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Sea ice minimum forecasts

Filed under: — gavin @ 17 July 2009

One of the interesting things about being a scientist is seeing how unexpected observations can galvanize the community into looking at a problem in a different way than before. A good example of this is the unexpectedly low Arctic sea ice minimum in 2007 and the near-repeat in 2008. What was unexpected was not the long term decline of summer ice (this has long been a robust prediction), but the size of 2007 and 2008 decreases which were much larger than any model had hinted at. This model-data mismatch raises a number of obvious questions – were the data reliable? are the models missing some key physics? is the comparison being done appropriately? – and some less obvious ones – to what extent is the summer sea ice minimum even predictable? what is the role of pre-conditioning from the previous year vs. the stochastic nature of the weather patterns in any particular summer?

The concentration of polar expertise on the last couple of questions has increased enormously in the last couple of years, and the summer minimum of 2009 will be a good test of some of the ideas that are being discussed. The point is that whether 2009 is or is not a record-setting or near-record setting minimum, the science behind what happens is going to be a lot more interesting than the September headline.

In the wake of the 2007 minimum, a lot of energy went in to discussing what this meant for 2008. Had the Arctic moved into a different regime where such minima would become normal or was this an outlier caused by exceptional weather patterns? Actually this is a bit of false dichotomy since they aren’t exclusive. Exceptional patterns of winds are always going to be the proximate cause of any extreme ice extent, but the regime provides a background upon which those patterns act. For instance, in the paper by Nghiem et al, they showed the influence of wind patterns in moving a lot of thick ice out of the Arctic in early 2007, but also showed that similar patterns had not had the same impact in other years with higher background amounts of ice.

This ‘background’ influence implies that there might indeed be the possibility of forecasting the sea ice minimum a few months ahead of time. And anytime there is the potential to make and test predictions in seasonal forecasting, scientists usually jump at the chance. So it proved for 2008.

Some forecasting efforts were organised through the SEARCH group of polar researchers, and I am aware of at least two informal betting pools that were set up. Another group of forecasts can be found from the Arctic ice forecasting center at the University of Colorado. I personally don’t think that the intrinsic worth of a successful prediction of overall sea ice extent or area is that societally relevant – interest in open shipping lanes that might be commercially important need much more fine-grained information for instance – but I think the predictions are interesting for improving understanding of Arctic processes themselves (and hopefully that improved understanding will eventually feed into the models and provide better tests and targets for their simulations).

What was particularly interesting about last years forecasts was the vast range of forecasting strategies. Some were just expert guestimates, some people used linear regression on past data, some were simply based on persistence, or persistence of the trend. In more mature forecasting endeavours, the methods tend to be more clustered around one or two proven strategies, but in this case the background work is still underway.

Estimates made in June 2008 for the September minimum extent showed a wide range – from around 2.9 to 5.6 M km2. One of the lowest estimates assumed that the key criteria was the survivability of first year ice. If one took that to be a fixed percentage based on past behaviour, then because there was so much first year ice around in early 2008, the minimum would be very low (see also Drobot et al, 2008). This turned out not to be a great approach – much more first year ice survived than was predicted by this method. The key difference was the much greater amount of first year ice there was near the pole. Some of the higher values assumed a simple reversion to trend (i.e. extrapolation forward from the long-term trend to 2008).

Only a couple of the forecasts used physics-based models to make the prediction (for instance, Zhang et al, 2008). This is somewhat surprising until one realises how much work is needed to do this properly. You need real time data to initialise the models, you need to do multiple realisations to average over any sensitivity to the weather, and even then you might not get a range of values that was tight enough to provide useful information.

So how did people do? The actual 2008 September minimum was 4.7 M km2, which was close to the median of the June forecasts (4.4 M km2) – and remember that the 2007 minimum was 4.3 M km2. However, the spread was quite wide. The best estimates used both numerical models and statistical predictors (for instance the amount of ice thicker than 1m). But have these approaches matured this time around?

In this year’s June outlook, there is significantly more clustering around the median, and a smaller spread (3.2 to 5.0 M km2) than last year. As with last year, the lowest forecast is based on a low survivability criteria for first year ice and I expect that this (as with last year) will not pan out – things have changed too much for previous decades’ statistical fits on this metric to be applicable. However, the group with the low forecast have put in a ‘less aggressive’ forecast (4.7 M km2) which is right at the median. That would be equal to last year’s minimum, but not a new record. It would still be well below the sea ice trend expected by the IPCC AR4 models (Stroeve et al, 2008).

