September 25, 2013

Top scientists 95 percent certain of global warming

They are more certain global warming is real and man-made than that vitamins make you healthy, and are about as certain that cigarettes kill.

The Associated Press

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Smoke pours from a chimney at a cement plant in Binzhou city, in eastern China's Shandong province. Scientists from around the world have gathered in Stockholm for a meeting of a U.N. panel on climate change and will probably issue a report saying it is "extremely likely" that humans are mostly to blame for temperatures that have climbed since 1951.

AP

"What is understood does not violate any mechanism that we understand about cancer," while "statistics confirm what we know about cancer," said Cicerone, an atmospheric scientist. Add to that a "very high consensus" among scientists about the harm of tobacco, and it sounds similar to the case for climate change, he said.

But even the best study can be nitpicked because nothing is perfect, and that's the strategy of both tobacco defenders and climate deniers, said Stanton Glantz, a medicine professor at the University of California, San Francisco and director of its tobacco control research center.

George Washington's Gray said the 95 percent number the Intergovernmental Panel on Climate Change will probably adopt may not be realistic. In general, regardless of the field of research, experts tend to overestimate their confidence in their certainty, he said. Other experts said the 95 percent figure is too low.

Jeff Severinghaus, a geoscientist at the Scripps Institution of Oceanography, said that through the use of radioactive isotopes, scientists are more than 99 percent sure that much of the carbon in the air has human fingerprints on it. And because of basic physics, scientists are 99 percent certain that carbon traps heat in what is called the greenhouse effect.

But the role of nature and all sorts of other factors bring the number down to 95 percent when you want to say that the majority of the warming is human-caused, he said.

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