Tuesday, September 06, 2005

Just put your theories together and blow

Correlation does not equal causation, unless politics are involved—Is the intensity of Hurricane Katrina and the other serious storms of the last decade the result of global warming? Despite the political posturing—particularly of envirnonmentalists—the honest answer is, we don’t know. It most certainly could be, but the kind of data you need to make that conclusion doesn’t exist.

The theory goes this way. Hurricanes and storms like typhoons are generated over the ocean and the higher the temperature of the water, the more intense the storm is likely to become. Raise ocean temperatures two degrees and you have a storm on steroids. And, the ocean temperatures are rising, the result, almost every scientist believes, of global warming due to increased greenhouse gasses. Add to that the perceived increase in intensity of recent storms (Katrina comes after a summer of unusually high temperatures in the northern hemisphere) and you have the usual suspects.

The idea isn’t new. There is a long list of computer models showing this was certainly a possible conclusion. In 1998, researchers at NOAA in Princeton reported in Science that they used a “regional, high-resolution, hurricane prediction model” comparing 51 storms in the Pacific under present conditions with 51 storms in a world with higher CO2 concentrations. The result: more intense hurricanes. In 2001, NOAA scientists in Miami measured the number of Atlantic hurricanes between 1995 and 2000, and found that the overall activity doubled in that time compared to the previous 24 years. The increase was, they reported, the result of sea-surface temperature increases. “The present level of hurricane activity is likely to persist for an additional 10-24 years. The shift in climate calls for a reevaluation of preparedness and mitigation strategies." Good luck.

But the most important paper came in July in Nature on-line. MIT climatologist Kerry Emanuel concluded that the destructive power of hurricanes (duration and highest wind speeds) had increased 50% over the last half a century and that a rise in surface temperatures was likely to be at least part of the reason. He studied both typhoons in the Pacific and hurricanes in the Atlantic, essentially the same phenomenon. He doesn’t say it is the only reason; it could be just one variable, but it appears real.

NOAA data shows that hurricane activity has been higher than normal in nine of the last 11 years and it has forecast 21 tropical storms this season, which runs into late fall. That would make it one of the most dangerous hurricane seasons in history. Indeed.

On the other hand, hurricanes run in 20-30 year cycles and this could be just one of those up-cycles. It could also just be a statistical blip. It also is true that the data for most parts of the world is not complete and that would make analyses very difficult. The few remaining scientists who don’t believe in global warming (who of course must be quoted in every news story on global warming), scoff at all that, but they are in a lonely little world all their own. Emanuel’s research is the first to claim a link between global warming and hurricane intensity, and as they say in science, it needs more study. And funding. And we damned near better do it.

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