Far North Science

The noxious combustion that powers modern human society — from thousands of power plants to vast industrial agriculture to a billion commuting automobiles — has triggered climate warming and sea level rise that will continue for 1,000 years, scientists with the Intergovernmental Panel on Climate Change warned Friday morning during a news conference in Paris.

“Warming of the climate system is now unequivocal,” said Susan Solomon, co-chair of the group that wrote the report, in a broadcast piped live over the Internet about midnight Alaska time. “It’s very likely that most of the observed increase in globally averaged temperatures since the 20th century is due to the observed increased in greenhouse gas concentrations.”

If emissions of carbon dioxide and methane from human activities continue to rise at rates clocked during recent decades, the consequences will grow worse or arrive sooner, the scientists said. The time to respond has arrived.

The issue is no longer whether human activity is driving climate warming, but “what on Earth are we going to do about it,” said UNEP Executive Director Achim Steiner. “It shifts from doubting to having to act.

“Even if the last element of certainty is not yet there, I think anyone who would continue to risk inaction, on the basis of the evidence presented here, will one day in the history books be considered irresponsible.”

Carbon dioxide levels and other greenhouse gases are now at concentrations unseen on Earth in about 650,000 years, forcing the atmosphere to retain ever more solar energy as heat. Detailed studies from air trapped in ice cores and peat show gas levels began to spike during the Industrial Revolution in the 1700s and continue to rocket up.

The results are now transforming the world.

Over the rest of this century, the average global temperatures could rise 3 to 11 degrees Farhenheit. Arctic late-summer ice cover will almost certainly disappear, drastically reducing the habitat of species like polar bears and seals.

Heatwaves will scorch. Stronger hurricanes will devastate. Snow and rain will increase in the Far North while droughts bake the tropics. Weather will grow more extreme. And sea level could rise anywhere from seven inches to nearly two feet, though many scientists say the fast-increasing meltdown of the Greenland ice sheet and disintegration of Antarctic shelves could inundate these predictions.

Keep it up this heat for centuries, and the entire Greenland ice sheet could melt, a situation that last occurred about 125,000 years ago. That scenario raises average ocean levels 22 feet.

Most of these changes will be exaggerated in high latitudes — across Alaska, northern Canda, Siberia and other areas of the Arctic, the scientists said.

“The evidence is on the table and we no longer have to debate that part of it.” said IPCC chair Rajendra Pachauri. “We cannot solve this problem in isolation from one another.”

The predictions came from Climate Change 2007 a 21-page “summary for policymakers” drawn from the IPCC’s fourth comprehenisve analysis of climate change, the first since 2001.

More than 600 primary authors from 40 countries shared results and worked over data during the past six years. Scientists from 13 nations ran 23 of the most sophisticated climate models ever developed through supercomputers to conjure statistical visions of the future world. The results were reviewed by 600 experts, and 300 delegates from 130 countries met in Paris this week to tune up the final document.

Three more reports with detailed evidence are due out later this year. Check the IPCC web site in May.

An audio file of the press conference and presentation was posted online.