Arctic icecap safe from runaway melting: study

Dec 15, 2010 by Marlowe Hood
Ice Fjord of Ilulissat in Greenland. 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.

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 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 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 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 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 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.

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User comments : 8

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jscroft
2.7 / 5 (7) Dec 15, 2010
Well, THAT's inconvenient.
MikPetter
4 / 5 (2) Dec 15, 2010
From the article "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"
rwinners
4.3 / 5 (4) Dec 15, 2010
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.

GOOD LUCK! I'll bet dollars to donuts that the increase isn't even halted.
Howhot
1.6 / 5 (7) Dec 15, 2010
"indicates that IF ANNUAL EMISSIONS of GREENHOUSE gases ARE SUBSTANTIALLY REDUCED over the next two decades"; Where are you gswift7 and the other AGW Deniers that are being paid by (insert your fav here) to post BS on a science website. To the AGWD's; read my middle finger; I hope your kids have fun in 120+ F city hell.
GSwift7
3.8 / 5 (5) Dec 16, 2010
This isn't new. Models vary, but some have always indicated that there's no tipping point, while others still say that there is a tipping point.

I don't really like polar bears though. They are too tough, even when you slow cook them. Oh relax, I was kidding. I've only eaten black bears. Imagine having the very last polar bear rug, that would be great!

Seriously though. A little critical thinking, if you don't mind. Can you think of any reason besides caring about God's creatures (lol) that someone might want to get polar bears listed as "endangered" rather than "threatened"? If they want polar bears reclasified, shouldn't they be talking about polar bear population numbers? Why aren't there any numbers like that here? Can you think of any reason that they might want to establish a strong link between polar bears, extinctions, and global warming? Think EPA, lawyers, and money and you'll be on the right track.
GSwift7
4 / 5 (4) Dec 17, 2010
Oh by the way, official records indicate that (to the best of our knowledge) polar bear populations are in decline. Adult size and weight as well as birth numbers and weights are doing down. Those numbers would clearly support the above article, so it's fishy that they don't mention it.

The above comments that suggest polar bear numbers are increasing are baseless as far as I can find. Those statements are only based on "reports of increased sightings by locals" not on actual tagging, tracking, and weight measurements.

On the other hand, it's probably a little misleading to say that polar bears will go extinct. It's more likely that they will increasingly interbreed with brown bears and kodiak bears until the species re-mix and become a single species again. That happens all the time with nich species. They come and go all the time. I'm not saying that's good, but it's not the end of the world.

unless you're a polar bear.
Skeptic_Heretic
5 / 5 (3) Dec 17, 2010
Well, THAT's inconvenient.

No, it's actually quite convenient. It simply means that the melt could be seasonal, driven by man, driven by factors other than man, and isn't a permanent or catastrophic situation.

If this study stands, we can all be relieved that there isn't a point of no return in regards to sea ice.
Where are you gswift7 and the other AGW Deniers that are being paid by (insert your fav here) to post BS on a science website.
GS is rationally skeptical, some others on this site on both sides of the discussion should adopt a more similar stance.

I think AGCC is happening, I'm skeptical of some of the statements aligned with the theory. GS thinks AGCC is happening, he's skeptical of some of the statements aligned with the theory.

We hold rather different viewpoints on what we should do about it based on where our skepticism lies.

Spend your time reading rather than decrying others.
Christopher_Hanks
not rated yet Dec 23, 2010
I'm a little stunned at how Amstrup's work is being interpreted, both here an in the mainstream press. His paper says only that a tipping point can be avoided, this by freezing GHG emissions by 2020. His paper also clearly indicates that the A1B "business as usual" model *does* result in a tipping point and 100% ice loss.

And even then, his model shows that the ice caps only recover to 50%. I'm not sure anyone can call that "recovery." Not the Dutch, anyway.

We can -- possibly -- avoid a tipping point, but the point of the paper is that action must be taken now.