Storm severity, warming linked
Top scientists agree: Humans are likely making hurricanes worse.
By MEG LAUGHLIN
Published February 2, 2007
An international panel of top scientists declared Thursday for the first time that global warming is causing stronger hurricanes, such as Katrina.
The unanimous conclusion of the Intergovernmental Panel on Climate Change, comprising scientists from 113 countries, said global warming "more likely than not" causes hurricanes.
"It is very important that the language is so strong this time," Barbados scientist Leonard Fields said. Scientists agree that "more likely than not" means more than a 50 percent likelihood.
"What this also means is that people on the second floor of my building will be treading water by 2100," said Hugh Willoughby, earth science professor at Florida International University in Miami.
The report, which will be released today at the symposium in Paris, says that humans are responsible for global warming, which causes rising temperatures of land and sea, rising water levels, heat waves and worsening droughts. The rising sea temperatures cause more intense hurricanes, the panel said.
Jeff Masters, hurricane expert and founder of Weather Underground, an Internet weather information Web site, questioned the conclusions: "While there does seem to be a connection between global warming and hurricanes in the Atlantic, the fact that there is no firm evidence elsewhere makes us wonder."
Masters instead supports the findings of the World Meteorological Organization, which said in November that it could not link past strong hurricanes to global warming.
The scientists on this side of the debate say that the increase in the intensity of hurricanes is cyclical rather than the result of global warming. They cite water temperature records kept by steamship captains in the 19th century and computer models as part of the evidence that stronger hurricanes are part of a natural cycle rather than global warming.
"There's a lot of reason to believe the cycles are real," said FIU's Willoughby. "But I also believe global warming is real and having an effect on hurricanes in the Atlantic."
Willoughby said that while he doesn't "totally agree" with the Paris panel, he knows that it did not jump to conclusions. "It is made up of well-respected, mainstream scientists whose deliberations are ponderous," he said. "But a lot of the people who believe hurricanes are cyclical voted with their feet and didn't go to the conference."
Among those who refused to attend was Chris Landsea, hurricane researcher at the National Hurricane Center in Miami. In an "open letter to the community," Landsea wrote: "I have decided to withdraw from participating ... because I have come to view the part of the IPCC to which my expertise is relevant as having become politicized."
"No doubt about it. This is a very contentious subject and people will scream no matter what anyone says," said Massachusetts Institute of Technology professor Kerry Emanuel, whose study on global warming greatly influenced the Paris panel.
Because of his research on global warming, Time magazine recently named Emanuel as one of the 100 most influential people in the world.
Emanuel said that hurricanes and cyclones in the North Atlantic and North Pacific have gotten more powerful since the mid 1970s because of global warming. He bases this conclusion on research that shows increases in storm intensity since 1990 mirror increases in surface temperatures of tropical oceans.
"There just isn't much evidence that intense hurricanes are the result of cycles in nature," he told the St. Petersburg Times.
The panel, known for its cautious approach, agreed with him.
It first agreed that increased hurricane intensity is "most likely" caused by global warming, then further agreed that global warming is "very likely" caused by man-made burning of fossil fuels. "Very likely" means a more than 90 percent certainty.
On sea levels, the report projects rises of 7-23 inches by the end of the century. There could be an additional 3.9-7.8 inches if the recent surprising polar ice sheet melt continues. Some scientists believe even that's too conservative and that the sea level rise could be closer to 3-5 feet.
"What all of this scientific language means," Emanuel said, "is there are a lot of really good reasons to dump those Hummers."
Information from the Associated Press was used in this report.
[Last modified February 2, 2007, 02:08:35]
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