Sea ice: vapourware

Via their blog, Nurture have some commentary on sea ice by Serreze & Stroeve.

Its all pretty vapid: With sharply rising atmospheric greenhouse gas concentrations, the change to a seasonally ice-free Arctic Ocean seems inevitable. Very good, but The only question is how fast we get there. Well its certainly an important question, but the most important point is that they have no answer.

After the resulting record-low ice extent in September, unprecedented in satellite observations, over 70 per cent of the sea ice cover in spring 2008 consisted of young, fairly thin ice — an even more extreme situation than in spring 2007. The eyes of the science community and fascinated citizens worldwide were therefore focused on 2008. Would there be a new record minimum in September of 2008, suggesting the start of a rapid slide, or would there be some recovery? Indeed, its good to remember that a lot of the predictions of a record min for this year were based on the fact that much of this years ice was first year, and so would melt away more easily than last year. It didn’t happen quite like that; there are lots of complex factors. This year there will be a bit more multi-year ice: perhaps the beginning of a recovery? Naturally enough S+S don’t discuss that possibility.

No-one knows if there will be more or less ice next year. Personally I think, on balance, that the 2007 record is unlikely to be broken, and have offered to put my money on it. Or at least some, unspecified amount: I haven’t refused any offers yet, not that I’ve exactly been inundated with takers. I wonder if “Standing on the brink” S+S are willing to put their money where their insinuations are?

I don’t believe the assertions that recent years are good evidence of acceleration; indeed, I think its quite likely that the IPCC model consensus is correct. Somehow the meme that the world is well ahead of these model predictions has become dominant. But 2007 was obviously exceptional; to a less extent 2008 was too. Lets not get too carried away on the basis of one or two years.

Comments

  1. #1 Steve L
    2008/10/10

    You don’t seem to think we can get pushed ahead of schedule by an exceptionally extreme year. I think I would agree with you in this case, especially since the minimum of sea ice extent occurs so long after the summer solstice. But don’t you think that, if Arctic sea ice was exceptionally low early enough in the summer, and the skies were clear, that the increased absorption of solar energy could advance the schedule, so to speak? I guess the question I’m trying to ask is about positive feedbacks and whether an exceptional year (regardless of what produces it) can put us markedly ahead of projections.

    [I can admit what you suggest as a theoretical possibility. My own modelling work (Schroeder, D., and W. M. Connolley (2007), Impact of instantaneous sea ice removal in a coupled general circulation model, Geophys. Res. Lett., 34, L14502, doi:10.1029/2007GL030253.) suggests otherwise, though: the ice recovers very quickly from imposed anomalies -W]

  2. #2 John McCormick
    2008/10/10

    William, you are getting too carried away on the basis of one or two years.

    Those of us looking at the post 1979 record see trends you are not willing or unable to see.

    Depite your thin treatment of thin (first year) ice the facts speak for themselves. Forst yeara ice will melt soonest, fastest and open ocean will release heat and wave action to melt more ice.

    It is not — never has been — about records. It is all about greater expanse of new ice giving way to wave action and warmer ocean temp pushing further towards the western Greenland coast.

    John McCormick

  3. #3 Eli Rabett
    2008/10/10

    Basically John McCormick’s point but your

    But 2007 was obviously exceptional; to a less extent 2008 was too.

    is cutting it REALLY thin. The difference was very small.

    [Well yes, as I’ve said -W]

    When we made our original bet you thought that previous trends would return the minimum ice area to baseline conditions and that 2007 was a one off. I, on the other hand figured it was a coin flip because the 2007 melt imposed a memory condition on 2008. Since 2008 was essentially the same as 2007 the same is true for 2009.

    [Close. I don’t think I ever said “baseline conditions”, since I’m not sure what they might be. If I believed in recorvery to straight line extrapolation, I’d have to be predicting about 7M for JAS, according to http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seasonal.extent.1900-2007.jpg I’mnot that brave -W]

    Given the hysteresis effect that young winter ice imposes on melt it is reasonable to suppose that we will only return to the previous conditions (straight line extrapolation) if there is a fairly large volcanic explosion in the northern hemisphere that allows multiyear ice to form

  4. #4 Gareth
    2008/10/10

    As we went “double or quits”, you do have a bet.

    [Yes I know. I have two so far. But thats not exactly inundation -W]

    Otherwise, what Eli said.

  5. #5 Brian Schmidt
    2008/10/10

    Seems to me that the increase in CO2 levels is the more obvious threat to the IPCC consensus (or at least pushing to the high and more dangerous end of the consensus range).

  6. #6 Steve L
    2008/10/11

    Thanks W for your reply to my comment. Very interesting.

  7. #7 Steve L
    2008/10/13

    Is it worth pointing out that the recovery of sea ice in your modeling experiment was observed under pre-industrial conditions? I only read the abstract of the paper:
    “A control run is chosen as reference experiment with greenhouse gas concentration fixed at pre-industrial conditions.”
    Perhaps the change in conditions from pre-industrial times makes for a difference as to whether we see the rapid recovery observed in the model output.

    [Thats true, but we don’t think its relevant. Climate is pretty well stationary over the few years timeframe we looked at -W]

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