July 31, 2005

Hurricane destructiveness increased over 30 years

By Patricia Reaney

LONDON (Reuters) - 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

"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 analyzed 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 8 hurricanes, according to a forecast.

"In theory, the peak wind speed of tropical cyclones should
increase by about 5 percent for every 1 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 39 miles per hour. Once the wind
speed gets to 74 miles 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