Wednesday, June 21, 2006

Gregg Easterbrook writes a Slate piece whose contention is that we should not blame global warming for increasing hurricane damage:
Bear in mind as well that chance is a significant factor in weather-related losses. Three major hurricanes, Eloise, Andrew, and Opal, hit Florida from 1965 to winter 2004. Since then, six—Charley, Frances, Ivan, Jeanne, Dennis, and Wilma—have battered the state. (Katrina was not a major hurricane when it crossed Florida.) Atlantic cyclone frequency and ferocity have increased somewhat since 1965. But the increase has been gradual: nothing like a jump from one major hurricane every 13 years to six in two years. Most likely, the recent escalation in major hurricanes that make landfall in Florida is due to bad luck following a long phase of good luck.
Easterbrook appears not to have done his homework. Research indicates that category 4 and 5 hurricanes have almost doubled over the last three decades. Moreoever, this increase is statistically significant for the North Atlantic (which is relevant to those of us in North America). Quoting from Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment,Science 16 September 2005:
...the North Atlantic Ocean, which possesses an increasing trend in frequency and duration [of hurricanes] that is significant at the 99% confidence level.
In other words, something is making more destructive hurricanes occur more often. It cannot be said with complete certainty that this is global warming at this point - not enough data is available for that. Nevertheless, chance does not explain the increase in more destructive hurricanes that have been hitting North America. This is not to deny that increasing property values have an influence on increasing property damage, but one cannot ignore, as Easterbrook does, the effect of more powerful hurricanes.


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