PARIS -- Scientists from across the world gathered Monday to hammer out the final details of an authoritative report on climate change that is expected to project centuries of rising temperatures and sea levels unless there are curbs in emissions of carbon dioxide and other gases that trap heat in the atmosphere.
Scientists involved in writing or reviewing the report say it is nearly certain to conclude that there is at least a 90 percent chance that human-caused emissions are the main factor in warming since 1950. The report is the fourth since 1990 from the Intergovernmental Panel on Climate Change, which is overseen by the United Nations.
The report, several of the authors said, will describe a growing body of evidence that warming is likely to cause a profound transformation of the planet.
Three large sections of the report will be forthcoming during the year. The first will be a summary for policy-makers and information on basic climate science, which is expected to be issued Friday.
Among the findings in recent drafts:
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* The Arctic Ocean could largely be devoid of sea ice during summer later in the century.
* Europe's Mediterranean shores could become barely habitable in summers, while the Alps could shift from snowy winter destinations to summer havens from the heat.
* Growing seasons in temperate regions will expand, while droughts are likely to ravage further the semiarid regions of Africa and southern Asia.
"Concerns about climate change and public awareness on the subject are at an all-time high," the chairman of the panel, Rajendra Pachauri, told delegates on Monday.
But scientists involved in the effort warned that squabbling among teams and government representatives from more than 100 countries over how to portray the probable amount of sea-level rise during the 21st century could distract from the basic finding that a warming world will be one in which retreating coastlines are the new normal for centuries to come.
Jerry Mahlman, an emeritus researcher at the National Center for Atmospheric Research in Boulder, Colo., who was a reviewer of the report's single-spaced, 1,644-page summary of climate science, said most of the leaks to the media so far were from people eager to find elements that were the most frightening or the most reassuring.
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 still is 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 long period of rising sea levels that will almost certainly continue for 1,000 years or so.
