We covered this topic before on WUWT, but it showed up again in this week’s AGU highlights. Given the attention to the recent Arctic sea ice low and quick turnaround, I thought it would be appropriate to mention again.
From the American Geophysical Union highlights
The Arctic has been losing sea ice as Earth’s climate warms, and some studies have suggested that the Arctic could reach a tipping point, beyond which ice would not recover even if global temperatures cool down again. However, a new study by Armour et al. using a state-of-the-art atmosphere-ocean global climate model finds no evidence of such irreversibility. In their simulations, the researchers increase atmospheric carbon dioxide levels until Arctic sea ice disappears year-round and then watch what happens as global temperatures are brought back down. They find that sea ice steadily recovers as global temperatures drop. An implication of this result is that future sea ice loss will occur only as long as global temperatures continue to rise.
Source: Geophysical Research Letters, doi:10.1029/2011GL048739, 2011 http://dx.doi.org/10.1029/2011GL048739
Title: The reversibility of sea ice loss in a state-of-the-art climate model
Authors: K. C. Armour: Department of Physics, University of Washington, Seattle, Washington, USA;
I. Eisenman: Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA, and Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA;
E. Blanchard-Wrigglesworth, K. E. McCusker, and C. M. Bitz: Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA.
Key Points
- Sea ice loss is reversible within a state-of-the-art global climate model
- We find no evidence of threshold behavior in summer or winter sea ice cover
- Rapid sea ice retreat does not imply irreversibility
Abstract:
Rapid Arctic sea ice retreat has fueled speculation about the possibility of threshold (or ‘tipping point’) behavior and irreversible loss of the sea ice cover. We test sea ice reversibility within a state-of-the-art atmosphere–ocean global climate model by increasing atmospheric carbon dioxide until the Arctic Ocean becomes ice-free throughout the year and subsequently decreasing it until the initial ice cover returns. Evidence for irreversibility in the form of hysteresis outside the envelope of natural variability is explored for the loss of summer and winter ice in both hemispheres. We find no evidence of irreversibility or multiple ice-cover states over the full range of simulated sea ice conditions between the modern climate and that with an annually ice-free Arctic Ocean. Summer sea ice area recovers as hemispheric temperature cools along a trajectory that is indistinguishable from the trajectory of summer sea ice loss, while the recovery of winter ice area appears to be slowed due to the long response times of the ocean near the modern winter ice edge. The results are discussed in the context of previous studies that assess the plausibility of sea ice tipping points by other methods. The findings serve as evidence against the existence of threshold behavior in the summer or winter ice cover in either hemisphere.
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So they modeled that water freezes over at low temperature. Who would say that?
Who’d have thought. If it gets too hot it melts. If it gets cold again it comes back.
Can i have some money please?
So the fact that Arctic ice melts during the summer and then refreezes during the winter hadn’t given them a tip that when it gets cold enough water turns to ice?
When it’s cold enough, water freezes?! Wow, who knew. So glad we have sophisticated climate models to let us know.
You mean ice cover follows a cyclic pattern?
The earth in the distant past was green from pole to pole. Sea level was some 100 meters higher than today due to no Antarctic ice cap and temperate forests grew there. These are well known facts. So how could anyone seriously suggest that Arctic sea ice, once melted, can’t ever come back? That’s absurd on the very face of it. It has melted before and it’s back now. The only thing more absurd is that anyone would waste time or money arguing with such an absurdity.
Common sense says that the sum of all climate feedbacks must work towards equilibrium, and no ‘tipping points’ exist in climate, or else the various massive vulcanism, asteroid strikes, continent-wide fires, etc over the millennia would have tipped the climate a long time ago.
That would be a very interesting winter during which there is no ice in the arctic, considering the sun is not even coming up during polar night . Do these guys ever switch on their most basic brain functions?
I’d bet the warmistas response will be that the ice loss is irreversible because the C02 increase will be irreversible because CO2 sticks around for hundreds or maybe even a thousand years even though the 5-7 year period is better supported.
To paraphrase the authors themselves, this is the ‘state of their art’.
Such was my suspicion.
Are there any planned archeological expeditions in the future to these new ice-free areas in Greenland? Surely something interesting is to be found where no man has ever gone before.
Would actual evidence that humans did set foot in these unprecedented ice-free areas during the Medieval Warm Period be “inconvenient”?
