Study suggests Arctic sea ice loss is not irreversible

Arctic Sea ice concentration, biweekly norther...

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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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69 thoughts on “Study suggests Arctic sea ice loss is not irreversible

  1. 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?

  2. 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?

  3. When it’s cold enough, water freezes?! Wow, who knew. So glad we have sophisticated climate models to let us know.

  4. 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.

  5. 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.

  6. 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?

  7. 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.

  8. 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”?

  9. 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?

  10. 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.

  11. 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

  12. 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.

  13. 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?

  14. 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.

  15. 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?

  16. 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.

  17. 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.

  18. I’d really like somebody to show me that these tipping points exists anywhere except in a computer model or a grant proposal for more funding.

  19. Irreversible!! Irrepressible more like.
    I invite everyone to look at those amazing NOAA Arctic timelapse sequences of freeze and thaw…watch especially the rushing currents transporting ice into the oceans and the ease with which it is replenished. …it should be quite obvious to anyone that the Arctic can and will keep pumping out ice until the earth shifts on its axis and there is no longer 3 months of sub-zero darkness.

  20. “higley7 says:
    September 21, 2011 at 6:08 am ”

    Just what I was thinking. This paper supports the skeptical position but it is still beyond crap so endorsing it would be hipocritical. Sorry pseudoscience, you lose. Even the Team will hate you this time, it’s the wrong flavor of pseudoscience.

  21. •Antonio Zichichi, nuclear physicist and President of the World Federation of Scientists: “In the past half billion years, Earth has lost, four times, its polar caps – no ice at either Pole. And, four times, the polar caps were reconstituted. Global warming is caused by unusually high levels of solar radiation and a lengthy – almost throughout the last century – growth in its intensity

  22. liontooth says:
    September 21, 2011 at 4:24 am

    “Are there any planned archaeological 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”?”

    Yeah, it would.

    From the following post/article “…archaeologists had to dig through the permafrost to get at the old Viking farm houses shows…”

    The Fate of Greenland’s Vikings and the falsification of human induced global warming

    http://fgservices1947.wordpress.com/2011/07/23/the-fate-of-greenlands-vikings-and-the-falsification-of-human-induced-global-warming/

  23. A number of people here are identifying the paper as helpful to the sceptic cause. I don’t agree as in the paper a recovery of ice extent rests *entirely* on reducing CO2 to reduce temperature. They aren’t suggesting summer ice won’t disappear, they are saying it will unless we limit atmospheric CO2 levels to limit temperature.

  24. Ice Loss is a pathetic, non-scientific phrase. That water is going nowhere fast. It is not ‘lost’.

    Once again, unless the Earth gets whacked bad by an enormous object and knocked onto its side like Uranus, the axial tilt means it will remain as is, alternating between cold and very cold up there, forever. The current configuration leads to sun up / sun down for long periods each, causing above freezing and below freezing temperatures, which in turn leads to clockwork phase changes between water and ice. This will never be defeated by CO2 levels of any magnitude.. Never! The alarmists have worked themselves up over ice extent occurring during a timespan of perhaps one week out of 52 in a year.

    You want to melt all the ice? Remove the land preventing warmer water into the Arctic. Or, change the axial tilt. CO2? Not a chance. _Wiki_

    “Uranus has an axial tilt of 97.77 degrees, so its axis of rotation is approximately parallel with the plane of the Solar System. This gives it seasonal changes completely unlike those of the other major planets. Other planets can be visualized to rotate like tilted spinning tops on the plane of the Solar System, while Uranus rotates more like a tilted rolling ball. Near the time of Uranian solstices, one pole faces the Sun continuously while the other pole faces away. Only a narrow strip around the equator experiences a rapid day-night cycle, but with the Sun very low over the horizon as in the Earth’s polar regions. At the other side of Uranus’s orbit the orientation of the poles towards the Sun is reversed. Each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness.[49] Near the time of the equinoxes, the Sun faces the equator of Uranus giving a period of day-night cycles similar to those seen on most of the other planets. Uranus reached its most recent equinox on December 7, 2007.[50][51]

