Global warming 'makes hurricanes stronger'

Hurricanes have become more destructive over the past 30 years and global warming could increase their intensity in the future, an expert warned on Sunday.

He found that both the duration of the tropical cyclones and the wind speeds they produce have risen by 50 percent along with increases in the average surface temperature of tropical oceans.

"My results suggest that future warming may lead to an upward trend in tropical cyclone destructive potential, and taking into account an increasing coastal population, a substantial increase in hurricane-related loss in the 21st century," Professor Kerry Emanuel of the Massachusetts Institute of Technology (MIT) in the United States said.

In a research letter published in the science journal Nature he analysed records of tropical cyclones - hurricanes and typhoons - since the middle of the 20th century.

His findings suggest that the rising sea surface temperature, thought to be due at least in part to global warming, is responsible for the increased power of hurricanes.

"I have shown that they have become more destructive over the last 30 years. This particular hurricane energy measure is very well correlated with the surface temperature of the tropical oceans. That temperature has an upward trend. It has increased by about half a degree Centigrade over the last 50 years," Emanuel explained in an interview.

Many climatologists believe the rise in sea surface temperature is a signal of global warming.

"We've concluded that the hurricanes may also be a reflection of that," he added.

Last year's hurricane season was one of the most devastating ever recorded. It caused billions of dollars of damage in the Caribbean and the United States and included 15 tropical storms - 9 of which grew into hurricanes.

The 2005 hurricane season is expected to have about 15 named storms including eight hurricanes, according to a forecast.

"In theory, the peak wind speed of tropical cyclones should increase by about five percent for every one degree Centigrade increase in tropical ocean temperature," Emanuel explained in the report.

A storm is upgraded to a tropical storm and is named when it has winds of more than 63km per hour. Once the wind speed gets to 119km per hour it is classified a hurricane.

Emanuel said research is needed to determine if there is a connection between hurricane intensity at sea and its destructiveness on land.

"If there is, it would imply that we should start to see more hurricane-induced losses over the next 50 years," he added.

Source: www.iol.co.za