Richard Muller is a professor of physics at the University of California, Berkeley. He is also the cofounder of the Berkeley Earth project. Richard Mueller was a skeptical researcher. He was especially skeptical about climate change, and even more so about human involvement if such climate existed.
Muller is apparently a good scientist. He did what scientists are supposed to do and tested the hypothesis... and he has discovered that all those climate scientists who had been saying for years that the Earth was warming, and that human activity was a prime cause... he discovered all those scientists were right.
"Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I'm now going a step further: Humans are almost entirely the cause."
Michael Mann of Penn State University in an interview with the Guardian said that he welcomed the Berkeley Earth project's results. Mueller's work validated what climate scientists have known with some degree of certainty for nearly two decades."
"I applaud Muller and his colleagues for acting as any good scientists would, following where their analyses led them, without regard for the possible political repercussions. They are certain to be attacked by the professional climate change denial crowd for their findings."
We can in part thank the Koch brothers (or Charles at least) for their funding of the research that lead to this about face.