Climate experts warned this morning that global warming will cause faster and wider damage than previously forecast, ranging from hunger in Africa and Asia to extinctions and rising ocean levels.
More than 100 nations in the UN climate panel agreed a final text after all-night disputes with some scientists accusing government delegates of watering down their findings in a draft 21-page summary for policymakers.
"We have an approved report," Rajendra Pachauri, the chair of the Intergovernmental Panel on Climate Change (IPCC), told reporters after the talks in Brussels.
The report by the IPCC, the top world authority on climate change grouping 2,500 scientists, will guide policy in coming years on issues such as extending the UN's Kyoto Protocol beyond 2012.
"Conflict is a hard word, tension is a better word," Gary Yohe, one of the report's lead authors, said when asked to describe the mood at the marathon talks.
He said China, Russia and Saudi Arabia had raised most objections during the night to a 21-page summary which makes clear that the poor will suffer most. Other participants also said the United States had toned down some passages.
Some scientists objected, for instance, after China tried to eliminate a note saying that there was "very high confidence" that climate change was already affecting "many natural systems, on all continents and in some oceans".
China, the second largest source of greenhouse gases after the United States and ahead of Russia, wanted no mention of the level of confidence.
Still, delegates sharpened other sections, including adding a warning that some African nations might have to spend 5 to 10 per cent of gross domestic product on adapting to climate change.
Overall, the report is the bleakest U.N. assessment yet of the threat of climate change, predicting water shortages that could affect billions of people, extinctions of species and a rise in ocean levels that could go on for centuries.
It says human greenhouse gas emissions, mostly from burning fossil fuels, are very likely to be the main cause of warming. It also says climate change could cause a sharp fall in crop yields in Africa, a thaw of Himalayan glaciers and more heatwaves for Europe and North America.
In one section, the IPCC toned down risks of extinctions.
"Approximately 20-30 per cent of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5 degrees Celsius (2.7-4.5 Fahrenheit)," the text said.
A previous draft had said 20-30 percent of all species would be at "high risk" of extinction with those temperature rises.
U.S. delegates rejected suggested wording that parts of North America may suffer "severe economic damage" from warming.
But it toughened some sections by saying "significant loss of biodiversity" was possible in parts of Australia such as the Great Barrier Reef by 2020.
The IPCC report says climate change is no longer a vague, distant threat.
"The whole of climate change is something actually here and now rather than something for the future," said Neil Adger, a British lead author of the report.