Lots of people know about Asimov's Three Laws of Robotics. Most people don't know his other law, though, which states that in the time it takes a reasonable person to refute one of a pseudo-scientist's claims, the pseudo-scientist can make ten more. He was talking about Immanuel Velikovsky and Erich von Daniken (remember them?), but it applies just as strongly today to those people who still don't want global warming to be mankind's fault.
New Scientist magazine has therefore done us all a favor by putting together a list of myths about global climate change, with responses. It's cogent, clearly written, and up to date --- well worth reading.