Scientists: It's not too late yet for polar bears

Yahoo News 15 Dec 10;

ANCHORAGE, Alaska – Two groups of scientists are suggesting a sliver of hope for the future of polar bears in a warming world.

A study published online Wednesday rejects the often used concept of a "tipping point," or point of no return, when it comes to sea ice and the big bear that has become the symbol of climate change woes. The study optimistically suggests that if the world dramatically changed its steadily increasing emissions of greenhouse gases, a total loss of critical summer sea ice for the bears could be averted.

Another research group projects that even if global warming doesn't slow — a more likely near-future scenario — a thin, icy refuge for the bears would still remain between Greenland and Canada.

A grim future for polar bears is one of the most tangible and poignant outcomes of global warming. Four years ago, federal researchers reported that two-thirds of the world's polar bear habitat could vanish by mid-century. Other experts foresee an irreversible ice-free Arctic in the next few years as more likely.

The new study, which challenges the idea of a tipping point, says rapid ice loss could still happen, but there's a chance that the threatened bears aren't quite doomed.

"There is something that can be done to save polar bears," said lead author Steven Amstrup, the former senior polar bear scientist for the U.S. Geological Survey in Alaska. "The problem is not irreversible."

His research, published in Nature, shows there's a steady relationship between greenhouse gas emissions, sea ice and polar bear habitat. As emissions rise, sea ice and polar bear habitat decline. But unlike previous research, there's no drop-off tipping point in Amstrup's models.

Essentially until all sea ice is gone permanently in the summer there is still a chance to prevent the worst-case, if global warming is stopped in time, Amstrup's research shows.

"Such a tipping point would mean that future reductions in greenhouse gas emissions would do little to save the polar bear," said Amstrup, who is now chief scientist for the conservation group Polar Bears International. "It seems clear that if people and leaders think that there's nothing they can do, they will do nothing."

Some experts called Amstrup too optimistic, but said his computer models made sense.

"I wouldn't say that we can rule out a tipping point, but it does show that a tipping point isn't inevitable," said Walt Meier, a senior scientist at the National Snow and Ice Data Center in Boulder, Colo.

But that all hinges on reducing greenhouse gas emissions — carbon dioxide and other pollution from the burning of fossil fuels, said Mark Serreze, director of the center. "Time is running out. Humankind needs to make a choice," he said.

Time has already run out, said Henry Jacoby, a management professor at MIT and founder of its MIT Global Change Joint Program.

Jacoby examined the computer models Amstrup used in his paper and said it is based on a "world that's already long gone." The two scenarios of emission reductions are points that the world has already passed or will pass in the next few years, Jacoby said.

After the global recession led to a one-year dip in carbon dioxide emissions, they are soaring again, according to a recent study. And vague international agreements made in Cancun last week and in Copenhagen last year don't do enough, Jacoby said.

"Even given the pledges on the table, we don't come close to what these guys use in their hopeful scenario," he said.

Study co-author Eric DeWeaver of the National Science Foundation called the scenarios he used "plausible."

But DeWeaver and Amstrup agree the polar bear is in deep trouble if emissions continue to rise as they are now.

A second study was to be presented Thursday at the American Geophysical Union conference in San Francisco. That research considers a future in which global warming continues at the same pace.

And it shows that a belt from the northern archipelago of Canada to the northern tip of Greenland will likely still have ice because of various winds and currents.

The sea ice forms off Siberia in an area that's called "the ice factory" and is blown to this belt, which is like an "ice cube tray," said Robert Newton of the Lamont-Doherty Earth Observatory at Columbia University.

That "sea ice refuge" will be good for polar bears and should continue for decades to come, maybe even into the next century, he said.

Just how many polar bears could live there still has to be figured out, according to the research by Newton and Stephanie Pfirman of Barnard College.

Amstrup's study doesn't downplay the nature of global warming and its effect on polar bears, especially if emissions increase.

"The changes that are occurring in the Arctic are going on at a much more rapid rate than elsewhere in the world," Amstrup said. "So the changes that are occurring and affecting polar bears really foreshadow much more significant changes that are likely to occur worldwide."