    One result of this axis orientation is that, on average during the year, the polar regions of Uranus receive a greater energy input from the Sun than its equatorial regions. Nevertheless, Uranus is hotter at its equator than at its poles. The underlying mechanism which causes this is unknown. The reason for Uranus’s unusual axial tilt is also not known with certainty, but the usual speculation is that during the formation of the Solar System, an Earth sized protoplanet collided with Uranus, causing the skewed orientation.[52] Uranus’s south pole was pointed almost directly at the Sun at the time of Voyager 2′s flyby in 1986. The labeling of this pole as “south” uses the definition currently endorsed by the International Astronomical Union, namely that the north pole of a planet or satellite shall be the pole which points above the invariable plane of the Solar System, regardless of the direction the planet is spinning.[53][54] A different convention is sometimes used, in which a body’s north and south poles are defined according to the right-hand rule in relation to the direction of rotation.[55] In terms of this latter coordinate system it was Uranus’s north pole which was in sunlight in 1986.”

  25. “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.”

    Things may get very hot or very cold and it may take thousands of years to get back to ‘normal’, whatever that may be, but there are no tipping points.

    I believe Lubos’ article on Le Chatelier’s principle and climate would be an interesting read for these people: http://motls.blogspot.com/2007/11/le-chateliers-principle-and-natures.html

    From this article:

    “But the idea that positive feedbacks dominate or that they are the ones who win at the end simply contradicts basic laws of thermodynamics.”

  26. >>DOH !!!!!!!!
    >>Tired of hearing “Tipping Point” !!!!!!!!!!
    >>Should be banned from language !!

    Take heart with this. We’ve already passed one “tipping point” without evidence that anything tipped over. However, the THEORY of AGW has leaned a little more (kind of like the Leaning Tower of Pisa), and they still keep predicting more climate tipping points. One day the theory will fall all the way over no matter what they do to keep it propped up.

    I think these “tipping points” are actually an unconscious projection by the global warming faithful about what is happening to their cherished belief system. That’s how it works with deluded people.

  27. Remember what happened the following year 2008?The ice came back with vengance.The the global warming crowd was trying to disprove the ice report by saying it was a glitch in the system.When the ice increases ,as is doing ,they want to say it thin ice or young ice.

  28. And in the accompanying “Arctic Sea Ice Concentration” graphic, why are areas beyond the Arctic Circle included—particularly Hudson Bay, the Sea of Okhotsk, the Bering Sea, and the Gulf of Saint Lawrence?

  29. Dave Springer says:
    September 21, 2011 at 3:39 am
    /////////////////////////////////////////////////////
    As I have commented many many times, climate scientists never seem to look at history. For example, just consider the Viking settlements on Greenland and what that tells us about temperatures in high northern latitude, and ice/glacial extent 9a soewhat topical matter given the latest edition of the Times Atlas)..

    Further, it is almost certainly the case that the climate must self regulate, if not, we would not be here today (some 4.5 billion years after the formation of the Earth) given the varied and tumultuous past history of the Earth (eg., a core substantially hotter than today, extremely active volcanos, bombardment by asteroids, comets, may be even a snowball Earth, may be even an Earth with no ice at the poles etc. etc);. It is clear that planet Earth is one hell of a survivor. As such, it is extemely improbable that there are any irreversible tipping points (at any rate not within reasonable bounds).

    It is startling how cliamte scientists rediscover the wheel and may only just have appreciated that water will freeze when it gets cold enough no matter how hot the water may have been in the past. They could have averted the need to explore this issue by way of supercomputer and fiendishly sophsticated models simply by boiling a kettle, pouring the boiling water into a cup, putting the cup in the freezer, waiting a few hours and hey presto, you guessed, we have ice. After all this is one of the ‘settled science’ properties of water,

    I guess that commonsense is too much to expect. I wonder how much CO2 was emitted consequential to that research and the publicaton of the paper.

