Katrina May Be A Harbinger Of Storms To Come, Science Author Says

Hurricane Katrina caused death and destruction unprecedented in U.S. history, but with rising sea temperatures possibly fueling more Category 4 and 5 hurricanes, the Gulf Coast and Eastern seaboard of the United States are at risk from more such storms in the future, says the author of a new study in Science.

Peter Webster, a top U.S. atmospheric scientist, led a team of researchers who report in the journal's 16 September issue that the number of high-intensity cyclones, typhoons and hurricanes has increased in all of the world's ocean basins since 1975. In the North Atlantic, including the Caribbean Sea and Gulf of Mexico, the number of Category 4 and 5 hurricanes has increased 56 percent, from 16 between 1975 and 1989 to 25 between 1990 and 2004.

In an interview, Webster cautioned that while the evidence indicates a link between rising sea surface temperatures and hurricane intensity, the evidence is not yet conclusive. And, he added, a single hurricane like Katrina is not by itself sufficient to validate the team's hypothesis. Still, he said, "Katrina has served as a wake-up call for developing improved risk assessments and management plans for the impacts of intense hurricanes.

"Storms like Katrina should not be regarded as a 'once-in-a-lifetime' event in the coming decades, but may become more frequent," he said. "This suggests that risk assessment is needed for all coastal cities in the southern and southeastern U.S. for category 5 storms, and for the more northern cities (e.g. New York City) probably for category 3 storms…. Past strategies for 'weathering the storm' will not work in the face of increased hurricane intensity."

The researchers reported a seeming paradox: The total number of hurricanes and hurricane days has decreased in every ocean basin except the North Atlantic, where the numbers have risen steadily since 1970. At the same time, however, the intensity of hurricanes is up in every basin. The Western Pacific Ocean had the most violent storms-a total of 116 Category 4 or 5 hurricanes between 1990 and 2004, up 36 percent from the 85 recorded between 1975 and 1989.

Webster holds joint appointments at Georgia Tech in the School of Earth and Atmospheric Sciences and the School of Civil and Environmental Engineering. Last year he received the prestigious Carl Gustaf Rossby Research Medal from the American Meteorological Society, the highest honor the society awards to atmospheric scientists. Webster is a fellow of the American Meteorological Society, the Royal Meteorological Society and the American Geophysical Union.

Also on the research team were Greg Holland, director of the division studying weather on the local and regional scale at the National Institute for Atmospheric Research in Boulder, Colo.; Judith A. Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech and a researcher studying climate and remote sensing; and Hai-Ru Chang, a senior research scientist at Georgia Tech's School of Earth and Atmospheric Sciences.

Because of the paper's timeliness for people affected by the disaster and for policy-makers, Science and AAAS are making it freely available online after 5:00 p.m. U.S. Eastern Standard Time on 15 September 2005. It also will be included in the collection of pertinent stories on climate, hurricanes and Katrina assembled by Science.

Webster discussed the new research this week in an email interview with AAAS Senior Writer Edward W. Lempinen. Read it here.

Edward W. Lempinen

15 September 2005

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