in the Atlantic and typhoons in the northern Indian oceans - have increased over the last 25 years as sea temperatures have risen, according to a study published in the journal Nature Thursday.Researchers found that an increase in water temperature by 1 degree Celsius corresponded to a nearly one-third rise in the number of strong storms worldwide, from an average of 13 to 17 per year.

The strongest storms were getting stronger, with wind speeds from the most intense storms increasing from an average of 225 km per hour in 1981 to 251 km per hour in 2006, the study found. During that time period, global ocean temperatures in areas where the storms form increased from 28.2 degrees Celsius to 28.5 degrees.

The findings bolster a theory first put forward in 2005 that the increase in the intensity of storms was due to higher ocean temperatures attributed to global warming. The energy of storms comes partially from the waters over which they form, the theory says.

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

Scientists from Florida State University and the University of Wisconsin used data on storms dating back to 1981 to compare the maximum wind speeds developed by tropical storms during their life spans.

But the effect of sea temperatures was not the same everywhere, researchers cautioned, and other factors such as the life span of the storm, its distance from land and solar activity must also be considered.

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