High-profile former climate skeptic: “Humans are almost entirely the cause”
DOI: 10.1063/PT.4.0161
Articles in this venue and elsewhere last October discussed the highly public transformation of the climate views of Richard A. Muller, a physicist at the University of California, Berkeley. Consider now the opening of his 30 July New York Times op-ed ‘The Conversion of a Climate-Change Skeptic':
Call me a converted skeptic. 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.
My total turnaround, in such a short time, is the result of careful and objective analysis by the Berkeley Earth Surface Temperature project, which I founded with my daughter Elizabeth. Our results show that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half 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.
These findings are stronger than those of the Intergovernmental Panel on Climate Change, the United Nations group that defines the scientific and diplomatic consensus on global warming.
Muller declares that his group, using statistical methods, avoided biases often alleged to arise from urban heating, data selection, poor monitoring station quality, human intervention and data adjustment. And their analysis ‘argues strongly,’ he says, ‘that the temperature rise of the past 250 years cannot be attributed to solar changes.’ He asks, ‘How definite is the attribution to humans?’ And he answers:
The carbon dioxide curve gives a better match than anything else we’ve tried. Its magnitude is consistent with the calculated greenhouse effect — extra warming from trapped heat radiation. These facts don’t prove causality and they shouldn’t end skepticism, but they raise the bar: to be considered seriously, an alternative explanation must match the data at least as well as carbon dioxide does.
Concerning the attribution of specific weather events to climate change, Muller retains not just skepticism but disbelief. He stipulates, ‘I still find that much, if not most, of what is attributed to climate change is speculative, exaggerated or just plain wrong,’ adding, ‘I’ve analyzed some of the most alarmist claims, and my skepticism about them hasn’t changed.’ Hurricane Katrina, for example, ‘cannot be attributed to global warming.’ The recent heat wave is offset by cool weather elsewhere.
Muller notes that his group’s papers are online at BerkeleyEarth.org. Near the end he says he hopes that their ‘analysis will help settle the scientific debate regarding global warming and its human causes.’ He finishes with this: ‘Then comes the difficult part: agreeing across the political and diplomatic spectrum about what can and should be done.’
Steven T. Corneliussen, a media analyst for the American Institute of Physics, monitors three national newspapers, the weeklies Nature and Science, and occasionally other publications. He has published op-eds in the Washington Post and other newspapers, has written for NASA’s history program, and is a science writer at a particle-accelerator laboratory.