In the strongest language it has ever used, a United Nations panel says global warming is "very likely" caused by human activities and has become a runaway train that cannot be stopped.
The warming of Earth and increases in sea levels "would continue for centuries ... even if greenhouse gas concentrations were to be stabilized," according to a 20-page summary of the report that was leaked to wire services.
The summary of the fourth report by the U.N.'s Intergovernmental Panel on Climate Change, or IPCC, was scheduled for release this morning in Paris. But scientists involved in the final editing process have been leaking bits and pieces from it all week, culminating in the leaking of the full report eight hours before its release.
The phrase "very likely" indicates a 90% certainty. The last IPCC report, issued five years ago, said it was "likely" that human activity was at fault, indicating a certainty of 66%.
Many scientists had argued during the editing process that the report should say it is "virtually certain" that human activities are causing global warming. That would indicate a 99% certainty.
But the change was strongly resisted by China, among other nations, because of its reliance on fossil fuels to help build its economy.
The report also says scientists' "best estimate" is that temperatures will rise 3.2 to 7.8 degrees by 2100. In contrast, the increase from 1901 to 2005 was 1.2 degrees.
The report also projects that sea levels could rise by 7 to 23 inches by the end of the century, and perhaps an additional 4 to 8 inches if the recent melting of the Greenland ice sheet and the Larsen B ice shelf in western Antarctica continues at current rates.
That is a decrease from the maximum of 35 inches predicted in the earlier study.
Nonetheless, such an increase would inundate many low-lying areas around the world, including islands such as Kiribati in the western Pacific Ocean and marsh areas near New Orleans. Such flooding would affect more than 10 million people.
The report also predicts a melting of Arctic ice during summers and a slowing of the Gulf Stream.
In addition, the report says, for the first time, that it is "more likely than not" that the strong hurricanes and cyclones observed since 1970 have been produced by global warming. The 2002 report said scientists did not yet have enough evidence to make such a link.
