Muller on warming: "How much is due to varying solar activity and how much due to humans is a scientific issue that we're trying to address"

Scientists Often Pigeonholed By Political Debates : NPR

[Muller] Temperature has been rising over the last 100 years. That's pretty clear. How much is due to varying solar activity and how much due to humans is a scientific issue that we're trying to address.
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CONAN: You mentioned Anthony Watts. He runs a website for climate deniers
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CONAN: Urgency, though, is the critical word here, is it not?

Prof. MULLER: Well, I think one of the things we're trying to do at Berkeley Earth is determine how urgent it is. The global warming attributed by the IPCC, the big U.N. Council that makes this consensus report, attributes about half a degree, half a degree Celsius of warming to humans. But is it .4? Is it .3? If so, we have a lot more time. Is it .6 or.7? If so, we're in a big rush.