IPCC officials declined to comment on the report, saying it would be issued on Friday.
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.
A source told the AFP news agency that, compared with previous IPCC gatherings, "there is a strikingly low degree of conflict and a high degree of agreement by governments" on the core conclusions that the planet is warming and mankind is overwhelmingly responsible for it.
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.Shrinking ice
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 numbers of tropical hurricanes might decrease but the storms would become stronger.
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.
France's Alliance for the Planet conservation group organised the five-minute long nationwide lights-out, which was also observed by the Hilton hotel where many of the conferences delegates are staying. Several other European cities also staged symbolic blackouts.