Hundreds of scientists and bureaucrats have been editing the new report, which must be unanimously approved by the panel, during closed-door meetings in Paris.
“Global warming and bird-flu are a greater threat to most of us than terrorism” Shafiq, Dhaka, Bangladesh
The panel, which includes 2,500 scientists from 130 countries, is also expected to say that ocean levels will continue to rise for more than 1,000 years even if governments stabilise greenhouse gas emissions.
The report will be the first of four this year by the panel that will outline the danger of global warming.
Delegates said the Paris meeting later agreed a “best estimate” that temperatures will rise by between 1.8 and 4.0C by 2100 over pre-industrial levels, the biggest change in a century for thousands of years.
The draft accord projects that Arctic ice will shrink, and perhaps disappear in summers by 2100, while heat waves and downpours would get more frequent.
The Gulf Stream that brings warm waters to the North Atlantic could slow, although a shutdown is highly unlikely, it concludes.
Sea levels are likely to rise by between 28 and 43cm this century, a lower range than forecast in 2001. Rising seas threaten low-lying Pacific islands and low-lying coastal nations from Bangladesh to the Netherlands.
In advance of the report’s release, the lights on the Eiffel Tower in Paris were turned off as part of a campaign to highlight the threat of global warming.