An Aug. 20 article incorrectly said that the Atlantic hurricane season runs from June 1 to Nov. 1. It runs from June 1 to Nov. 30.
Scientists Disagree On Link Between Storms, Warming
Sunday, August 20, 2006
A year after Hurricane Katrina and other major storms battered the U.S. coast, the question of whether hurricanes are becoming more destructive because of global warming has become perhaps the most hotly contested question in the scientific debate over climate change.
Academics have published a flurry of papers either supporting or debunking the idea that warmer temperatures linked to human activity are fueling more intense storms. The issue remains unresolved, but it has acquired a political potency that has made both sides heavily invested in the outcome.
Paradoxically, the calm hurricane season in the Atlantic so far this year has only intensified the argument.
Both sides are using identical data but coming up with conflicting conclusions. There are several reasons.
Using different time periods to chart hurricane patterns can influence the results. Different academic backgrounds also affect how researchers interpret the data. Climate scientists tend to test hypotheses and examine the underlying causes of climate variability over time, which makes them more comfortable identifying broad climate trends. Hurricane forecasters tend to be more focused on predicting the intensity and paths of individual storms, and often focus on factors such as wind shear and water temperature that can cause a storm to shift within a matter of days or hours, so they tend to emphasize natural variability over long-term climate shifts.
Inevitably, the scientific debate has spilled into the policy arena. Former vice president Al Gore took up the issue in his recent film "An Inconvenient Truth," suggesting that Katrina and other severe storms reflect a broader trend clearly traceable to global warming. Last week, environmentalist Lester Brown, president of the Earth Policy Institute, released a report that called the quarter of a million Katrina evacuees who will not return home "the world's first climate refugees."
On the other side, Myron Ebell, energy and global warming policy director at the Competitive Enterprise Institute, said these pronouncements amount to political opportunism. In contrast to activists who quickly attributed last year's hurricanes to climate change, he said, his side is not ready to claim victory just because this year has brought fewer intense storms.
"I don't think that says much one way or another about whether global warming causes hurricanes," said Ebell, whose group receives funding from the fossil-fuel industry.
Scientists who doubt a link with global warming say this year's average Atlantic hurricane season simply shows how variable weather can be. Christopher Landsea, who works in the National Oceanic and Atmospheric Administration's Hurricane Research Division, published an opinion piece in the journal Science late last month in which he argued that data indicating that recent hurricanes have been more intense than those in the 1970s and '80s may be based on flawed information. Measurement technologies were less sophisticated then and may have underestimated the strength of earlier storms, he said.
"We're woefully underestimating how strong hurricanes were back then," said Landsea, who wrote that five tropical cyclones that were originally classified as Category 3 would be rated as Category 4 today. "I'm sure it's confusing to the general public, since you have different scientists saying different things. We're all trying to figure out the same thing: What's going on with our climate?"
In contrast to the Atlantic, the Pacific is experiencing a much more active than usual storm season this year. Earlier this month, Typhoon Saomai, the strongest to hit China in half a century, crashed into the country's southeast coast and flattened tens of thousands of homes. It killed more than 300 people and prompted the evacuation of more than 1.5 million.
A number of factors might account for the fact that this year's Atlantic season, which runs from June 1 to Nov. 1, has so far produced far fewer named storms than last year's record-breaking season, and not a single hurricane. Sea surface temperatures are not as warm this year -- the ocean needs to be at least 79 degrees Fahrenheit to sustain a hurricane -- and the atmosphere is more stable because of clouds of Saharan dust that have swept across the Atlantic.