There is an obvious excitement related to how this will pan out, but it’s important that the thrill of getting a prediction right doesn’t translate into actually wanting the situation to get worse. Arctic ice cover is not just a number, but rather a metric of a profound and disruptive change in an important ecosystem and element of the climate. While it doesn’t look at all likely, the best outcome would be for all the estimates to be too low.

858 Responses to “Sea ice minimum forecasts”

  1. 1
    Knut Witberg says:

    To me it looks like that the thaw in summer is rapid and obviously more extensive than earlier years with satellite observations.

    But the freezing in late autumn and winter is also very rapid. The temperatures are not that high – this year the temperature went over 0C later than any other year in the last 50 years.

    Can it be that the black carbon soot from millions of cooking fires in India, coal power stations in China, thousands of forest fires in Indonesia and so on.

    With other words: The thaw is rapid when the black soot shows up and increasingly so in the summer. When the sea ice becomes covered by snow its is not a dominant driver for the melting of sea ice. Therefore the rapid re-freezing of the sea-ice in the late autumn and winter.

  2. 2

    Nice post. Readers might also want to take a look at NSIDC’s Sea Ice News and Analysis site ( Here you will find the blow-by-blow account of the changing sea ice cover. We have daily updated maps and time series of ice extent, and discussion pieces on a monthly basis for much of the year, transitioning to bi-weekly and weekly pieces as we approach the seasonal minimum in September. Lots of good high res. figures as
    well. Taking a look at the updated graph, you’ll see that as of yesterday, we were well below climatology, and a bit above 2007.

  3. 3
    Jeffrey Davis says:

    My memory of 2007’s record is that it had been augmented by unexpected wind patterns. Has the change become a fixture of the Arctic or have winds reverted to more traditional patterns?

  4. 4

    #2 Mark, Excellent report from NSIDC, fascinating that the pressure situation was similar to 2007 yet the melt not as strong. They left out the present dominant clouds cover, which is the main difference with 07. Their final estimate is likely, 07 record will likely not be broken, but I add 08, having similar cloudy conditions at this time, but not the synergistic High pressure exacerbating the Arctic Ocean gyre current stronger towards the Atlantic, therefore 09 will exceed 08 shaving close to 2007 minima. I make another prediction, if El-Nino persists grows and vanishes mid spring 2010, sailing will be possible from Bering strait to Spitzbergen via the Pole come September 2010.

  5. 5
    Mark says:

    “But the freezing in late autumn and winter is also very rapid.”

    Yes, because the freezing depends on how long the sun goes away for. And that depends on orbital mechanics, not CO2.

    After all, if there’s no sun for 4 months, it will get freezing toward the end. Even if CO2 adds 10C to the temperatures. After all your coffee gets cold in the best thermos ever built by man in less than 4 months.

  6. 6
    Mark says:

    PS so we have vey much the same maximum extent of ice in winter. But summer has heat coming in, which CO2 can retain a little better. So we have a much smaller summer extent.

    Going from a smaller summer extent to the same winter extent rather does require quicker growth, doesn’t it? After all, if the summer ice hadn’t melted, the extra winter ice being laid down would no longer appear as new ice and so would not contribute to growth of ice extent.

  7. 7
  8. 8
    Mark Zimmerman says:

    The link to the Nghiem study appears to be broken

    [Response: Fixed. Thanks – gavin]

  9. 9
    Petro says:

    I think the main reason for the Arctic sea ice obsession is that it is considered as the first sign of irreducible climate change. Besides, it can be relatively soon, that the Arctic sea has no ice in summer, which is surely unpredicted in the beginning of this millenium.

    No one seems really know, what it means that there is no ice cover on the Arctic during summer. There was a study, that less sea ice increases the temperature a centigrade or two up to 1500 km from the ocean and speculations that sea currents and wind patterns change have arised. Maybe you could write a post on the topic here in RealClimate?