Polar Bears Not Doomed if Swift and Serious Action is Taken
livescience.com Yahoo News 15 Dec 10;

Polar bears, considered doomed if the Arctic sea ice continues to melt, have a fighting chance at survival if humans cut back on their emission of greenhouse gases, according to a new study.

"Our research offers a very promising, hopeful message, but it's also an incentive for mitigating greenhouse emissions," Cecilia Bitz, an atmospheric scientist at the University of Washington in Seattle, said in a statement.

Polar bears were marked as a threatened species in 2008, the year after a study projected that two-thirds of the world's polar bears would be dead within decades if the warming climate kept melting their icy habitat. That study was based on current emissions, according to Steven Armstrup, emeritus researcher with the U.S. Geological Survey, who is also a Polar Bear International senior scientist.

"That was a pretty dire outlook, but it didn't consider the possibility of greenhouse gas mitigation," Armstrup, who led the new study, said in a statement.

Earlier models found that large areas of Arctic ice could disappear in less than a decade. If greenhouse emissions continued as they are now, those studies found, the ice would not recover and could disappear entirely.

Arctic sea ice is crucial to polar bears, providing them access to their favorite food, seals. Without food, polar bears would lose two pounds per day on their way toward starving.

However, the new study, reported Dec. 16 in the journal Nature, finds that if greenhouse gases drop significantly in the near future, bears may not lose their icy hunting grounds. The remaining ice would stay intact through the remainder of the century, and some of the lost ice would re-form, according to the researchers' new model. That would be enough to ensure the survival of the polar bear species, they wrote.

The 2007 study identified two Arctic regions where polar bears were at particular risk.

"There's still a fairly high probability in both of those regions that polar bears could disappear," Armstrup said. "But with mitigation and aggressive management of hunting and other direct bear/human interactions, the probability of extinction would now be lower than the probability that polar bear numbers will simply be reduced."

Arctic icecap safe from runaway melting: study
Marlowe Hood Yahoo News 15 Dec 10;

PARIS (AFP) – There is no "tipping point" beyond which climate change will inevitably push the Arctic ice cap into terminal melt off, according to a study released Wednesday.

The northern polar cap has shrunk between 15 and 20 percent over the last 30 years, unleashing concern that on current trends -- with regional temperature increases twice or triple the global average -- it could disappear entirely during the summer months by century's end.

One of the factors in this calculation is a so-called positive feedback, in which a reduced area of floating ice helps to stoke global warming.

As ice cover recedes decade by decade, more of the Sun's radiative force is absorbed by dark-blue sea rather than bounced back into space by reflective ice and snow.

But a new study published in the British science journal Nature shows that there is nothing inevitable about this process, and that it can be halted or even reversed.

"There is no 'tipping point' that would result in unstoppable loss of summer sea ice when greenhouse gas-driven warming rose above a certain threshold," said Steven Amstrup, a professor at the University of Washington and lead author of the study.

Up to now, many scientists worried that there was an as yet unidentified temperature threshold which, once passed, would doom the ice cap.

But the study, based on computer models, indicates that if annual emissions of greenhouse gases are substantially reduced over the next two decades, an initial phase of rapid ice loss would be followed by a period of stability and, eventually, partial recovery.

If so, that could mean a reprieve for polar bears, which use floating ice shelves as a staging areas for stalking ringed and bearded seals, their preferred food.

Already today, many of the majestic predators are teetering on the edge of starvation because the ice melts sooner in spring and forms later in autumn, shortening their hunting season.

The new research "offers a very promising, hopeful message," said co-author and University of Washington professor Cecilia Blitz.

"But it's also an incentive for mitigating greenhouse gas emissions," she said in a statement.

In earlier research, Amstrup and colleagues had calculated that only a third of the world's estimated 22,000 polar bears would still be around by 2050, and that even these survivors could eventually disappear.

In 2008, Washington listed polar bears under the Endangered Species Act.

Earlier this week, more than 150 biologists and climate scientists called in an open letter on US President Barack Obama to step up action to save the Arctic's top predator.

The US Department of the Interior faces a court-imposed deadline next week on whether polar bears should continue to be classified merely as "threatened" or given maximum protection under US law as "endangered."

And a separate study also published in Nature Wednesday warned that melting ice was pushing Arctic mammals to breed with cousin species, in a trend that could be pushing the polar bear and other iconic animals towards extinction.