Nate Silver considers the evidence:
It can't be said for certain that religion itself is the cause of these differences, because we haven't controlled for other sorts of variables. For instance, there is some tendency for Catholic countries to be concentrated in warmer-weather latitudes, where people might naturally have more reason to be concerned about planetary warming. Still, the differences generally seem to hold even within particular regions; in (Catholic) Ireland for instance, 66 percent believe global warming is the result of human activity, versus 48 percent for the (Protestant) United Kingdom.
(Image by Kawano Takeshi)