More certainty on global warming

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An influential panel of climate scientists has expressed higher confidence than ever that human activity is the main cause of the rise in global temperatures since the 1950s, reports. A leaked draft of an upcoming report of the United Nations’ Intergovernmental Panel on Climate Change, based on a broad analysis of published scientific studies, concludes with 95 percent certainty that climate change is both real and man-made; the group’s 2007 report expressed only 90 percent certainty about that conclusion, up from 66 percent in 2001.

The panel’s stronger verdict comes despite a plateau in average global temperature over the past 15 years, which it attributes to a combination of factors, including natural weather variations, volcanic ash, and reduced heat from the sun during its latest 11-year cycle. The report warns that unless governments severely curtail greenhouse gas emissions, global temperatures could increase by as much as 9 degrees Fahrenheit by the end of the century.

“Emissions at or above current rates would induce changes in all components in the climate system,” the report says, “some of which would very likely be unprecedented in hundreds to thousands of years.”