Storms of the Century 
by Andrew Kerr and David Terrasso
You may have already suspected it, but now even the scientific community agrees: hurricanes, typhoons, cyclones—whatever you choose to call them—are getting bigger. This from a recent Georgia Tech/National Atmospheric Research (NCAR) study out this month.
This year, tropical storms have made for the biggest news stories. We will be feeling the aftershocks of Katrina for years to come. In early October entire Guatemalan villages—and hundreds of people—disappeared under mud loosened by Hurricane Stan. But unlike some news media inventions, such as 2001's so-called "Summer of the Shark" (when shark attacks were actually lower than in previous years), researchers have confirmed that the increased ferocity and frequency of major hurricanes is for real.
Peter Webster, professor at Georgia Tech's School of Earth and Atmospheric Sciences, along with NCAR's Greg Holland and Tech's Judith Curry and Hai-Ru Chang, studied the number, duration and intensity of hurricanes (also known as typhoons or tropical cyclones) that have occurred worldwide from 1970 to 2004. The study was supported by the National Science Foundation (NSF).
"What we found was rather astonishing," said Webster. "In the 1970's, there was an average of about 10 Category 4 and 5 hurricanes per year globally. Since 1990, the number of Category 4 and 5 hurricanes has almost doubled, averaging 18 per year globally."
Category 4 hurricanes have sustained winds from 131 to 155 miles per hour; Category 5 systems, such as Hurricane Katrina at its peak over the Gulf of Mexico, feature winds of 156 mph or more.
"Category 4 and 5 storms are also making up a larger share of the total number of hurricanes," says Judith Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech and co-author of the study. "Category 4 and 5 hurricanes made up about 20 percent of all hurricanes in the 1970's, but over the last decade they account for about 35 percent of these storms."
It's almost as if multiple weaker storm systems like those seen in the past are joining forces to create more Category 4 and 5 monsters like Katrina.
It is not just the Gulf Coast that is suffering—and will continue to suffer—the ravages of bigger hurricanes. Sea surface temperatures have risen one half to one degree Fahrenheit across the globe, and consequently bigger storms are resulting in all regions where storm systems have been a regular occurrence.
If the results of the study seem disconcertingly familiar, it may be because you encountered an article in the September issue of
National Geographic reporting on similar findings. The journal
Nature published a study in July that focused on the North Atlantic and North Pacific storm systems and came to a similar conclusion. So, multiple studies, including Georgia Tech's, are confirming what some Gulf Coast residents have likely already been suspecting: today's hurricanes pack a greater punch than their predecessors. Unfortunately, that trend is likely to continue.
Some paragraphs in this article were taken from David Terrasso's piece "Hurricanes Are Getting Stronger, Study Says." Mr. Terrasso writes for Georgia Tech's Institute of Communications and Public Affairs.
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