  30. What annoys me most are the blocking patterns which allow arctic outbreaks, and drain the pole of all its bitter cold. Then not only do I freeze my -bleep- off, but I have to listen to Alarmists gloat that it is “warmer-than-normal” at the pole.

    I prefer today. Nice pool of cold air stuck; smack, dab over the pole. Up there it is minus fifteen (C) which is an anomoly of nearly minus twenty (F.) Alarmists sulking as everything freezes up, up there, but nice and balmy in my back yard, in southern New Hampshire.

    But now I suppose they’ll switch the subject and get all alarmed about it being above normal in southern New Hampshire. Well, I”ll not let them spoil a golden day. If they change the subject I’ll change the channel.

    Actually that wouldn’t be a half-bad bumper sticker:

    Fight Global Warming.
    Turn Off The News.

  31. Werner Brozek says:
    September 21, 2011 at 8:26 am
    “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.”

    Things may get very hot or very cold and it may take thousands of years to get back to ‘normal’, whatever that may be, but there are no tipping points.

    I believe Lubos’ article on Le Chatelier’s principle and climate would be an interesting read for these people: http://motls.blogspot.com/2007/11/le-chateliers-principle-and-natures.html

    Unfortunately Lubos misapplies Le Chatelier’s Principle, whether he doesn’t really understand it or is just doing so deliberately I know not.

  32. Sigh, Studies like this again relying on models, are meaningless. You program into the model the accepted parameters and the expected outcome is arrived at based on that.

    Lets say you create a model of the stock market. It is not really any more or less chaotic then the eco system. Would you do what the models suggest you do? I do model things and I sure would not. Modeling helps to describe what might happen or does happen but by golly it is hard to get it right. If a prediction occurs within a range of +-5% I am stoked!

  33. I wonder how many taxpayer, if any, think that they are getting good value for their tax dollars fundng such “studies”. I can assure you I think we are being robbed. It is a license to steal.

  34. Innocent says:
    September 21, 2011 at 11:51 am
    Sigh, Studies like this again relying on models, are meaningless. You program into the model the accepted parameters and the expected outcome is arrived at based on that.

    Lets say you create a model of the stock market. It is not really any more or less chaotic then the eco system. Would you do what the models suggest you do? I do model things and I sure would not. Modeling helps to describe what might happen or does happen but by golly it is hard to get it right. If a prediction occurs within a range of +-5% I am stoked!

    1 – Models are computer programs. Computer programs do what they are programmed to do. If a model outputs certain results, that’s because that’s how the model was programmed.

    2 – Models do not output data. Models do not output facts.

  35. Ok, time for a stupid question. Given that the Arctic ice does disappear completely, what are the real-world consequences? Not the hyperbolic “end of the world” stuff, but expected value predictions?

  36. Tipping Point thinking:
    “OK, there’s no monster under the bed right now. But sometime soon there might be!”

  37. “Phil. says:
    September 21, 2011 at 10:01 am

    Werner Brozek says:

    Unfortunately Lubos misapplies Le Chatelier’s Principle, whether he doesn’t really understand it or is just doing so deliberately I know not.”

    Trust me, Lubos completely understands Le Chatelier’s Principle and I do as well. (I have an engineering degree.) We know how it applies to basic chemical systems when a single variable such as temperature, pressure, and concentrations changes. However indications are that it applies to climate as well.
    To give two concrete examples, according to how much CO2 man is putting into the air every year, only half shows up in the atmosphere. That is because photosynthesis uses more than normal and much CO2 gets dissolved in the oceans.
    Then Earth’s temperatures are not rising nearly as fast as the models believe they ought to be. That is because the feedbacks due to clouds are negative and not positive.
    Furthermore, Earth has been around for 4.5 billion years and it is very suitable for life right now.
    So I agree that while Le Chatelier’s Principle basically just applies to simple systems, I believe a much more complicated set of Le Chatelier’s types of Principles could be developed for climate, but we are not there yet. Many pieces of the puzzle are still missing, but papers like SB11 fill in some of the pieces.

