Sunday, October 02, 2005

More Hurricanes? No

I covered James Glassman's analysis of historical hurricane activity here on August 31.
Giant hurricanes are rare, but they are not new. And they are not increasing. To the contrary. Just go to the website of the National Hurricane Center and check out a table that lists hurricanes by category and decade [when they hit the US mainland]. The peak for major hurricanes (categories 3,4,5) came in the decades of the 1930s, 1940s and 1950s, when such storms averaged 9 per decade. In the 1960s, there were 6 such storms; in the 1970s, 4; in the 1980s, 5; in the 1990s, 5; and for 2001-04, there were 3. Category 4 and 5 storms were also more prevalent in the past than they are now. As for Category 5 storms, there have been only three since the 1850s: in the decades of the 1930s, 1960s and 1990s.
I made a chart of that data. Of course the current decade - which has no name yet, let's call it the 00s - is not yet half over. So I projected the data for it. Click on the chart to enlarge it. (Sorry it's not more legible - a hurried effort in Excel and Fireworks.) It is clear that the decades of the 70s, 80s and 90s has less strong hurricanes than usual. The 00s so far are on the higher side, but not any new extreme. So the number of strong hurricanes does not provide evidence that human activity has made the globe warmer.

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