A provocative new study of the record-setting Arctic thaw that’s unlocking the Northwest Passage and transforming Canada’s polar frontier has, for the first time, drawn a clear connection between rising global carbon pollution and the retreat of sea ice.

The study by top Norwegian climate researcher Ola Johannessen, to be published in October by the Chinese Academy of Sciences but obtained Friday by Canwest News Service, identified a “strengthening linkage” between the upward trend in CO2 emissions over the past century and the shrinking of the Arctic ice cap, which reached a historic minimum last year and appears headed for similar decreases this summer.

Fuente: http://www.nationalpost.com/news/story.html?id=695981At a time when Canada’s next federal election is expected to turn on the debate over a proposed Liberal carbon tax, the scientific paper could add weight to arguments urging sharp reductions in carbon emissions to help slow or reverse climate-change impacts.

More than anywhere else on Earth, those effects have been highlighted by the Arctic meltdown in the Canadian North. And the issue was dramatized again this week in Canada by the collapse of part of the Ward Hunt Ice Shelf above Ellesmere Island and the unprecedented evacuation of tourists from a Baffin Island park experiencing oddly warm temperatures and a high risk of flash flooding.

Johannessen’s study, describing the state of Arctic Ocean ice as a “keystone indicator” of global climate change, concludes that “90% of the decreasing sea-ice extent is empirically ‘accounted for’ by the increasing CO2 in the atmosphere” and that his tracking of the tight relationship between carbon pollution and the size of the ice cap points to “substantially faster ice decreases up to 2050 than predicted by IPCC models” — the forecasts produced by the Nobel Peace Prize-winning international scientific panel on climate change.

“Our projections for sea-ice extent in 2050 are several million square kilometres lower that the IPCC” predictions, the University of Bergen researcher notes in the study, “Decreasing Arctic Sea Ice Mirrors Increasing CO2 on Decadal Time Scale.”

The study also warns that calculations of sea-ice response to CO2 emissions could become meaningless if, as some scientists have conjectured, the planet reaches “a critical ‘tipping point’ for sea ice” when increasingly exposed Arctic waters absorb so much heat it triggers a rapid and irreversible depletion of the remaining year-round ice.

“The extreme record low minimum sea-ice extent observed in September, 2007, may represent crossing such a threshold towards a new state,” the paper states. “On the other hand, it may well be merely a temporary excursion due to a conjunction of anomalous conditions.”

Earlier this year, scientists said last summer’s extreme melt had left the Arctic ice cap weakened and vulnerable to even greater losses during the 2008 melt season, possibly resulting in open water at the North Pole for the first time in recent history.

But more recent observations of the ice cover, along with analyses of melt rates, wind patterns and ocean currents, suggest the 2008 sea-ice minimum — likely to be reached in mid-September — will be slightly larger than last year’s record-setting low.

Still, scientists expect the Northwest Passage through Canada’s Arctic islands to become a reliable summer shipping route within a few decades, and the five nations with Arctic Ocean coastlines — Canada, Russia, Norway, Denmark (Greenland) and the U.S. (Alaska) — are currently scrambling to secure rights to Arctic seabed territory and the potential treasure house of offshore oil and gas in the polar region.

The twin prospects of environmental crisis and economic opportunity in the changing Arctic have also put scientific research about the north under the spotlight in recent months. A U.S. study released last week concluded that smoke from forest fires could shield the Arctic ice from the sun’s melting rays but also warned that soot deposited on polar snow and ice could increase the region’s absorption of heat and wipe out any protective benefits of the smoke.