This is a rather interesting statistical analysis. It was given as an assignment by an economics professor to his students. He asked for the cost of two scenarios being wrong: (i) that the climate change is predominantly due to human activities, and (ii) the climate change is not due to human activities.
The conclusion? Cost of being wrong with (ii) is a lot more devastating than the cost of (i) being wrong.
On a related note, the Drudge report tackles several misrepresentations of climate "evidence" that have been used by many to discredit the claim that global warming is due to human activities. In particular, the claim that Mars, Jupiter, and Pluto are also experiencing their own "global warming" due to the sun's activities are taken from an unverified comment, rather than scientific conclusion.