  10. 10
    Steve Milesworthy says:

    Purely as a spectator, while last year’s June projections looked quite good, the May ones were way off – predicting a more dramatic loss. In the end, the melt matched the median of the June predictions. But this followed a much more rapid melt during mid-August to early-September than had occurred in the previous few years – was it luck or skill!?

  11. 11

    Normal statistics isn’t the best way to predict extreme values and thirty years is a relatively short time to be making accurate climate predictions. Extreme value statistics should be based on lots of data over longer time periods. Said that I’m still game to join many others in making predictions using normal statistics. I’ve found very strong correlations between Scripps carbon dioxide data, sea ice extent, and Arctic SST. Besides the annual cycles, the data show cycles common to all three with wave lengths around 9 and 308 years. I welcome all to view my analysis at I’ve found that the Scripps data is probably our best measure of climate change and is a strong function of both sea ice extent and and Arctic SST. The Mauna Loa and South Pole daily flask data go back to 1960 and 1957 respectively. This week I have critically analysed the raw data and developed statistical fits that produce better than three 9s for R square. The most significant parameter is a 322.5 year sine wave. This wave has a minimum of 312 around 1940 and a maximum of 500 around 2100. None of us are likely to stick around to see it but we can watch the trend. The rate of accumulation is starting to decrease rather than increase exponentially with anthropogenic increasing emissions.I strongly believe that decreasing those emissions by any amount will have no measurable effect on that trend.

  12. 12
    Lynn Vincentnathan says:

    According to the IPCC AR4 chart it looks like the ensemble mean going below 5.0 wasn’t predicted until around 2050.

    This seems to be another case of “it’s worse than we thought.” I’m just wondering if “it’s worse than we thought” is stochastic random variations, or there’s some upward trend here.

  13. 13
    Doug Bostrom says:

    Petro 17 Jul 2009 at 11:14 am

    “No one seems really know, what it means that there is no ice cover on the Arctic during summer.”

    That does seem like a great topic for modeling with a specific objective in mind, particularly if it could done repeatedly over a continuum of ice cover.

  14. 14
    Chris G says:

    Thoughts from a layman.

    Arctic sea ice is an obsession for me for a couple of reasons.

    It is so huge that its own mass and latent heat would seem to act as a buffer against high variability. That is, changes in it year over year would reflect a summation of forces acting upon it, and so, random fluctuations tend to cancel each other out more so than temperature readings at any specific locale, or most other measurements. (Nevertheless, it still shows a lot of variance.) It’s also easier to measure than the mass of the major ice sheets (well, extent more so than thickness) and I believe it has more interaction with the rest of the world because it is in contact with the ocean currents. It probably has more variability than biological changes, like changes in the distribution of species or migratory timings, but it is harder to point an instrument at those and get a reading.

    The feedback mechanism of melting ice is rather large as well. So, I tend to see changes in it as an indicator of whether the IPCC predictions are more or less below or above the mark for the rate of change, as well as the rate of change of the rate of change. I presume nonlinear effects because of feedback mechanisms, and also because the records of the ice cores makes it look like the climate system has at least 2 modes of relative stability and the transition from one to the other can be rapid. I wonder if the increase in CO2 will drive us into a mode we haven’t seen before, or have good records of, or if it will simply drive us a bit higher in the current mode.

  15. 15
    Andy Revkin says:

    Lots more on the complex mix of factors determining trends in sea ice — and the many efforts to untangle them:

  16. 16
    Aber says:

    The threat to the Arctic is known for quite some time. C.E.P. Brooks regarded it “of great significance in human affairs” in 1938 (Met.Magazine, p.29-32. When Al Gore’s paid the North Pole a visit by submarine before becoming Vice President of the U.S.A he observed: “We were crashing through that ice, surfacing, and I was standing in an eerily beautiful snowscape, windswept, and sparkling white, with the horizon defined by little hummocks, or ‘pressure ridges’ of ice that are pushed up like tiny mountains ranges when separate sheets collide. But here too, CO2 levels are rising just as rapidly, …As the polar air warms, the ice here will thin; and since the polar cap plays such a crucial role in the world’s weather system, the consequences of a thinning cap could be disastrous” (Al Gore, ‘The Earth in Balance’, 1992. However, a brisk Arctic warming started in the late 1910, and it is still unknown why and how it commenced.

