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CLIMATE
CHANGE & ENVIRONMENT
Global warming may be contributing
to stronger hurricanes
Washington: 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..
-Sept
4, 2008
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