Answer: Pretty stupid.
The issue is whether or not global warming is leading to increases in ocean temperatures, which leads to more ferocious hurricanes.
I acknowledge that the scientific jury is still out on this issue, but Jonah’s explanation why it is not so is — well — stupid. Pointing to this NOAA chart, he writes:
We are almost done with 2005. The average number of major (cat 3, 4 or 5) hurricane strikes on the US per decade is 6. There were 10 during the 1940s.
And by gosh, he’s right. If you look at the NOAA chart, the number of Category 3, 4, or 5 hurricanes from 1941-1950 is indeed listed as 10. And the average per decade is listed as 6.
A couple of problems, though.
First of all, the chart shows only hurricanes to strike the U.S. mainland! A category 5 hurricane which weakens to a Category 2 hurricane by the time it hits the U.S. mainland gets listed as a Category 2, not a Category 5. And a Category 5 hurricane that hits Mexico mainland, doesn’t get listed at all!
In fact, "hurricanes to strike the U.S. mainland" is a bad indicator of the overall the quantity and ferocity of hurricanes worldwide. It’s like me saying, "There were fewer car accidents at the corner of Main and First Street this year, therefore, traffic accidents citywide are decreasing in number."
Jonah tacitly acknowledges this problem, when he writes:
If global warming explained the current spate of big hurricanes, there would be more in the South Pacific and elsewhere. It’s my understanding there haven’t been.
Wow. It’s his "understanding". Thanks for the factual support.
Secondly, the chart shows that there were three Cat 3/4/5 hurricanes from 2001-2004. So obviously, it does not include Katrina or Rita (FLASH UPDATE: Hurricane Rita is now a Category 5 hurricane). So, if the "average per decade is 6", we have already reached 5 in this decade, which is only half over! In other words, his "chart" (even assuming the data was relevant to worldwide hurricanes) shows that this is one of the worst decades for serious hurricanes in recorded history. How exactly does this disprove global warming?
UPDATE: More Jonah stupidity here.