Former Climate Skeptic Now Says Global Warming is Man-Made by Liz Goodwin Yahoo! News

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About-face: Former climate change skeptic now says global warming is man-made

By Liz Goodwin, Yahoo! News | The Lookout

National Affairs Reporter

He finally came around to what other climate scientists have been spouting for years. Richard A. Muller, a physics professor at the University of California-Berkeley, announced over the weekend that his much-publicized investigation into climate data has found that humans' production of carbon dioxide is causing the world to slowly warm up. And this process could speed up dramatically in the coming years.

Muller's conclusions attract special attention because of his vocal self-styling as a converted climate change skeptic. Muller criticized global warming studies for sloppy and self-serving data selection and a lack of transparency that obscured errors; he then lambasted fellow scientists for circling the wagons and calling any climate change deniers wrong. Muller says he's still upset that the American Physical Society declared the evidence for warming "incontrovertible" a few years ago in an official statement.

"We don't do things in science that are incontrovertible," Muller said in an interview with Yahoo News.

Muller took matters into his own hands and embarked on his own investigation into the data with his daughter Elizabeth and a team of scientists two years ago. His Berkeley Earth Surface Temperature project attracted funding from the Charles Koch Charitable Foundation, the nonprofit outfit of a wealthy businessman who denies that global warming is happening. Three years later, Muller ended up surprising himself when his research confirmed everything those same studies that drew his skepticism concluded, and then some. Muller says his study's results are more reliable than many previous ones because he intentionally avoided the data pitfalls he objected to, such as only using a portion of the global temperatures available. (He expounds on his methods here.)  Article is posted below.

Muller's study has not yet been published in a peer-reviewed scientific journal, but he says he plans to do so at some point. One climate scientist, Benjamin D. Santer, told the Los Angeles Times he thinks posting the study online and not in a journal is in "the spirit of publicity, not the spirit of science" and may do more to hurt the global warming cause than help it. But Muller wants to get feedback on his methods and to share his results with everyone, avoiding what he sees as a secrecy and lack of transparency that surrounded earlier climate change studies.

Though Muller is now entirely convinced that the Earth is warming due to man-made causes, he still expresses disdain for people who try to raise passions around the issue by pointing to local weather events, such as the drought scorching up America's Midwest right now, as proof of the phenomenon. (He attributes the drought to La Niña, a temporary cooling of the ocean.) The effects of global warming on local weather patterns are unknown, and even as two-thirds of the world has heated up, another one-third has shown a gradual cooling over the past 250 years, he says. The overall effect is a troubling global warming, but Muller has no patience for simplifications that stray from the truth.

"I'm personally very worried," he says of global warming. Muller says that so far the warming has been "tiny," but that everything points to the process speeding up. "I personally suspect that it will be bad."

Muller is now wading into another controversy, by endorsing the process of natural gas extraction called fracking for developing countries, which tend to rely more on coal. Coal production creates more carbon dioxide, but fracking has also drawn its share of environmentalist critics.

"I believe the only kind of action that is sustainable is that which is profitable, and fortunately we can do that," he says. "We can become much more energy efficient."

 

Op-Ed Contributor

The Conversion of a Climate-Change Skeptic

By RICHARD A. MULLER
Published: July 28, 2012

Berkeley, Calif.


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. In its 2007 report, the I.P.C.C. concluded only that most of the warming of the prior 50 years could be attributed to humans. It was possible, according to the I.P.C.C. consensus statement, that the warming before 1956 could be because of changes in solar activity, and that even a substantial part of the more recent warming could be natural.

Our Berkeley Earth approach used sophisticated statistical methods developed largely by our lead scientist, Robert Rohde, which allowed us to determine earth land temperature much further back in time. We carefully studied issues raised by skeptics: biases from urban heating (we duplicated our results using rural data alone), from data selection (prior groups selected fewer than 20 percent of the available temperature stations; we used virtually 100 percent), from poor station quality (we separately analyzed good stations and poor ones) and from human intervention and data adjustment (our work is completely automated and hands-off). In our papers we demonstrate that none of these potentially troublesome effects unduly biased our conclusions.

