Science Panel Calls Global Warming ‘Unequivocal’
Dan Crosbie/Canadian Ice Service
Polar bears on chunks of glacial ice in the Bering Sea in 2004. Much higher temperatures are forecast for the Arctic, climate scientists say.
By ELISABETH ROSENTHAL and ANDREW C. REVKIN Published: February 3, 2007
PARIS, Feb. 2 — In a grim and powerful assessment of the future of the planet, the leading international network of climate scientists has concluded for the first time that global warming is “unequivocal” and that human activity is the main driver, “very likely” causing most of the rise in temperatures since 1950.
Timeline In its fourth assessment of global warming, released Friday, the Intergovernmental Panel on Climate Change used its strongest language yet in drawing a link between human activity and recent warming. Enlarge This Image Reuters.
A worker at an industrial-residue disposal site in Hanshou County in central China Friday. A climate panel has concluded that human industrial activity is “very likely” driving global temperature rises.
They said the world was in for centuries of climbing temperatures, rising seas and shifting weather patterns — unavoidable results of the buildup of heat-trapping gases in the atmosphere.
But their report, released here on Friday by the Intergovernmental Panel on Climate Change, said warming and its harmful consequences could be substantially blunted by prompt action.
While the report provided scant new evidence of a climate apocalypse now, and while it expressly avoided recommending courses of action, officials from the United Nations agencies that created the panel in 1988 said it spoke of the urgent need to limit looming and momentous risks.
“In our daily lives we all respond urgently to dangers that are much less likely than climate change to affect the future of our children,” said Achim Steiner, executive director of the United Nations Environment Program, which administers the panel along with the World Meteorological Organization.
“Feb. 2 will be remembered as the date when uncertainty was removed as to whether humans had anything to do with climate change on this planet,” he went on. “The evidence is on the table.”
The report is the panel’s fourth assessment since 1990 on the causes and consequences of climate change, but it is the first in which the group asserts with near certainty — more than 90 percent confidence — that carbon dioxide and other greenhouse gases from human activities have been the main causes of warming in the past half century.
In its last report, in 2001, the panel, consisting of hundreds of scientists and reviewers, said the confidence level for its projections was “likely,” or 66 to 90 percent. That level has now been raised to “very likely,” better than 90 percent. Both reports are online at www.ipcc.ch.
The Bush administration, which until recently avoided directly accepting that humans were warming the planet in potentially harmful ways, embraced the findings, which had been approved by representatives from the United States and 112 other countries on Thursday night.
Administration officials asserted Friday that the United States had played a leading role in studying and combating climate change, in part by an investment of an average of almost $5 billion a year for the past six years in research and tax incentives for new technologies.
At the same time, Secretary of Energy Samuel Bodman rejected the idea of unilateral limits on emissions. “We are a small contributor to the overall, when you look at the rest of the world, so it’s really got to be a global solution,” he said.
The United States, with about 5 percent of the world’s population, contributes about a quarter of greenhouse gas emissions, more than any other country.
Democratic lawmakers quickly fired off a round of news releases using the report to bolster a fresh flock of proposed bills aimed at cutting emissions of greenhouse gases. Senator James M. Inhofe, the Oklahoma Republican who has called the idea of dangerous human-driven warming a hoax, issued a news release headed “Corruption of Science” that rejected the report as “a political document.”
The new report says the global climate is likely to warm 3.5 to 8 degrees Fahrenheit if carbon dioxide concentrations in the atmosphere reach twice the levels of 1750, before the Industrial Revolution.
Many energy and environment experts see such a doubling, or worse, as a foregone conclusion after 2050 unless there is a prompt and sustained shift away from the 20th-century pattern of unfettered burning of coal and oil, the main sources of carbon dioxide, and an aggressive expansion of nonpolluting sources of energy.
And the report says there is a more than a 1-in-10 chance of much greater warming, a risk that many experts say is far too high to ignore.
Even a level of warming that falls in the middle of the group’s range of projections would be likely to cause significant stress to ecosystems, according to many climate experts and biologists. And it would alter longstanding climate patterns that shape water supplies and agricultural production.
Moreover, the warming has set in motion a rise in global sea levels, the report says. It forecasts a rise of 7 to 23 inches by 2100 and concludes that seas will continue to rise for at least 1,000 years to come. By comparison, seas rose about 6 to 9 inches in the 20th century.
John P. Holdren, an energy and climate expert at Harvard, said the report “powerfully underscores the need for a massive effort to slow the pace of global climatic disruption before intolerable consequences become inevitable.”
Elisabeth Rosenthal reported from Paris, and Andrew C. Revkin from New York. Felicity Barringer contributed reporting from Washington.