  17. 17
    MJ Strong says:

    Looking at the NSIDC ice extend and area charts…both 2008 and now 2009, have, month by month, been above the 2007 meltdown. In actually retrieving ALL of the data points from the NSIDC files available on-line, GLOBAL sea ice has an absolutely flat trend-line over the 30 years of satellite data. So although the Arctic has a negative slope trend for this period, the Antarctic has an equal and opposite offset. The fact that there was little “multi-year ice” in 2008 and 2009, I think it is pretty amazing that the Arctic faired well last summer and now.

    One other issue is the fact that the NSIDC always compares to the 1979-2000 average. Calculating the mean by using only the first 20 years out of 30 years of data basically throws out 30% of the mean calculation.

    The other issue is the trendline numbers and slope posted under the NSIDC monthly ice area and extent charts. Their tren numbers are not “per decade” as noted on the chart. It seems to be the trend from month to month, not per decade (that is, each month the numbers change quite a bit such as -3.4, -1.1, then the next month it is -2.2 …which is impossible if the trend line is a plot over the three decades. This just doesn’t show up to match what they are saying about the trend when you plot it, as I did, using a simple EXCEL chart plot and auto-generated trendline graph.

    A final comment about the monthly plots. The Antarctic plots they show of monthly ice averages have changed radically since December 2008. In overlaying the latest charts of the last 30 years of data points from month to month, the NSIDC charts are never the same as if there is some sort of glitch in the plotting equation. Some month plots over the past 6 months had totally opposite data points when compared with the database. I have complained about this to the NSIDC at least on three occassions and FINALLY, this month, it looks closer to what I get when I plot the entire data set (making up for a number of totally missing” months of data from Dec 1987 and Jan 1988). At best, this is a bit sloppy in their record-keeping.

    Believe half of what you see from the NSIDC ice charts and the faulty satellite sensors which disagree with the Arctic ROOS Data.

  18. 18
    Mark Zimmerman says:

    Is anyone aware of documentation of Arctic wind anomalies similar to 2007 (Polar Express) in years prior to the current decade?

  19. 19
    Jim Bouldin says:

    Thanks Gavin and also Mark Serreze. A couple of questions:

    1) What is the current/recent state of the NAO (per the discussion of its possible influence, via wind, in the early 90s)?
    2) Is it related in a known way to the pressure gradient two years ago that drove the southerly air flow and strong melt?
    3) Are either of these in turn related in a known way to the PDO or ENSO?
    Thank you.

  20. 20

    Thanks for a fascinating post! Why is it that watching the ice melt is so much more interesting than watching paint dry, even though it’s far slower?

    Let me renew my offer to share an Excel sheet I did up on the IJIS sea ice extent data. It’s a convenience for anyone who wants to follow that data in near real-time without the hassle of formatting from scratch. Just click on my name in the message header to reach my website. (If that doesn’t work, it’s

    Remember, though, it’s not guaranteed to help if you enter any of those betting pools.

  21. 21

    Also–and I’m only putting this OT link on this post because I’m not seeing any “recent comments” in the sidebars–here’s a technology for solar electrical generation that I’ve not seen before:

    It’s interesting that “commercial-scale” deployment is expected next year, but it would be nice to have some actual numbers, both in technological and economic domains.

  22. 22
    dave p says:

    Re#4 the NSIDC map seems to show considerably less ice loss than the UIUC and Bremen Univ. maps. Therefore their ice loss graph seems to be an underestimate. Has anybody else noticed this?

  23. 23
    dhogaza says:

    Believe half of what you see from the NSIDC ice charts and the faulty satellite sensors which disagree with the Arctic ROOS Data.

    Interestingly, a few months ago the WUWTer favorite chart was from IJIS, which uses the AMSRE sensor from another satellite. Then, when NSIDC recalibrated to the sensor on NOAA-17 (IIRC) and started agreeing closely with the IJIS results (as their numbers do now), suddenly IJIS fell out of favor with that bunch, and here they are spewing that now Arctic ROOS is the accurate source. Why? Because at the moment they’re showing higher ice extent figures than IJIS and NSIDC.

    Gee, guys, cherry-pick much?

  24. 24
  25. 25
    David B. Benson says:

    Knut Witberg in comment #1 suggests black carbon. That was my thought while reading this thread. Is there any “black carbon index” available?

