Actually he doesn't. But Brad Plumer of the Washington Post's interesting Wonkblog cites political science research showing that voters do punish politicians for natural disasters that used to be called"acts of God."
Now, the evidence is somewhat mixed, for it can be hard to separate anger about events from anger about how the political officials respond to them, but the results are statistically significant, which is all you can ask for in poli-sci research.
One lesson for officials is that they have to be on tap and on top of responses to floods, tornadoes, and the like. I can think of several mayors who were on vacation in Florida when their cities were paralyzed by snowstorms and who then got the chance to take permanent vacations.
What the research doesn't show is how blame is likely to be assessed when global warming becomes undeniable and irreversible. I hope we all get smart before then.