By Doyle Rice, USA TODAY
Could the USA deal with a Hurricane Katrina every two years?
Such a scenario is possible by the end of the century due to climate change, according to a study published Monday in the Proceedings of the National Academy of Sciences.
The frequency of extreme storm surges - the deadly and devastating walls of water that roar ashore during hurricanes - is projected to increase by as much as 10 times in coming decades because of warming temperatures, the study finds. Global warming has already doubled the chance of storms like Katrina, according to the study, which was led by climate scientist Aslak Grinsted of the University of Copenhagen in Denmark.
Storm surge is typically the biggest killer from hurricanes, and also usually causes the most destruction: Katrina killed more than 1,800 people and caused $125 billion in damage, mostly from storm surge, while Sandy last year killed dozens and caused at least $50 billion in damages.
Grinsted's research shows that there will be a tenfold increase in frequency of storm surges if the climate becomes 3.6 degrees Fahrenheit warmer. "This means that there will be a 'Katrina' magnitude storm surge every other year," he says.
One estimate from the Intergovernmental Panel on Climate Change shows that, under one of the "best-case" scenarios, Earth's atmosphere's temperature will rise anywhere from 2.0 to 5.2 degrees by the end of the century.
Grinsted says that a 0.7 degrees warming of the climate "corresponds to a doubling of the frequency of extreme storm surges like the one during Hurricane Katrina. With the global warming we have had during the 20th century, we have already crossed the threshold where more than half of all 'Katrinas' are due to global warming," he says.
This research used past storm surge data from six tidal gauges from the East and Gulf Coasts, all of which had information dating to the 1920s. The study also used this gauge data to look forward to the likelihood of future storm surges.
In addition to there being more extreme storm surges, the sea will also rise due to global warming, Grinsted says. As a result, the storm surges will become worse and potentially more destructive.
However, another expert finds fault with the study: "I find this paper to be very misleading," says Georgia Tech climatologist Judith Curry, who says they used "a very incomplete data set:" It only considers tide gauge measurements at six locations (Atlantic City, Charleston S.C., Mayport, Fla.; Pensacola, Fla.; Key West, and Galveston, Texas.)
"Their statistical projection is totally unconvincing, since it is based on a data set that incompletely represents U.S. landfalling hurricane activity since 1923," Curry says. Their data set is much inferior to other data sets, she says, such as the standard hurricane landfall data set maintained by the National Hurricane Center.
And while Curry admits that "it is likely that the maximum intensity of the strongest hurricanes would increase in a warmer climate, I do not currently place much confidence in climate model projections of future hurricane activity."