The Berkeley project’s research has shown, Muller says, “that the average temperature of the earth’s land has risen by 2½ degrees Fahrenheit over the past 250 years, including an increase of 1½ degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases.”
He calls his current stance “a total turnaround.”
Tonya Mullins, a spokeswoman for the Koch Foundation, said the support her foundation provided, along with others, has no bearing on results of the research.
“Our grants are designed to promote independent research; as such, recipients hold full control over their findings,” Mullins said in an email. “In this support, we strive to benefit society by promoting discovery and informing public policy.”
Some leading climate scientists said Muller’s comments show that the science is so strong that even those inclined to reject it cannot once they examine it carefully.
Michael E. Mann, director of the Earth System Science Center at Pennsylvania State University, said Muller’s conversion might help shape the thinking of the “reasonable middle” of the population “who are genuinely confused and have been honestly taken in” by attacks on climate science.
On his Facebook page, Mann wrote: “There is a certain ironic satisfaction in seeing a study funded by the Koch Brothers — the greatest funders of climate change denial and disinformation on the planet — demonstrate what scientists have known with some degree of confidence for nearly two decades: that the globe is indeed warming, and that this warming can only be explained by human-caused increases in greenhouse gas concentrations. 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.”