Profound climate changes in store, experts sayPARIS: 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 curbs in emissions of carbon dioxide and other gases that trap heat in the atmosphere are put in place.
According to scientists involved in writing and reviewing the report, the fourth since 1990 from the Intergovernmental Panel on Climate Change, a body overseen by the United Nations, the paper is nearly certain to conclude that there is at least a 90 percent chance that human-caused emissions are the main cause of warming since 1950.
The report, according to several authors, who spoke on condition of anonymity because details could still change, will describe growing evidence that warming is likely to profoundly transform the planet.
Three large sections of the report will be forthcoming during the year, with the summary for policy makers and sections on basic climate science coming Friday.
Among findings in recent drafts are that the Arctic Ocean could largely be devoid of sea ice in summers in this century; the Mediterranean shores of Europe could become barely habitable in summers while the Alps shift from snowy winter destinations to summer havens from the heat; growing seasons in temperate regions will expand, while droughts will further ravage semi-arid 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 climate change panel, Rajendra Pachauri, told delegates Monday.
"It would perhaps be no exaggeration to suggest that, at no time in the past, has there been a greater global appetite for knowledge on any subject as there is today on the scientific facts underlying the reality of global climate change," Pachauri said.
But scientists involved in the effort warned that squabbling between teams and representatives from governments of more than 100 countries over how to portray the most probable rise in sea levels during the 21st century could distract from the basic finding that a warming world will be one in which retreating coasts are the new norm for centuries to come.
Jerry Mahlman, an emeritus researcher at the National Center for Atmospheric Research in Boulder, Colorado, who reviewed the report's single- spaced, 1,644-page summary of climate science, said that most of the leaks to the press so far had been from people eager to find elements that were the scariest or most reassuring.
He added in an interview that such efforts distract from the basic, undisputed findings, saying that those point to trends that are very disturbing.
He pointed to recent disclosures that there was still uncertainty about the pace at which seas will rise due to warming and melting of ice over the next 100 years. That span, he said, was just the start of a process of a rise in sea levels that would then almost certainly continue for 1,000 years or so.
The latest draft of the panel's summary highlights the hazardous consequences of "business as usual," finding that reaching twice the pre-industrial concentration of carbon dioxide in the atmosphere will probably warm the climate 3.5 degrees Fahrenheit to 8 degrees Fahrenheit, or 6.3 degrees Celsius to 14.4 degrees Celsius, with a greater than one- in-ten chance of higher temperatures.
Even the midrange projection for warming, say many climate experts and biologists, will powerfully stress ecosystems and disrupt longstanding climate patterns related to water supplies and agriculture.
Many economists and energy experts long abandoned any expectation that the world can avoid a doubling of pre- industrial carbon dioxide concentrations given the growth of human populations; use of fossil fuels, particularly coal; and deforestation in the tropics.
As a result, a significant focus of the summary coming this week and of other sections of the report will be the necessity to bolster the resilience of agriculture and water supplies to inevitable shifts, while trying to slow and, as soon as it can be affordably done, reverse the century-long climb in releases of the heat-trapping gases.
Many experts involved in drawing up the report said there was hope that with a prompt start on slowing emissions, the chances of seeing much great warmer and widespread disruption of ecosystems and societies can be cut.
Outside experts agreed.
"We basically have three choices — mitigation, adaptation and suffering," said John Holdren, the president of the American Association for the Advancement of Science and an energy and climate expert at Harvard University. "We're going to do some of each. The question is what the mix is going to be. The more mitigation we do, the less adaptation will be required and the less suffering there will be."
One key point of controversy in recent drafts of the summary is a smaller rise in sea level than the last report projected. In the next several days, scientists relying on field observations and computer models of ocean and ice behavior in a warming world will struggle to find a consensus.
Some scientists say that the figures used in the new report are overly conservative because they leave out recent observations of instability in some ice sheets in Antarctica and Greenland.
Ice loss in those regions has been very sudden in some cases, implying a more rapid rise in sea levels than projected by some computer models.
Another possible point of contention during the four days of closed-door sessions in Paris this week could be assertions in early drafts 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 that in previous decades.
The report will not outline measures to tackle global warming. Instead, it will concentrate on the latest evidence that the phenomenon is under way.
But Achim Steiner, executive director of the United Nations Environment Program, said the findings to be presented Friday should lead decision makers to accelerate efforts to slash carbon emissions and to help people in vulnerable parts of the world prepare for climate change.
"These findings should strengthen the resolve of governments to act now to reduce greenhouse gas emissions and put in place the medium to longer term strategies necessary to avert dangerous climate change," Steiner said.
In a new report issued on Monday, UNEP said the most recent evidence from mountain glaciers showed they were melting faster than before, or 1.6 times more than the average of the 1990s and three times the loss rate of the 1980s. UNEP warned that the trend was likely to continue because 2006 was one of the warmest years on record in many parts of the world.
Also Monday, there were new concerns about climate change from low- lying parts of the world. Indonesia could lose about 2,000 islands by 2030 because of warming, Environment Minister Rachmat Witoelar said.
Over the past year, international concern over what to do about global warming has grown along with concrete signs of climate change in developing regions like Africa, where water is running low, and in developed regions, like Europe, where there was a marked lack of snow at Alpine ski resorts in early January.
Even so, political leaders are groping for ways to tackle the problem. Europe has adopted a program that caps the amount of emissions from industrial producers.
But the world's largest emitter, the United States, is still debating whether to adopt a similar policy and developing countries like China are resisting caps on the grounds that the industrialized world contributed about 75 percent of the current volume of greenhouse gases and should make the deepest cuts.
That situation has hampered the chances of an effective solution, which experts say will require all countries to cut emissions or become more energy efficient.
The second section of the new report, which focuses on the impacts of and ways of adapting to climate change, is scheduled for publication in April, while a section on mitigating climate change is to be made public in May.
A synthesis of all three parts for policy makers is expected in November.