World governments should take heed of the most wide-ranging scientific assessment so far of a human link to global warming and agree prompt action to slow the trend, the chairman of a U.N. climate report said on Monday.
A draft of the report, due for release on Friday, projects a big rise in temperatures this century and warns of more heatwaves, floods, droughts and rising sea levels linked to greenhouse gases, released mainly by the use of fossil fuels.
"I hope policies and action will be formed to address the problem," Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change (IPCC), told reporters.
"I think, based on the awareness that is growing very rapidly in every part of the globe, you will see a certain political resolve developing."
Governments and scientists began a final review of the IPCC draft in Paris on Monday before its release on February 2.
The report draws on research by 2,500 scientists from more than 130 countries and has taken six years to compile. It is unlikely there will be major changes between the draft and the final conclusions, according to diplomatic sources.
Thirty-five industrial nations have signed up to the United Nations' Kyoto Protocol, capping emissions of carbon dioxide.
The United States pulled out in 2001, arguing that Kyoto would cost jobs and wrongly excluded developing nations from goals for 2012. Still, President Bush said last week that climate change was a "serious challenge."
The draft report says there is at least a 90 percent probability that human activities are to blame for most of the warming in the past 50 years. The previous report, in 2001, put the probability at 66 percent.
The U.N. report, the fourth of its kind, is expected to foresee global average temperatures rising to 2.0 to 4.5 degrees Celsius (3.6 to 8.1 Fahrenheit) above pre-industrial levels by 2100, with a "best estimate" of a 3.0 C (5.4 F) rise.
Around 40 Greenpeace activists climbed Paris's Eiffel Tower on Monday to put up two banners pressing for urgent action on climate change. One read: "It's not too late."