  26. 26
    wili says:

    I would like to join Petro (#9) and Doug B (#13) in pleading for models, opinions, speculations, WAGs… on what may be the short- and long-term effects of an ice-free late summer Arctic Ocean on northern hemispheric and global climate.

    I imagine direct some direct effects may happen sooner (or are already happening with an increasingly if not completely ice free Arctic?), while indirect effects–from consequent changes in ocean currents…–may take longer.

    Also, is the focus on ice cover a bit misplaced? I know it plays a role in albedo feedback, but isn’t total ice mass the most important stat to be following? As others have noted here and elsewhere, ice mass and average ice thickness loss has continues, even though ’08 was not as dramatic a year as ’07 for reduction in total sea ice extent.

    With almost no 5+meter-thick ice left, what is the probability that this year could see the total dissolution of Arctic sea ice?

  27. 27

    From the last sentences of Gavin’s post:”Arctic ice cover is not just a number, but rather a metric of a profound and disruptive change in an important ecosystem and element of the climate. While it doesn’t look at all likely, the best outcome would be for all the estimates to be too low.”

    Though the low outcome would be desirable from this point of view,(as well as more favorable albedo numbers)estimates that are on target would seem to answer and/or correct for the questions posed in the first paragraph regarding predictability,pre-conditioning,data reliability,or possibly overlooking of some physics principle.

  28. 28
    Deep Climate says:

    NSIDC is a great resource, especially the perspective of 1979-2000 average. Here’s the URL for the actual graph:

    JAXA shows all recent years, and so is useful too.

    The latter shows 2009 just edging below 2008. (My prediction, made in haste at Stoat, was “closer to 2008 than 2007 or 2005”. Let’s call that 4.7 +- 0.2 M km2).

    I notice that the blogosphere was atwitter over spring Arctic sea ice anomalies. But the Jaxa graph shows that the June anomaly, say, is not indicative of sea ice minimum trend, as measured in Spetember. So it seems to me that trends in June sea ice extent are not particularly relevant. Maybe Mark S can give us the comparative trends by month.

    If you’ll permit a slightly OT segue, we have Lord Monckton:
    “There was almost certainly less Arctic sea-ice in the early 1940s than there is now, and there may have been none in Summer in the middle ages.”

    Meanwhile, we have Friends of Science advisor Tim Ball claiming:
    “The National Snow and Ice Data Center reports a
    continuation of the [Arctic] sea ice recovery.” (as of July, 2008).

    Lots of other presumably unintentional hilarity in this document, too.

    Now comes news FoS is co-sponsoring a Canadian speaking tour by Monckton this September, with apparent funding through the Science Education Fund at the Calgary Foundation (the same fund that supported Friends of Science until the University of Calgary pulled the plug).

  29. 29
    tamino says:

    Re: #17 (MJ Strong)

    In actually retrieving ALL of the data points from the NSIDC files available on-line, GLOBAL sea ice has an absolutely flat trend-line over the 30 years of satellite data

    This is so wrong it’s hard to imagine how anyone could make such a claim with a straight face. GLOBAL sea ice shows a distinct, strong, and statistically significant declining trend over the 30 years of satellite data.

    False claims about “trends” are becoming more shrill and more ludicrous; there are so many that constantly correcting them is becoming quite tiresome. Perhaps that’s the intent.

    But there is a commonality to them: the vast majority of ludicrous claims about trends come from those who deny the reality, human origin, and danger of global warming. Imagine that.

  30. 30
    James Staples says:

    Hmmmm. Being the guy who always reminds you to focus a little more on the possibility and consequences of a shut down of the North Altlantic Thermo-Haline, deep-ocean return circulation mechanism; I wonder if less sea-ice in the Arctic might not let the Gulf Stream penetrate into – and thus spend itself – the Arctic Ocean.
    I would like to see Real Climate, or anyone, do a study of Deep Arctic Ocean, cold, dense, desalinated current circulation paterns; or, at least, some more info about the state of the aforementioned ‘drain’ down which the Gulf Stream currently ‘flushes’, with regards to the effects that decreasing salinity of this return flow (due to Greenlands Ice melting) has been having upon it; as the news was not good in the 1990’s.

