Hurricanes Growing Stronger, Study Says
- Hurricanes Growing Stronger, Study Says
Global Warming May Be The Reason For Storms' Power
Wisconsin State Journal :: FRONT :: A3
Monday, August 1, 2005
Joseph B. Verrengia Associated Press
Is global warming making hurricanes more ferocious? New research
suggests the answer is yes.
Scientists call the findings both surprising and "alarming" because
they suggest global warming is influencing storms now -- rather than
in the distant future.
However, the research doesn't suggest global warming is generating
more hurricanes and typhoons.
The analysis by climatologist Kerry Emanuel of the Massachusetts
Institute of Technology shows for the first time that major storms
spinning in both the Atlantic and the Pacific since the 1970s have
increased in duration and intensity by about 50 percent.
These trends are closely linked to increases in the average
temperatures of the ocean surface and correspond to increases in
global average atmospheric temperatures during the same period.
"When I look at these results at face value, they are rather
alarming," said research meteorologist Tom Knutson. "These are very
Knutson, who wasn't involved in the study, works in the National
Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics
Laboratory in Princeton, N.J.
Emanuel reached his conclusions by analyzing data collected from
actual storms rather than using computer models to predict future
Before this study, most researchers believed global warming's
contribution to powerful hurricanes was too slight to accurately
measure. Most forecasts don't have climate change making a real
difference in tropical storms until 2050 or later.
But some scientists questioned Emanuel's methods. For example, the
MIT researcher did not consider wind speed information from some
powerful storms in the 1950s and 1960s because the details of those
storms are inconsistent.
Researchers are using new methods to analyze those storms and others
going back as far as 1851. If early storms turn out to be more
powerful than originally thought, Emmanuel's findings on global
warming's influence on recent tropical storms might not hold up, they
"I'm not convinced that it's happening," said Christopher W. Landsea,
another research meteorologist with NOAA, who works at a different
lab, the Atlantic Oceanographic & Meteorological Laboratory in Miami.
Landsea is a director of the historical hurricane reanalysis. "His
conclusions are contingent on a very large bias removal that is large
or larger than the global warming signal itself," Landsea said.
Theories and computer simulations indicate that global warming should
generate an increase in storm intensity, in part because warmer
temperatures would heat up the surface of the oceans. Especially in
the Atlantic and Caribbean basins, pools of warming seawater provide
energy for storms as they swirl and grow over the open oceans.
Emanuel analyzed records of storm measurements made by aircraft and
satellites since the 1950s. He found the amount of energy released in
these storms in both the North Atlantic and the North Pacific oceans
has increased, especially since the mid-1970s.
This year marked the first time on record that the Atlantic spawned
four named storms by early July, as well as the earliest category 4
storm on record. Hurricanes are ranked on an intensity scale of 1 to
In the past decade, the southeastern United States and the Caribbean
basin have been pummeled by the most active hurricane cycle on
record. Forecasters expect the stormy trend to continue for an
additional 20 years or more.
Even without global warming, hurricane cycles tend to be a
consequence of natural salinity and temperature changes in the
Atlantic's deep current circulation that shift back and forth every
40 to 60 years.
Since the 1970s, hurricanes have caused more property damage and
casualties. Researchers disagree over whether this destructiveness is
a consequence of the storms' growing intensity or the population boom
along vulnerable coastlines.
"The damage and casualties produced by more intense storms could
increase considerably in the future," Emanuel said.