Climate Scientist Eric Steig's reaction to the announcement that former climate skeptic Richard Muller recently confirmed that the earth is in fact warming is perhaps best captured by this classic XKCD comic.
As Steig put it at RealClimate:
As far as the basic science goes, the results could not have been less surprising if the press release had said “Man Finds Sun Rises At Dawn.”
Muller says that “the biggest surprise was that the new results agreed so closely with the warming values published previously by other teams in the U.S. and the U.K..” We find this very statement surprising. As we showed two years ago, any of various simple statistical analyses of the freely available data at the time showed that it was very very unlikely that the results would change.
Schmidt's larger point is not that Muller is dumb — he's an accomplished physicist and appears to have done incredibly careful work. It's that the science of global warming derives from physical principles so basic that a high school algebra student can solve their equations.
In other words, physicists know the earth is warming because it takes only an incredibly simple model to illustrate that this must be so — all the subsequent evidence that this is in fact happening is merely an exploration of scale, speed, and other details.
As a physicist, Muller knows that the reason for concern about increasing CO2 comes from the basic physics and chemistry, which was elucidated long before the warming trend was actually observable.