  31. 31

    Re #17, 1:11 PM: MJ, a couple of quick responses.

    The 1979-2000 average is not a running mean, but a baseline. It’s supposed to act as a stable benchmark. All the climate datasets are set up this way (though not necessarily with those particular years.)

    The monthly numbers “per decade” are, as you say, for the particular month only. However, you can have “a decade’s worth of Junes” (or Mays, or whichever month.) Breaking the numbers down this way makes it evident that the trend toward lower extents is greater at some times of year than others. (The minima are trending down much faster than the maxima, for instance.) NSIDC also provides annual trends stated “per decade,” so you can look at decadal trends for any month, or annually. You just need to be attentive which is which.

    As to the question of data points changing, I’m afraid you aren’t very clear exactly what is wrong–I can’t really tell what you mean by “totally opposite data points,” for example. But there are a couple of things to bear in mind. One is that data correction–quality control–continues for up to a year after the initial posting. Again, you’ll see this a lot in different datasets–for example, IJIS often adjusts their sea ice extent numbers after just a few hours. (That was the case today, actually.) Another thing that can affect the graph, at least, is the application of smoothing algorithms–such as moving averages–to the plot. It can appear to change the plot line “after the fact,” though it doesn’t change the actual data.

    Hope this helps!

  32. 32
    jcbmack says:

    I do not think you guys are missing key physics. I just think weather patterns and climate variability coupled with flucuating emissions have a lot to do with it, but the physics and chemistry is well established. I do think you guys hit high quality approximations and this is all one can expect from such a complex system. You will get closer and narrow the “spread.”

  33. 33
    jcbmack says:

    Oh and trends serve well, but even trends have great limitations on such short term and sudden changes.

  34. 34
    Mike Hilson says:

    It has occurred to me that as the extent and thickness of arctic sea ice declines, it becomes far easier for ice to drift southward through straits to the Pacific and Atlantic Oceans.

    In other words, when sea ice is bound tighter to northern land masses, it might tend to remain stuck, even under the influence of northerly winds. Conversely, when ice is broken up and flowing more freely, it will drift more easily out of the Arcic when winds are conducive.

    Does this make sense to any experts ?
    If so,is it factored into any models ?

  35. 35
    Bill Sneed says:

    Re: #19:

    You can probably answer #1 for your self with the data found here:

    Regarding #3, it’s been argued, see for example,
    that the NAO is the dominant recurring mode across the Arctic. Dominant is not exclusive so it’s probably safe to assume that there may be some relationship with the PDO and ENSO but I’ll leave that to others.

  36. 36
    MJ Strong says:

    Million sq. km global sea ice area (from year long average)

    18.07 (start in 1979)

    Average is 18.06

  37. 37
    John Monro says:

    Your links to the SEARCH group, the betting pools and Arctic Ice Forecasting Centre all work, but none of them have been updated since last year. Has interest, like the ice, evaporated a bit?

    The two sites I regularly visit, Cryosphere Today and NSIDC show the ice melt, after a slow start in April and early May, then tracking down quite nicely, in fact at one point melting to the same extent as in 2007 at the beginning of June. However a subsequent “slow” June makes if very unlikely that the ice will melt to near the 2007 extent, but it is still quite possible for the melt to exceed last year’s, it’s a bit of a race. I believe that temperatures in north-east Canada have been rather colder than normal, so this suggests that despite a low total ice amount, there will be more melt on the Russian Arctic seas than in the Canadian Archipelago, and the fabled North West Passage might not yet become fully navigable,

    So if I was a betting man, I’d go for the three predictions of Kauker, Petrovsky and Stroeve at 4.6 million sq kms. mainly because there’s so much thin first year ice that will melt in the next eight weeks, despite the lessening amounts of sunshine.

    It’s a fascinating area of study because if one could fully understand the physics of ice melt, albedo, atmospheric circulation etc in the Arctic, it must mean a much greater understanding of climate change science generally. It is also possible with the pace of change we’re seeing that the results of models can be demonstrated much more quickly. The fact that the IPCC models got things so wrong in the Arctic is a worry, because that’s what we’re basing our still very inadequate political and economic response to AGW on.

  38. 38
    Hank Roberts says:

    Re #17, MJ Strong, about global sea ice trend:

    Where did you get your information?

