Actually Dyson seems to be hedging his bets on whether it is caused by man. He seems less convinced than the conventional view but accepts it could be the case. His main point is that it won't be so bad or could even be good.

The confusing part is why the global warming deniers would so instantly rush to him as verification of their views.

It is not exactly "confusing". The problem (as I see it) is that the question "does man cause Global Warming?" is ill-posed.

OK, let us say that we have a mathematical model of the global climate: a bunch of partial differential equations describing heat and mass flow, etc etc etc. Since humans burn fuels and release C02 on the atmosphere, it is obvious that man influences the weather. The real question is not "whether", but "how much". The Sun's cycles also influence the weather. Varying levels of cosmic radiation also influence the weather.

And if it's possible that the climate is indeed changing dramatically, what does "global warming" actually mean? The max temperatures are rising? Or does it mean that the average temperatures are rising? This is such a complex problem that interpreting it as a "yes / no question" is infuriating to say the least. Some people want to compress the entire global climate problem in one single bit of information. It's pathetic.

And what pisses me off is that there are hords of ignorants who believe this is a "religious war" against big oil and corporate America and claim that anyone who dissents is an heretic who was bought by the dirty capitalists and who should be burned at the stake.