The head of the U.S. delegation to a key global warming conference called its new report Friday "significant" and "valuable" to policy makers.
Sharon Hays, associate director of the Office of Science and Technology Policy at the White House, welcomed the strong language of the report, which said global warming is "very likely" manmade.
"It's a significant report. It will be valuable to policy makers," she told The Associated Press in an interview in Paris, where hundreds of scientists and government officials were meeting to discuss global warming.
Hays stopped short of saying whether or how the report could bring about change in U.S. President George W. Bush's policy about greenhouse gas emissions.
Delegates said it was a U.S. government scientist who helped push through the strong language in the report - an agreement by officials from 113 governments, including the United States - which is very different from the 1997 Kyoto Protocol that Bush has long opposed.
"I think it's hard to take the U.S. action on this as a signal of them changing policy," said John Reilly, associate director of research at the Massachusetts Institute of Technology's Joint Program on the Science and Policy of Global Change.
The report by the Intergovernmental Panel on Climate Change is a science document describing what scientists say is now happening and forecasting what will happen.
The report recommends no actions to slow global warming.
The 10-year-old Kyoto Protocol, which called for cuts in greenhouse gas emissions, is about reducing fossil fuel use to fight global warming. (The administration of U.S. President Bill Clinton agreed to it but did not push for U.S. Senate ratification after clear signals it would be rejected.)
The new report says global warming has begun, is "very likely" caused by man, and will be unstoppable for centuries, according to a copy obtained early Friday by The Associated Press.
The wording was largely the result of the leadership of U.S. government scientist Susan Solomon, who heads the panel's working group, several delegates said Thursday.
But Reilly noted that "saying that climate change is almost certainly occurring and it's almost certainly due to human activity is different than saying the impact of climate change is so bad that we need to do something right away."
Reilly, who represented the U.S. Department of Agriculture at IPCC negotiations in 1990 and 1995, said scientists such as Solomon are rarely told what to do by governments, including this administration. It is different for government officials, the AP says.
However, other nations' delegates noticed a slight change in the official U.S. government delegation to the climate panel between 2001 and now. One non-U.S. delegate, who asked not to be named so as to not cause a diplomatic stir, said this time "the U.S. is very much more constructive."
Bush's science adviser John Marburger - Hays' boss - said the president and his administration have long recognized that global warming is manmade and real.