I guess we knew this but in case there was any doubt.......
Warmer ocean temperatures linked to hurricane intensity
Study adds to debate on effects of global warming.
By Mike Toner
ATLANTA JOURNAL-CONSTITUTION
Friday, March 17, 2006
ATLANTA — Rising ocean temperatures are directly linked to a worldwide increase in hurricane strength over the past 35 years, a research team reported Thursday — a finding that could add fuel to the debate over possible links between global climate change and hurricanes.
The analysis by researchers at Georgia Tech University expands on two studies last year that showed a pronounced global increase in the number of intense hurricanes — those ranked as Category 4 or 5 — since 1970.
Bill Feig
ASSOCIATED PRESS
(enlarge photo)
The havoc wreaked by Hurricane Katrina lingers more than six months later as boats jam up against a bridge in Empire, La. Though some disagree, Georgia Tech University researchers said increasing hurricane strength is directly related to the warming of the world's oceans.
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The new research stops short of blaming global warming but says the increase is "directly due" to higher sea surface temperatures, which are up about one degree in the past 35 years.
Higher ocean temperatures are one of several factors, including humidity, wind shear or broad air circulation patterns, that contribute to the formation of hurricanes, and the Georgia Tech study says the absence of any clear trend in the other factors leaves rising ocean temperatures as the only culprit.
"If you examine the intensification of a single storm, or even the statistics for a particular season, factors like wind shear can play a significant role," said Judith Curry, chairwoman of Georgia Tech's School of Earth and Atmospheric Sciences. "But there is no global trend in wind shear or other factors over the 35-year period. And there is a clear positive trend in sea surface temperature in each of the ocean basins we studied."
Climate experts and hurricane forecasters agree that higher ocean temperatures provide — in the form of increased water vapor — the fuel for hurricane intensification. Unusually warm waters in the Gulf of Mexico and the Caribbean Sea played a key role in stoking several of last year's hurricanes.
The Georgia Tech study, posted online Thursday by the journal Science, comes after several unusually disruptive storm seasons worldwide.
Hurricanes during the 2005 North Atlantic storm season set records not only for their severity but also for the number that made landfall, such as Hurricane Katrina, which killed more than 1,300 people in Louisiana and Mississippi. Last March, communities in southern Brazil suffered severe damage in the region's first recorded severe cyclone, as hurricanes are known outside of the Atlantic Ocean and Caribbean.
Meanwhile in the Pacific, 10 major tropical cyclones made landfall in Japan during 2004. Last year, five fully developed cyclones raged through the Cook Islands in a single five-week period.
Hurricane forecasters and global warming skeptics challenged the Georgia Tech team's original research, published last September shortly after Hurricane Katrina, because it appeared to link recent hurricane activity directly to global warming.
Hurricane forecasters say last year's record of 14 hurricanes and 27 tropical Atlantic cyclones merely reflects part of a well-known — and natural — 20- to 30-year cycle.
Curry and her Georgia Tech colleagues, Carlos Hoyos, Paula Agudelo and Peter Webster, acknowledge the cycle. But they contend that the recent increase in intense hurricanes is the result of the regular cycle "imposed on the long-term trend" of increasing sea surface temperatures. "We were not expecting to get caught up in the global warming debate when we published our initial research last September," Curry said. "But the whole question of global warming is something that has to be confronted."
Critics were happy to join the confrontation. University of Virginia professor Pat Michaels, a fellow of the Cato Institute, claims that the Georgia Tech researchers failed to consider that the last peak in the Atlantic hurricane cycle occurred when ocean waters were cooler.
"Careful scrutiny of all of the available data shows the connection to global warming is less than tenuous," he said.
Chris Landsea, science officer for the National Hurricane Center, praised the researchers for "careful" work, but warned that inconsistencies in the 35 years of worldwide data on hurricane intensity makes their conclusions shaky.
A panel of hurricane experts convened by the World Meteorological Organization in February to assess the effects of climate change formally concluded that no single severe tropical storm during the past two years can be "directly attributed to global warming."
A trend toward more severe storms may be emerging, the panelists said, but it was too soon to understand why.
"This is a hotly debated area for which we can provide no definitive conclusion," the panelists reported.
The new report comes on the heels of a warning this week by a coalition of state insurance commissioners that the insurance industry is "threat- ened by a perfect storm of rising weather losses, rising global temperatures and more Americans than ever living in harm's way."
The National Association of Insurance Commissioners warned that "more frequent and more powerful weather events" are posing huge challenges for the insurance industry, already reeling from back-to-back hurricane-related losses of $30 billion in 2004 and more than $60 billion last year.
The commissioners established a task force to study the issue. "It's becoming clearer that we are experiencing more frequent and more powerful weather events," said Tim Wagner, director of the Nebraska insurance department. "And the impacts are being felt on our coasts and in the interior of the United States — including drought, tornadoes, brush fires, and severe hailstorms."
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