From NASA climatologist Gavin Schmidt, in the Washington Post, discussing the value of computer climate models:
If the models are as flawed as critics say, Schmidt said, "You have to ask yourself, 'How come they work?' "
Indeed. Also of note is a comment from someone who doesn't share Schmidt's confidence:
Warren Meyer, a mechanical and aerospace engineer by training who blogs at www.climate-skeptic.com, said that climate models are highly flawed. He said the scientists who build them don't know enough about solar cycles, ocean temperatures and other things that can nudge the earth's temperature up or down. He said that because models produce results that sound impressively exact, they can give off an air of infallibility.
Curiously, Meyer's lament about "impressively exact" model output appears just above a reference to the range of warming the IPCC says we can expect:
A 2007 United Nations report cited a range of estimates from 2 to 11.5 degrees over the next century.
Hmmm. Must be a use for the term "exact" with which I was not previously familiar.