  38. I’ve lost the link, but I read once of three polar expeditions, in the years 1822 – 1870, collectively seemed to document the partial loss and reformation of the Arctic icecap. Does this ring any bells with anyone? I’d like to know more about what they observed.

  39. I am SOOOOO glad they discovered this. Once, when I was at band camp, I took the ice cube tray out of the freezer and the ice all melted, so I threw the ice cube tray away.

  40. Dave Springer says:

    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.

    Wow, Dave. You really knocked the heck out of your strawman there! Of course, scientists have never said it can never come back. The question has always been to what degree there is hysteresis, so if, for example, temperatures heated up and then returned to present values, would the arctic ice recover to current levels (and how quickly)…Or does it require cooling to lower values to re-establish the ice at current levels?

  41. Once it gets hot enough to destroy man and in the series after man, the temp. will drop back and the ice will refreeze. Yes, Hansen will get his return of the ice age of 1977. Too little CO2 will destroy the planet, wait a second, heat is going to. Hum, maybe everything will evolve some more? Darn, I am confussed…….. :-(

  42. Let’s hope that the Earth doesn’t revert to its Neoproterozoic state of Snowball or Slushball Earth (does ice have a memory?). In fact, a readible and sensibly-written Wikipedia article (sorry, but I was rushed, and actually the article is quite good):

    http://en.wikipedia.org/wiki/Snowball_Earth

    describes a relatively new line of thought that suggests we might have far more to fear from cooling than we do from AGW, to wit: “…The idea is that Earth’s carbon-based life forms affect the global carbon cycle and so major evolutionary events alter the carbon cycle, redistributing carbon within various reservoirs within the biosphere system and in the process temporarily lowering the atmospheric (greenhouse) carbon reservoir until the revised biosphere system settled into a new state. The Snowball I episode (of the Huronian glaciation 2.4 to 2.1 billion years) and Snowball II (of the Precambrian’s Cryogenian between 580 – 850 MYA and which itself had a number of distinct episodes) are respectively thought to be caused by the evolution of aerobic photosynthesis and then the rise of more advanced multicellular life and life’s colonization of the land.[74][75]…”

    We’re down so low in CO2 content of the atmosphere that colder climate is probably much more likely than warmer (can anyone definitively state that the Quaternary Ice Age is over?). Perhaps Trenberth’s great (unseen, unmeasured but model-proven) deep-sea warmth accumulation will rise up to save us. LOL

  43. @Joel Shore

    Good to see you posting again.

    Strawman? I believe Dave Springer was accurately commenting on this point in the article: “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.” (bold mine)

    I had similar thoughts as Mr. Springer.

  44. charles nelson says:
    September 21, 2011 at 6:34 am

    Irreversible!! Irrepressible more like.
    I invite everyone to look at those amazing NOAA Arctic timelapse sequences of freeze and thaw…watch especially the rushing currents transporting ice into the oceans and the ease with which it is replenished. …it should be quite obvious to anyone that the Arctic can and will keep pumping out ice until the earth shifts on its axis and there is no longer 3 months of sub-zero darkness.

    You’ve got a good point, Charles. Wouldn’t it have been easier just to take a bucket of seawater, put it in a deep freeze for three months with the door shut and see if it turns to ice? They would have saved a whole bunch of CPU cycles.

  45. To think that humans have anything to do with global climate is absurd. The only differences are in a parking lot in open sun in July. We need to bring back Mr. Bill “Oh Noooooooooooooooo”

  46. Joel Shore says:
    September 21, 2011 at 6:31 pm

    …Or does it require cooling to lower values to re-establish the ice at current levels?

    You’d start to get sea ice the moment the surface temperatures in the Arctic caused the seawater at the suface to go below the freezing point of seawater. It would grow proportionally to the amount of heat removed. History at that point is totally moot–fantatsical–mythical.

    Sea ice does not have a memory, and by the same token, seawater doesn’t have a memory either. This “tipping point” you refer to doesn’t apply–seawater isn’t some mechanical contraption; we’re talking about freezing water here.

  47. Not really. There is no reason based on this for emission reduction or anything else. Leaving aside the obvious facts that warmer is better for the environment as is increased carbon dioxide, this entire paper is based on the reactions of a model. The reactions of the model are not indicative of the real world in any way, In other words this is a waste of paper.

  48. H. R. says:

    Strawman? I believe Dave Springer was accurately commenting on this point in the article: “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.” (bold mine)

    I had similar thoughts as Mr. Springer.

    Well, perhaps they were not as clear as they could have been…but the point is that they were talking about there being a hysteresis effect, so as it says, when you lower the temperature back down to a certain point, the ice doesn’t necessarily assume the same extent it did when you were at that temperature on the way up. You might want to look at a hysteresis curve for magnets to understanding the concept here: http://en.wikipedia.org/wiki/Hysteresis

  49. @Joel Shore says:
    September 22, 2011 at 10:47 am

    Agreed… they weren’t clear at all in that quote and it did tend to make one’s head snap back that they’d say such a thing. (Who knows why they’d say something that daft.) So… many here had a little (a lot!) of fun with that.

    Yup, I understand the hysteresis thingy having to work with it and around it on a daily basis. Of course the ice would return when it’s cold enough but I would think that it would be slower to re-establish the arctic ice if it ever were to actually become ice free. The various currents would have their way with the baby ice until the ice could get firmly established. And if humans and ice breakers are still around at such a time, I’m sure they’d work like the dickens to keep the ice from re-forming. There’s a lot of value in an ice-free Arctic Ocean!

  50. RockyRoad says:

    You’d start to get sea ice the moment the surface temperatures in the Arctic caused the seawater at the suface to go below the freezing point of seawater. It would grow proportionally to the amount of heat removed. History at that point is totally moot–fantatsical–mythical.

    Sea ice does not have a memory, and by the same token, seawater doesn’t have a memory either. This “tipping point” you refer to doesn’t apply–seawater isn’t some mechanical contraption; we’re talking about freezing water here.

    It is probably a cleaner experiment to talk about lowering the greenhouse forcings back to the original level than the temperature back down to the original level. In that case, some hysteresis is indeed possible because an earth with more ice coverage will tend to reflect more of the incident solar radiation than an earth with more ice coverage. So, yes, there is the possibility of more than one metastable state existing for a certain level of greenhouse gases. (A dramatic example of this that may have occurred in the past is the transitions back-and-forth between iceball or slushball climates and warmer climates.)

    With temperature, the arguments are a bit subtler…but I think it is still possible to have the same global temperature but have the distribution be different. Or, as H.R. notes, the various currents could be different.

    But, again, like I said, it is probably easier to visualize hysteresis occurring in the context of bringing the greenhouse gas forcings back down to the original level rather than the temperature back down to the original level.

  51. Vaguely related. The North Pole cam image suddenly showed a current image today but there is not much to see. It appears, as I suspected, the cam is now buried in snow / ice.

  52. @Joel Shore

    “[...]
    But, again, like I said, it is probably easier to visualize hysteresis occurring in the context of bringing the greenhouse gas forcings back down to the original level rather than the temperature back down to the original level.”

    I tend to visualize the ice core data where CO2 levels lag temperature changes by 800ish years. The input stops and the response continues for a bit.

  53. OK, the cam is not buried yet. It was iced over. The ice is now sublimating away. Nice sunset underway but can’t see too much.

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