    Would you please point to your source?

    I don’t recognize you as a regular poster; if you’re new to this issue, remember to search the same keywords three ways and observe the difference in what you find, e.g.


    Google Images:

    Google Scholar:

    (I’m guessing your source is going to show up in one, two, or all three of those search results. That doesn’t mean it’s right or wrong, good or bad, honest or not, it just means Google found it.)

  39. 39
    Jacob Mack says:

    Melting ice at a faster rate is not good, but the correlation between AGW and less ice is as of yet to be determined. We need more research.

  40. 40
    Hank Roberts says:

    > Antarctic growing

    Someone knowledgeable can comment about this, I can’t beyond noting the prediction, based on the prediction of increased snowfall over the Southern Ocean as the climate changes:

    “… The observed increase in Antarctic sea ice cover is counter to the observed decreases in the Arctic. It is also qualitatively consistent with the counterintuitive prediction of a global atmospheric-ocean model of increasing sea ice around Antarctica with climate warming due to the stabilizing effects of increased snowfall on the Southern Ocean.”

    Published 16 May 2002.
    Zwally, H. J., J. C. Comiso, C. L. Parkinson, D. J. Cavalieri, and P. Gloersen (2002), Variability of Antarctic sea ice 1979–1998, J. Geophys. Res., 107(C5), 3041, doi:10.1029/2000JC000733.

    Google Scholar says 100 papers have subsequently cited the above; here they are:

  41. 41
  42. 42
    cougar_w says:

    If folks are still wondering what all the fuss is about RE Arctic melting, this might be of interest:

    Something nominally alive appears to have broken loose in the Arctic, perhaps from the bottom of the sea floor, or maybe from the bottom of the ice itself. It might also just be a floating mat of something that is normally afloat, but my experience with mats like this is they tend to break free of a substrate of some kind and then float as a unit until something (usually the wind) disrupts them. While the goo itself doesn’t appear to pose a problem (I’d not want to get any on my clothes, by the looks of it) the very fact of it existing at all in this location has people stumped.

    Maybe it’s something that is just learning how to grow that far north. Maybe it was there all along as mats and the changes in currents have pushed it into a place where it can be observed. Or maybe it was bound in/under/on ice and is free for the first time. However you cut it, strange goo circulating in the Arctic cannot be a good thing.

  43. 43
    glen says:

    Slightly OT.

    Gavin’s comment; “I personally don’t think that the intrinsic worth of a successful prediction of overall sea ice extent or area is that societally relevant – interest in open shipping lanes that might be commercially important need much more fine-grained information for instance – but I think the predictions are interesting for improving understanding of Arctic processes themselves (and hopefully that improved understanding will eventually feed into the models and provide better tests and targets for their simulations).”

    I read – Unexplained warming during the Palaeocene–Eocene Thermal Maximum – Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming.

    The paper could only explain 3.5C of the total estimated 5-9C temperature rise 55.5M years ago. This event is most interesting to me, because it has alot of smart people stumped. Maybe what is needed is a betting pool.

    With David J Beerling’s comment in mind I think this unexplained temperature rise is “societally relevant”.

  44. 44
    Steve L says:

    This is going to be an awful comment, due to my ignorance. First, the minimum seems kind of a fickle / twitchy / ephemeral thing to estimate. To me it seems more likely that better estimates could be made for a longer time period (eg mean September coverage) that would necessarily have more meaning. For Fraser River salmon, we don’t care if the temperature of some part of the river hits 21 C for an hour, but one week over 18 C means a lot of fish are going to die unspawned.

    Second, it seems to me that in terms of albedo, it’s the late spring / early summer coverage that’s important (when the sun is highest). So now I’m soapboxing the idea that the late summer extent isn’t what needs to be measured for climatological purposes. [I’m not a climatologist, meteorologist, physicist, etc, so I’m curious about how on or off that claim is.] Maybe the relatively low, Apr-Jul Arctic coverage in 2006 somehow stored more heat that resulted in the surprisingly low ice extent in late November that year, and maybe it also contributed to the 2007 record.

    Third, salinity affects the speed with which water freezes and presumably the rate at which ice melts. With the amount of ice melting and water freezing each year, it seems to be that there is likely to be an important effect of the mixing of the fresher surface waters with the saltier deep water. But nobody seems to mention that in these forecasting discussions. Am I out in left field here? Out in left galaxy?