The historic temperature pattern we observed has abrupt dips that match the emissions of known explosive volcanic eruptions; the particulates from such events reflect sunlight, make for beautiful sunsets and cool the earth’s surface for a few years. There are small, rapid variations attributable to El Niño and other ocean currents such as the Gulf Stream; because of such oscillations, the “flattening” of the recent temperature rise that some people claim is not, in our view, statistically significant. What has caused the gradual but systematic rise of two and a half degrees? We tried fitting the shape to simple math functions (exponentials, polynomials), to solar activity and even to rising functions like world population. By far the best match was to the record of atmospheric carbon dioxide, measured from atmospheric samples and air trapped in polar ice.

Just as important, our record is long enough that we could search for the fingerprint of solar variability, based on the historical record of sunspots. That fingerprint is absent. Although the I.P.C.C. allowed for the possibility that variations in sunlight could have ended the “Little Ice Age,” a period of cooling from the 14th century to about 1850, our data argues strongly that the temperature rise of the past 250 years cannot be attributed to solar changes. This conclusion is, in retrospect, not too surprising; we’ve learned from satellite measurements that solar activity changes the brightness of the sun very little.

How definite is the attribution to humans? 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. Adding methane, a second greenhouse gas, to our analysis doesn’t change the results. Moreover, our analysis does not depend on large, complex global climate models, the huge computer programs that are notorious for their hidden assumptions and adjustable parameters. Our result is based simply on the close agreement between the shape of the observed temperature rise and the known greenhouse gas increase.

It’s a scientist’s duty to be properly skeptical. I still find that much, if not most, of what is attributed to climate change is speculative, exaggerated or just plain wrong. I’ve analyzed some of the most alarmist claims, and my skepticism about them hasn’t changed.

Hurricane Katrina cannot be attributed to global warming. The number of hurricanes hitting the United States has been going down, not up; likewise for intense tornadoes. Polar bears aren’t dying from receding ice, and the Himalayan glaciers aren’t going to melt by 2035. And it’s possible that we are currently no warmer than we were a thousand years ago, during the “Medieval Warm Period” or “Medieval Optimum,” an interval of warm conditions known from historical records and indirect evidence like tree rings. And the recent warm spell in the United States happens to be more than offset by cooling elsewhere in the world, so its link to “global” warming is weaker than tenuous.

The careful analysis by our team is laid out in five scientific papers now online at BerkeleyEarth.org. That site also shows our chart of temperature from 1753 to the present, with its clear fingerprint of volcanoes and carbon dioxide, but containing no component that matches solar activity. Four of our papers have undergone extensive scrutiny by the scientific community, and the newest, a paper with the analysis of the human component, is now posted, along with the data and computer programs used. Such transparency is the heart of the scientific method; if you find our conclusions implausible, tell us of any errors of data or analysis.

What about the future? As carbon dioxide emissions increase, the temperature should continue to rise. I expect the rate of warming to proceed at a steady pace, about one and a half degrees over land in the next 50 years, less if the oceans are included. But if China continues its rapid economic growth (it has averaged 10 percent per year over the last 20 years) and its vast use of coal (it typically adds one new gigawatt per month), then that same warming could take place in less than 20 years.

Science is that narrow realm of knowledge that, in principle, is universally accepted. I embarked on this analysis to answer questions that, to my mind, had not been answered. I hope that the Berkeley Earth analysis will help settle the scientific debate regarding global warming and its human causes. Then comes the difficult part: agreeing across the political and diplomatic spectrum about what can and should be done.

Richard A. Muller, a professor of physics at the University of California, Berkeley, and a former MacArthur Foundation fellow, is the author, most recently, of “Energy for Future Presidents: The Science Behind the Headlines.”


 A version of this op-ed appeared in print on July 30, 2012, on page A19 of the New York edition with the headline: The Conversion of a Climate-Change Skeptic.