Submitted by Mark Goldes (Overtone): Study Ties Warming to Intense Hurricanes
- By RANDOLPH E. SCHMID, AP Science Writer/ Monday, September 11, 2006
(09-11) 15:44 PDT WASHINGTON, (AP) --
Most of the increase in ocean temperature that feeds more
intense hurricanes is a result of human-induced global warming, says a
study that one researcher says "closes the loop" between climate change
and powerful storms like Katrina.
A series of studies over the past year or so have shown an increase
in the power of hurricanes in the Atlantic and Pacific oceans, a
strengthening that storm experts say is tied to rising sea-surface
temperatures.
And most of that temperature increase can be blamed on global
warming caused by human activities such as automobile and industrial
pollution, scientists report in Wednesday's issue of Proceedings of the
National Academy of Sciences.
"The work that we've done kind of closes the loop here," said
Tom Wigley of the National Center for Atmospheric Research in Boulder,
Colo., a co-author of the paper.
"The important conclusion is that the observed (sea-surface
temperature) increases in these hurricane breeding grounds cannot be
explained by natural processes alone," said Wigley. "The best
explanation for these changes has to include a large human influence."
Benjamin Santer of Lawrence Livermore National Laboratory,
Livermore, Calif., plus Wigley and their team studied the relationship
of climate and hurricanes using 22 different climate models at 15
institutions around the world.
Climate models are complex sets of mathematical equations
that high-speed computers use to simulate weather and climate and to
forecast changes. The researchers used them to run 80 different
simulations analyzing the response of sea-surface temperatures to a
variety of factors and then compared the results from the independent
models.
While previous studies have looked at entire oceans, this
work focused on the smaller areas of the Atlantic and Pacific where
tropical storms form.
This study builds a connection between the theoretical
foundation of global warming and changes that are being observed in
those areas where hurricanes are born, said Robert Corell of the
American Meteorological Society, who moderated a briefing on the work.
While they reported the connection between rising ocean
temperatures and increasing storm power, the researchers declined to
predict future changes.
Asked if they would recommend changes in public policy, Greg
Holland of the National Center for Atmospheric Research said, "It is
important to note that we're not policymakers. Our role is to present
the best possible conclusions from the available evidence."
Kerry Emanuel, a hurricane expert at Massachusetts Institute
of Technology, added that regardless of global warming, the United
States does need to address problems in dealing with hurricanes ranging
from insurance to disaster response.
Not so sure of the findings was William M. Gray of Colorado
State University, a longtime hurricane expert who issues forecasts each
year of the expected number of storms.
Gray said the models do not deal with all necessary ocean
processes and called the report "a desperate attempt to keep the
bandwagon going. They've kept it going with global warming and now they
want to keep it going with hurricanes."
"I am very sure over the test of time it will not hold up," said Gray, who was not part of the research team.
Philip Klotzbach, also of Colorado State, said that
"sea-surface temperatures have certainly warmed over the past century,
and that there is probably a human-induced component.
"To me, the big challenge is still determining what
percentage is natural and what percentage is caused by humans. This
paper sheds some light on that question; however, there is still a
considerable amount of uncertainty," he said.
Christopher Landsea, a meteorologist at the National Oceanic
and Atmospheric Administration's Hurricane Research Division in Miami,
praised the new paper as very well thought out.
But, he said, while the paper discusses sea-surface
temperature increases, it does not address the sensitivity of
hurricanes to ocean temperature changes or questions about hurricane
records in prior years.
While studies by Emanuel in Nature and Peter J. Webster of
the Georgia Institute of Technology in Science reported increases in
the most powerful storms, Klotzbach challenged those findings in
Geophysical Research Letters, reporting only a small increase and
suggesting that may be due to improved observation technology.
Santer's research was funded by the Department of Energy.
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URL: http://sfgate.com/cgi-bin/article.cgi?file=/n/a/2006/09/11/national/w143819D74.DTL