WASHINGTON — Top researchers now agree that the world is likely to get stronger but fewer hurricanes in the future because of global warming, seeming to settle a scientific debate on the subject.
But they say there's not enough evidence yet to tell whether that effect has already begun.
Since just before Hurricane Katrina hit Louisiana and Mississippi in 2005, dueling scientific papers have clashed about whether global warming is worsening hurricanes and will do so in the future. The new study seems to split the difference. A special World Meteorological Organization panel of 10 experts in both hurricanes and climate change — including leading scientists from both sides — came up with a consensus, which was published online Sunday in the journal Nature Geoscience.
"We've really come a long way in the last two years about our knowledge of the hurricane and climate issue," said study co-author Chris Landsea, a National Oceanic and Atmospheric Administration top hurricane researcher. The technical term for these storms are tropical cyclones; in the Atlantic they get called hurricanes, elsewhere typhoons.
The study offers projections for tropical cyclones worldwide by the end of this century, and some experts said the bad news outweighs the good. Overall strength of storms as measured in wind speed would rise by 2 to 11 percent, but there would be between 6 and 34 percent fewer storms in number. Essentially, there would be fewer weak and moderate storms and more of the big damaging ones, which also are projected to be stronger due to warming.
An 11 percent increase in wind speed translates to roughly a 60 percent increase in damage, said study co-author Kerry Emanuel, a professor of meteorology at MIT.
The storms also would carry more rain, another indicator of damage, said lead author Tom Knutson, a research meteorologist at NOAA.
Knutson said the new study, which looks at worldwide projections, doesn't make clear whether global warming will lead to more or less hurricane damage on balance. But he pointed to a study he co-authored last month that looked at just the Atlantic hurricane basin and predicted that global warming would trigger a 28 percent increase in damage near the United States despite fewer storms.
That study suggests category 4 and 5 Atlantic hurricanes — those with winds more than 130 mph — would nearly double by the end of the century. On average, a category 4 or stronger hurricane hits the United States about once every seven years, mostly in Florida or Texas. Recent category 4 or 5 storms include 2004's Charley and 1992's Andrew, but not Katrina which made landfall as a strong category 3.