Ann Althouse makes a great point today with regard to a UK Guardian story entitled, "That snow outside is what global warming looks like," which has as its tendentious point that all that cold and snow in Britain this winter doesn't disprove global warming. Althouse says simply (and devastatingly) that "when everything is evidence of the thing you want to believe, it might be time to stop pretending you're all about science."
Althouse doesn't say it precisely, but what she's talking about is actually a fundamental premise in the philosophy of science (via Karl Popper), namely, that scientific fact has to be "falsifiable," i.e., there has to be some evidence that, if true, would make the theory false. If all evidence can be incorporated in the theory -- much like everything can be described as "God's will," or by the phrase "God works in mysterious ways," or "God can do anything" -- then you are not talking about science, but religion. If warmth is evidence of global warming, and cold is evidence of global warming -- or, in England, if no snow = global warming and snow = global warming -then global warming is not science anymore, it's a faith system. And, like any faith system, its arguments of late have often boiled down to demanding that heretics be silenced.
BTW, it's snowing here in Milwaukee. Here's a picture out my office window.... you can't quite see Lake Michigan: