He added in an interview that such efforts distracted from the basic, undisputed findings, saying that those point to trends that are very disturbing.

He noted recent disclosures that there is still uncertainty about the pace at which seas will rise because of warming and the melting of terrestrial ice over the next 100 years. That span, he said, is just the start of a rise in sea levels that will almost certainly continue for 1,000 years or so.

Many economists and energy experts long ago abandoned any expectation that it would be possible to avoid a doubling of preindustrial carbon dioxide concentrations, given the growth of human populations, use of fossil fuels, particularly coal, and destruction of forests in the tropics.

The report is likely to highlight the hazardous consequences of that shift by finding that reaching twice the preindustrial concentration of carbon dioxide will probably warm climate between 3.5 and 8 degrees Fahrenheit and by highlighting that there is a small but significant risk that such a buildup can produce even more warming.

One major point of debate in early drafts of the report is the projection of a smaller rise in sea level than the last report as scientists relying on computer models and field observations struggle to find a consensus. Some scientists say that the figures used in the coming report are not recent enough because they leave out recent observations of instability in some ice sheets in Antarctica and Greenland.

Another possible point of contention during the four days of closed sessions in Paris this week may be assertions in early drafts of the report that the recent warming rate was blunted by particle pollution and volcanic eruptions.

Some scientists say the final report should reflect the assumption that the rate of warming in coming years is likely to be more pronounced than that of previous decades.