A UN panel of scientists and national delegations has agreed on an "instant guide" for policy makers, declaring unequivocally that climate change has begun and threatens to irreversibly alter the planet.
The document, to be published Saturday, summarizes the scientific consensus on human-induced climate change. It will be the first point of reference for delegates at a crucial meeting in Indonesia next month that is intended to launch a political process on international cooperation to control global warming.
Negotiators from more than 140 countries wrangled for five days until dawn Friday before approving a 20-page summary of data and computer projections. Then they labored throughout the day to finalize a longer 70-page version. Both papers synthesize research compiled over the last six years by the Nobel-winning Intergovernmental Panel on Climate Change.
UN Secretary-General Ban Ki-moon will address the IPCC when it releases the report Saturday.
"It's done. They have come up with a really strong report," said Hans Verholme, of the World Wide Fund for Nature.
The papers describe how climate systems are changing and why, the impacts it is having on mankind and ecosystems, and various scenarios of future impacts, depending on how quickly action is taken to slow the trend.
Another WWF climate scientist, Stephan Singer, called it a "groundbreaking document that will pave the way for deep emissions cuts by developing countries."
The report does not commit participating governments to any course of action but it is important because it is adopted by consensus, meaning those countries accept the underlying science and cannot disavow its conclusions. It provides a common scientific base line for the political talks.
"Warming of the climate system is unequivocal," the summary begins, in a statement meant to dispel any skepticism about the reality of climate change, said participants in the meeting.
In a startling and much-debated conclusion, the document warns that human activity risks causing "abrupt or irreversible changes" on Earth, including the widespread extinction of species and a dramatic rise in sea levels before the end of this century, they said on condition of anonymity because the details are supposed to remain confidential until Saturday.
"I think overall it is a good and balanced document," said Bert Metz, an eminent Dutch scientist and one of the 40 authors of the draft. "In the end, a lot of people had to compromise," he said.
Though it contains no previously unpublished material, the summary pulls together the central elements of three lengthy reports the IPCC released earlier this year. Boiling down the 3,000 pages into about 20 was "quite a challenge," said Metz.
"I think this will be the scientific imperative" propelling action, said Stephanie Tunmore of the Greenpeace environmental group, an observer at the talks.
The agreement was seen as a personal triumph for the IPCC chairman, Rajendra Pachauri of India, who presided with no-nonsense efficiency and bulldozed through compromise language. Pachauri, who will accept the IPCC's Nobel Peace prize in Oslo on Dec. 10 along with former US Vice President Al Gore, is expected to stand for re-election as head of the IPCC next year, delegates said.
Delegates said the talks this week were difficult, and sometimes bogged down for hours over a brief phrase.
The outcome was "much better than I expected," said Jean-Pascal van Ypersele, the chief scientist of the Belgian delegation. The report was not just "a cut-and-paste" job from earlier papers, but it highlighted more clearly than before the risks faced by the Earth's most vulnerable systems, he said.
The meeting in the Indonesian resort of Bali starting Dec. 3 will discuss the next step in combating climate change after the measures adopted in the Kyoto Protocol expire in five years. Kyoto obliges 36 industrial countries to radically reduce their carbon emissions by 2012, but has no clear plan for what happens after that date.
Organizers say the new "road map" emerging from Bali should draw in the United States, which rejected the Kyoto accord and which has tried to enlist other countries in voluntary schemes to reduce emissions of greenhouse gases and invest in technology research.