The United Nations' expert panel on climate science says there's "conclusive evidence" that humans are altering the Earth's climate system.
A report, which combines the findings of three earlier reports, was adopted after all-night talks that went on until 5am on Saturday by the Intergovernmental Panel on Climate Change.
The scientists and government representatives on the panel, who jointly approved the document line by line, then rested for a few hours before resuming the session in Copenhagen to finish the document.
The report is scheduled to be released to the public on Sunday.
Apart from discussing the human influence, the report is expected to describe how climate impacts, including melting Arctic sea ice and rising levels, are already happening and could become irreversible unless the world curbs its greenhouse gas emissions.
The scientists and government representatives on the panel, who jointly approved the document line by line, then rested for a few hours before resuming the session in Copenhagen to finish the document.
The Intergovernmental Panel on Climate Change says scientists are now 95 per cent certain that the buildup of such gases from the burning of fossil fuels and deforestation is the main cause of warming seen since the middle of the 20th century.
IPCC vice chair Jean-Pascal van Ypersele wrote on Twitter that the report was adopted on Saturday afternoon following round-the-clock talks.
The UN Environment Program said the report "offers conclusive scientific evidence that human activities continue to cause unprecedented changes in the Earth's climate".
In an interview with The Associated Press, UNEP head Achim Steiner said the world has the technology and capacity to act, and needs to do so urgently.
The cost of achieving emissions cuts increases exponentially with each year "because you will have to make far more drastic changes in our economy", Steiner said.
While the IPCC tries to avoid explicitly telling governments what they should do, the report will present scenarios showing that warming can be kept in check if the world shifts its energy system toward renewable sources like wind and solar power and implements technologies to capture greenhouse gases from the atmosphere.
