For nearly 20 years climate change studies have carried the same message: The planet is heating up, the cause is atmosphere-clogging gases caused by human activity, and it's urgent to reverse the trend.

To all but an isolated few in the science world, it's a case-closed verdict. That's why it's significant that one of the few credentialed doubters is stepping forward to declare a "total turnaround" and profess belief in climate change.

UC Berkeley physics Professor Richard Muller says he's now "a converted skeptic" after conducting his own years-long research of rising temperature figures and weighing alternative explanations that include skewed data, solar changes, population growth and volcanic eruptions. None of it works as well as human-caused carbon dioxide emissions, he said.

There's an added feature to his about-face. A total of $150,000 of his research was paid for by the Koch Foundation, backed by two money-bags brothers in the oil business who don't accept climate change science.

Muller's change of mind comes with conditions. His findings need to be reviewed by his peers, an important check on his work. Also, his reversal has irked other scientists who endured his rough rebukes in the past.

But the message is still worth hearing. A once-devout denier, faced with the facts, now believes climate change is human-caused. Now comes the hard part, he said: "agreeing across the political and diplomatic spectrum about what can and should be done."