Is it fair to blame a single devastating storm like Katrina on global warming? "It's nonsense. It's statistical nonsense," says atmospheric scientist Kerry Emanuel. It's misguided to pinpoint global warming as the cause of specific storms. Yet both Emanuel and meteorologist Peter Webster and his team have gathered powerful evidence that rising sea surface temperatures have led, in general, to more intense storms over recent decades. Below, see what the scientists have to say and examine their data.—Susan K. Lewis
Note: Tropical cyclones are known around the world by different names—typhoons, hurricanes, cyclones. For simplicity, we refer here to all these storms as hurricanes.
Dr. Kerry Emanuel, MIT
Read the following excerpt from Kerry Emanuel's interview with NOVA scienceNOW. Then take a look at graphs he published in an August 2005 paper in Nature entitled "Increasing Destructiveness of Tropical Cyclones Over the Past 30 Years."
Emanuel: I was surprised. When I did this analysis in the Nature paper, I wasn't even looking for any kind of global trends. And global warming was far from my mind. I was looking for natural variability in the amount of energy expended by hurricanes. And you could see the natural variability, but on top of that, it's this trend that we couldn't really get rid of. It became worrying, and led to the Nature paper.
We find that in the Pacific, as well as in the Atlantic, there's this excellent correlation between this measure of hurricane energy that we developed and the temperature of the tropical ocean. It's very in concert on all kinds of different time scales. And the amount of energy expended by hurricanes has gone up in the last 50 years by somewhere between 50 and 80 percent.
If all we had to go on was the hurricane data, I don't think we would be terribly alarmed. We'd just say, well, it's been changing the last 25, 30 years, so what? It's the correlation with sea surface temperature and the fact that that trend is unprecedented for a long time that has us worried.
North Atlantic Storms
North Pacific Storms
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