Chilling facts of a hotter Arctic - Global warming irreversible...

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The New York Times.

October 25, 2005

 

The Big Melt

No Escape: Thaw Gains Momentum

By ANDREW C. REVKIN

 

In 1969 Roy Koerner, a Canadian government glaciologist, was one of four men (and 36 dogs) who completed the first surface crossing of the Arctic Ocean, from Alaska through the North Pole to Norway.

Now, he said, such a trek would be impossible: there is just not enough ice. In September, the area covered by sea ice reached a record low. "I look on it as a different world," Dr. Koerner said. "I recently reviewed a proposal by one guy to go across by kayak."

At age 73, Dr. Koerner, known as Fritz, still regularly hikes high on the ancient glaciers abutting the warming ocean to extract cores showing past climate trends. And every one, he said, indicates that the Arctic warming under way over the last century is different from that seen in past warm eras.

Many scientists say it has taken a long time for them to accept that global warming, partly the result of carbon dioxide and other heat-trapping gases in the atmosphere, could shrink the Arctic's summer cloak of ice.

But many of those same scientists have concluded that the momentum behind human-caused warming, combined with the region's tendency to amplify change, has put the familiar Arctic past the point of no return.

The particularly sharp warming and melting in the last few decades is thought by many experts to result from a mix of human and natural causes. But a number of recent computer simulations of global climate run by half a dozen research centers around the world show that in the future human influence will dominate.

Even with just modest growth in emissions of the greenhouse gases, almost all of the summer sea ice is likely to disappear by late in the century. Some of the simulations, including those run on an advanced model at the National Center for Atmospheric Research in Boulder, Colo., show much of the summer ice disappearing by 2050, said Marika Holland, a scientist there who is working on the sea-ice portion of that model.

Of the various simulations, all done for an international scientific report on climate trends to be issued in 2007, the only ones that retain much summer sea ice in the Arctic by 2100 are those that assume global greenhouse-gas emissions are held constant at rates measured in 2000 - something that only five years later is already impossible.

The other models all produce an Arctic Ocean in summer akin to the "open polar sea" that was sought by oceanographers and explorers in the mid-1800's. "There would definitely be shipping along the Eurasian coast, and the polar bears would have some serious issues," Dr. Holland said.

The models are, of course, impressionistic views of a far more complicated Arctic reality, so their projections are uncertain. But what worries field scientists, who form their opinions based on empirical clues embedded in ice or recorded by thermometers, is that observations of change and evidence pointing to past patterns are agreeing with the models.

David Barber, an Arctic expert at the University of Manitoba, said emissions needed to be cut quickly to avert even greater damage. Skeptics who use the uncertainties to justify delaying such actions forget that uncertainty cuts both ways, and things could be far worse than forecast, Dr. Barber and others say.

"I wish we would have started 50 years ago, but to not start now would be a real tragedy," Dr. Barber said.

But, he added, it is important to accept that shrinking summer sea ice over the next century is inevitable and that humans need to adapt.

That inevitability presents a sticky problem for environmental groups, many of which have suggested that cutting greenhouse gases could save the polar bear and Eskimo traditions, both dependent on sea ice.

"Even if you would stop every engine right now, there is no escape unless you physically take the CO2 out of the air again," said Henk Brinkhuis, an expert on past Arctic ecosystems at Utrecht University in the Netherlands. He added that this would have to be done on a vast scale, far beyond simply planting trees or the like.

"You may argue for a long time whether this process will take 20, 50 or 100 years, but it doesn't change the fact that it will happen," Dr. Brinkhuis said.

 

http://www.nytimes.com/2005/10/25/science/earth/25arctic.html?oref=login

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