Climate change skeptic now a believer

The Toronto Star:

A prominent climate change skeptic’s about-face on the subject is causing a stir in the world of environmental science.

In a self-proclaimed “total turnaround,” Richard A. Muller, a physics professor at the University of California, Berkeley, now says human greenhouse gas emissions are almost entirely to blame for global warming.

“Call me a converted skeptic,” Muller wrote in a July 28 New York Times op-ed. Three years ago, he said, he doubted whether global warming even existed. “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.”

While many scientific organizations reached that conclusion years ago, it’s one Muller wasn’t comfortable reaching until now, he told the Star.

“If that classifies me as a skeptic, I consider that proper skepticism; something that’s a duty for any scientist.”

Muller’s opinion is based on the Berkeley Earth Surface Temperature project, which he co-founded. Its results show the average temperature of the Earth’s land has risen by 1.5 C over the past 250 years.

The match between the temperature records and carbon dioxide records suggests human greenhouse gas emissions are the best explanation for the warming, the study says.

Muller says the findings are stronger than those from the latest UN Intergovernmental Panel on Climate Change report in 2007.

The project’s results are “elegantly simple,” Muller said. It rules out changes in solar activity in global warming and shows that volcanic eruptions have short-term, but not long-term, effects on global temperatures.

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