The verdict is in: Global warming is real and greenhouse-gas emissions from human activity are the main cause.
This, according to Richard A. Muller, professor of physics at the University of California, Berkeley, a MacArthur fellow and co-founder of the Berkeley Earth Surface Temperature project.
The United Nations Intergovernmental Panel on Climate Change and hundreds of other climatologists around the world came to such conclusions years ago.
However, the difference now is the source: Muller is a longstanding, colourful critic of prevailing climate science, and the Berkeley project was heavily funded by the Charles Koch Charitable Foundation, which, along with its libertarian petrochemical billionaire founder Charles G Koch, has a considerable history of backing groups that deny climate change.
In an opinion piece in Saturday's New York Times titled The Conversion of a Climate-Change Skeptic, Muller writes: "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."
The Berkeley project's research has shown, Muller says, "that the average temperature of the earth's land has risen by 2 degrees Fahrenheit over the past 250 years, including an increase of 1 degrees Fahrenheit 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."
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.
Climate-change denier changes his mind