Richard Muller never changed his opinion on Global warming he only disagreed with some of the global warming alarmist when they were proven to hide the data. That was over the hockey stick scam.
Right, he was always skeptical of the hysteria, and he did say that scientists exaggerate things because that's the only way to get the population to DO SOMETHING. But in his lectures, he always properly said the AGW line, with some caveats. I actually respected him for that, I mean, come on, the guy teaches at Berkley, so for him, that was probably deeps skepticism.