“using a state-of-the-art atmosphere-ocean global climate model”
bored..
So this is based on a “state-of-the-art atmosphere-ocean global climate model.” They’re even projecting atmospheric carbon dioxide levels increasing to the point where “Arctic sea ice disappears year-round”—meaning ice won’t form even during Arctic winter. How many times did they have to double CO2 levels to get that result, I wonder. ::facepalm:: It would have more convincing if they’d based it on evidence that the Arctic has been warmer and ice-free in the past, and lo and behold! There’s ice again! But that way, they wouldn’t have been able to tie their “results” to CO2, would they?
There ought to be a funded prize for the most useless ‘research – if modeling can ever be THAT! – in ‘climate science.’ The Ignobel Prize deserves worthy competition.
shocking revelations (!)
This 2004 paper “Variations in the Age of Arctic Sea-ice and Summer Sea-ice Extent” by Ignatius G. Rigor & John M. Wallace, found that;
“The winter AO-index explains as much as 64% of the variance in summer sea-ice extent in the Eurasian sector, but the winter and summer AO-indices combined explain less than 20% of the variance along the Alaskan coast, where the age of sea-ice explains over 50% of the year-to year variability. If this interpretation is correct, low summer sea-ice extents are likely to persist for at least a few years. However, it is conceivable that, given an extended interval of low-index AO conditions, ice thickness and summertime sea-ice extent could gradually return to the levels characteristic of the 1980′s.”
http://seaice.apl.washington.edu/IceAge&Extent/Rigor&Wallace2004.pdf
There is a temptation to be scornful of this study and that was my first thought, as indeed it is of most people who have at least half a brain. But this study is very useful in so far as it is a peer reviewed study from a presumably trusted source with a degree of authority. As such it can be cited every time that an alarmist scientist or commenter makes a claim about a tipping point in the Arctic.
That means yet another journal editor will have to resign for letting such a sloppy piece of work get through.
John Marshall says:
September 21, 2011 at 3:23 am
You mean ice cover follows a cyclic pattern?
NO JOHN They mean that water freezes when it’s cold enough and thaws when it’s warm enough. For that the tax payers paid a full team of people, super computer time, editors and reviewers. Stupid or what?
People get grants for the darnedest things. Your money at work I suspect.
And the alarmists still wonder why we don’t believe them??? Who are the real ‘deniers’ here? Those of us who deny a looming catastrophe for which there is NO current evidence? Or those of them who are in complete denial of the basic laws of physics and reality?
It gets warmer than zero degrees Celsius and ice will melt. It gets colder than zero,* water freezes into ice.
Where is the new revelation?
* Obviously allowing for salination, pressure and any other variables which change the exact freezing point by a tiny amount.
It’s a model based on increasing CO2 until Arctic ice disappears during winter.I wonder what CO2 level caused the ice to disappear? Must be pretty high – higher than realistically possible before the next ice age. In any event do they even haveproof that any event of CO2 increase can increase temperatures to eliminate Arctic winter ice?
Elimination of Arctic sea ice, at least in the summer, would be a huge economic benefit to Eurasia. In fact, a good, stiff dose of global warming would open up millions of square miles of Siberia and Canada to human settlement and lead to massive economic development.
If only the carbon dioxide theory were true, we could make a better world.
“State-of-the-art” — this prescient artist predicted what the models are just now painting: http://en.wikipedia.org/wiki/The_Persistence_of_Memory
I think I see forlorn polar bears in the distance.
The garbage starts as soon as they mention raising the CO2 until the warming melts the Arctic ice. Their model sucks already, being obviously heavily, as usual, into CO2—with the inherent idea (between the lines) that to bring the temperature down, we would have to decrease CO2 (emissions).
They also seem to think that radiative cooling to space, while the Arctic region spends the majority of its year with virtually no solar input (3% of normal direct solar input at the height of the summer), would not yield enormous amounts of ice every long winter and give the Arctic ice a new start every year.
The whole “tipping point” concept has no validity, one has never been shown, and the ranges of conditions they are panicking over are within historical ranges in which nothing, no tipping points, has happened. Tipping points are designed to scare people and are simply the scientific version of the Boogey Man in the closet.
Why does the animation of the Arctic ice extent stop at 2007? Hmmmm?