“Models show a 2- to 4-degree temperature increase by the end of the 21st century, and hurricanes will get about 4 percent stronger for every 2-degree increase,” he said, citing Princeton’s Geophysical Fluid Dynamic Laboratory and Tom Knutson for the research in this area.
In other words, the 1-degree water temperature increase off the coast of Africa could fuel a Category 3 hurricane at landfall, like Katrina, with 130-mph winds, to increase by about 2 percent. Two or three miles per hour of Katrina’s winds could have been the result of global warming, Mr. Landsea said.
“One or 2 percent stronger? That is a very tiny change today, and even in 100 years from now, it is very small,” he said.
Offset in Pacific
At Colorado State University, Phil Klotzbach wrote a rebuttal, published in the Geophysical Research Letter last week, to the Georgia Tech and MIT papers, and concluded that where sea-surface temperature has increased, there is in fact a slight decrease in hurricane activity.
“With regards to the number of Category 4-5 hurricanes, there has been a large increase in North Atlantic storms and a large decrease in Northeast Pacific storms,” wrote Mr. Klotzbach in “talking points” for the paper on his Web site. “When these two regions are summed together, there has been virtually no increase in Category 4-5 hurricanes.”
Like Mr. Landsea, Mr. Klotzbach attributes the Georgia Tech findings to bad data. Ms. Curry of Georgia Tech says that while there have been inconsistencies in processing the data over time and in different regions, no one has demonstrated that there is actually a major problem with the data itself.
“The key issue is whether you can distinguish a Category 4 from a Category 1 hurricane from satellite [data], the answer is almost always yes,” she said.
Clearly, it is a busy period for the number and intensity of academic research papers being published on global warming and hurricanes, but Mr. Landsea said all remains collegial in the meteorological community.
“These are my friends and colleagues. The disagreements are civil. This debate is essence of science that is alive. Everyone here is doing science. This debate is confusing for us. I’m sure it is confusing for everyone else,” said Mr. Landsea.
Mr. Emanuel said that for all practical purposes, the real problem of hurricanes is not number and intensity, but demographics and the desire of people to live by the sea.
If a hurricane blows itself out over the ocean or hits an unpopulated area, there are few consequences to life or property. However, if a major hurricane hits a populated area, like New Orleans, Miami or the Outer Banks of North Carolina, it can be catastrophic.
“By regulating insurance, by holding insurance rates down, we are subsidizing risky behavior. We are underwriting the drive to [build and populate] the coastline. That is the big hurricane problem in the United States,” he said.