  45. 45
    John Monro says:

    Apologies, I see the references to the Arctic Ice Forecasting Centre have been updated, in fact those are the forecasts that I’ve referred to later, it’s just that the links all refer to last year’s events. JKM

  46. 46

    #28 tamino

    I think this dandy little myth on global sea ice thing is generating from Monckton and Co.

    page 13 of his pdf

    They are mixing up the context of the signals as far as I can tell but I have not checked with NSIDC yet on this. Will update Moncktons page and include this silliness, after I have more time.

  47. 47
    MIke says:

    How much effect do the volcanoes at the ocean floor have an effect on the Arctic ice?

    [Response: None as far as anyone can tell. There was a good discussion of this on Dot Earth last year sometime. – gavin]

  48. 48

    #32 MJ Strong

    MJ you are looking at ice extent, but in what context?

    If you want to understand the problem with Arctic ice you need to understand the context of what is bad, vs. what is worse.

    Ice extent is only part of the picture. As Walt Meier (NSIDC) explained it’s like looking at the cover of a book from he top down. If you look top down, you cant tell how thick the book is.

    So looking at ice extent (surface ice cover) tells you nothing of the extent of the loss of sea ice mass, which is actually where the real story is.

    Take a look at a few of these images to get an idea of ice mass loss:

  49. 49
    Jacob Mack says:

    Slightly ot, but still relevant to this discussion: (2009)

    “I think it points out that the atmosphere is more complex than the computer models currently simulate,” says Dr. Roy Spencer, senior scientist for climate studies at the Global Hydrology and Climate Center (GHCC) at NASA’s Marshall Space Flight Center. “However, it does not by itself substantially alter the expectation that some amount of global warming will occur in the future.”

    “Spencer and Dr. John Christy, a professor of atmospheric science at the University of Alabama in Huntsville, are trying to account for the unexpected temperature patterns. By explaining the contrary behavior of atmospheric and surface-level temperature trends, they hope to improve computer models used to simulate the world’s climate. This would provide a better picture of how severe or mild global warming will be over the next century.”

    “I believe the data bolster the traditional scientific skepticism one must have when discussing predictions of the future,” Christy said. (back in 2000) (back in 1997)

    Now, I did see mention of problems with satellite data from several mods here, so I will not harp on that and being that new data and number crunching happens all the time, perhaps there has since been a validated proposal made to exaplain such disparities, however, a repeated and well researched answer to the aforementioned questions posed have yet to be provided by anyone in the relevant fields. Also I respect the work done in such sophisticated models, however, a lot of it just seems like esoterica.

    Of course nowadays “Global Warming,” is a household name and rightfully so; we as a human race should be concerned by the consequences of our actions, and especially our collective (global) ones.

    Fair NASA artical in PDF format. (long, but a rewarding read)

    The aspects of vector borne diseases are of great concerns and mid latitudes affected by warming may lose much plant and animal life that cannot adapt, but this “may,” is still speculation; ecological niches have shown enormous ability to adapt. Whether we are discussing prokaryotes which evolved long before we did,or us,human beings, survival has been facilitated through evolutionary processes. I do not mean to belittle the effects AGW “may,” bring about in the future, however, the models did overestimate water vapor feedbacks as they also underestimated ice sheet loss. The problems stem from both inadequate data from such a vast global climate system and lack of technology as of yet to simulate real world conditions in total. The physics is basically done as is the chemistry and of cousre by the mods admission no single or group of models can include all of the chemistry (especially) or dampings/forcings/feedbacks. In short we need a lot more research. The alternate energy sources need far more $ to have a true meaningful effect.

    Good summary:

  50. 50
    Jacob Mack says:

    I have seen your peer reviewed work gentlemen,but are there trend analyses of immense detail from several sources that strongly evidences model predictions are NOW far more accurate–show more appropriate water vapor feedback and sea ice loss? How are the correlations going in showing AGW= sea ice loss, in light of satellite issues?

    I am looking for large volumes of data and papers to look at to cross analyze and not just a paper or 2 from so and so and such and such. I have time again to do so, and I am eager for large databases and research sources.