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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. 601
    Matt says:

    Does anyone know why the World Glacier Monitoring Service only shows preliminary data through 2006-2007? Are they still in business?

  2. 602
    Hank Roberts says:

    Oh, and, dave p — your PgDn button is your friend:
    From http://nsidc.org/arcticseaicenews/

    —excerpt follows—–

    Conditions in context

    The average pace of ice loss during July 2009 was nearly identical to that of July 2007. Ice loss sped up during the third week of July, and slowed again during the last few days of the month.

    Averaged for the month, July 2009 saw a decline rate in ice extent of 106,000 square kilometers (41,000 square miles) per day. For comparison, the rate of decline for July 2007 was 107,000 square kilometers (41,000 square miles) per day and the July 2008 rate of decline was 94,000 square kilometers (36,000 square miles) per day. The Arctic Ocean lost a total of 3.19 million square kilometers (1.23 million square miles) of ice during July 2009, and dropped below ice extent at this time in 2008.

  3. 603
    Doug Bostrom says:

    Hank Roberts 7 August 2009 at 2:54 PM

    I believe manacker was citing “Climate Change 2007: The Physical Science Basis Summary for Policymakers”. It’s amusing to see him cling to this particular straw, loathsome as he no doubt regards the general bale of hay. But perhaps he’s had a change of heart.

    http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-spm.pdf

    wili 7 August 2009 at 2:40 PM

    There’s no “last word” here, or at least not until the moderators decide to terminate a thread. Formation Flyers such as manacker and BobFJhave endless canisters of chaff available to leave twinkling in the air, ready to dazzle our eyes. It’s impossible to vacuum it all up, but leaving the confusion unanswered is not only contrary to human nature but also risks a slide into further degeneracy.

  4. 604
    Rod B says:

    Wayne Davidson (591), Are you saying the Arctic ice melt proves the Hadley Center data is wrong? Or, what am I missing here? (I came in the middle of all…)

  5. 605
    Rod B says:

    wili (595), in a large pile of silly posts (IMO), you just won the gold medal.

  6. 606
    manacker says:

    Get with it, Hank (sigh!).

    You goofed again with your 596.

    Here is the link to IPCC SPM 2007. Check p.4.

    http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_SPM.pdf

    You will see that the RF for CO2 alone (1750-2005) is 1.66 W/m^2, while that for “total net anthropogenic” factors is 1.6 W/m^2, just as I said.

    Read and you will learn, Hank.

    Max

  7. 607
    dhogaza says:

    If you look at the arctic roos site, you’ll see their ice area measurement continues to steadily decline, though ice extent has leveled off. Since ice extent shows ice wherever density is > 15%, ice would seem to be a better indicator of melt (volume would be best of all).

    But … I don’t know how good that measurement by arctic roos is.

    What I do know is that a couple of months ago arctic roos was the denialist favorite ice site (since it showed ice extent lagging noticeably behind 2008, unlike nsidc or ijis. So make them eat that area graphic if they claim that melting has stopped! :)

  8. 608
    manacker says:

    Doug Bostrom (593)

    You ask: “Can we take from your reliance on IPCC data that you are in substantial agreement with the IPCC report for policymakers?”

    To answer your question:

    I believe that in its rather myopic fixation on anthropogenic factors, IPCC has identified the GHG impact of CO2 and other anthropogenic GHGs. IPCC has concluded that the equilibrium radiative forcing from all anthropogenic factors is roughly equal to that of CO2 alone (around 1.6 W/m^2), so that we can ignore the other factors for a rough estimate.

    IPCC has also informed us that “feedbacks from clouds remain the greatest source of uncertainty”, so we should look elsewhere for cloud impacts. Fortunately, there have been recent studies on this with empirical data (Spencer et al., Norris)

    In addition, IPCC has told us that its “level of scientific understanding” of solar impacts is “low”, so we should also look elsewhere for information on these impacts.

    There are, fortunately, several studies on the solar impact.

    The “positive feedback” assumptions of the GCMs cited by IPCC (leading to a 2xCO2 climate sensitivity of 3.2C) are also questionable, since they are based on model assumptions alone, and not on empirical observations, so I would be very skeptical of these.

    Does this answer your question?

    Max

  9. 609
    manacker says:

    Wayne Davidson (591)

    Wayne, I am not denying in any way that Arctic sea ice has shown a receding trend since 1979 when satellite measurements started, which appears to have started a reversal since 2007.

    What I am saying is that the average annual temperature at Illulisaat (Greenland), which you cited to Bob_FJ in reference to the Jakobshavn glacier , has not warmed over the entire 20th century, based on the temperature record there. There was a warming in the first half (1900-1950) and a cooling in the second half (1951-2005).

    So the glacial retreat at Illulisaat is not responding to late 20th century warming, but rather to something else.

    Got it?

    Maybe you have an idea what the cause of the Jakobshavn retreat has been.

    Max

  10. 610
    Hank Roberts says:

    This is why we ask for citations for the claims.
    And if you cited your sources the first time you post your claims, you wouldn’t end up repeating your ideas three or four or five times before you finally point to something people can look at to figure out what you’re talking about.

    Yep, that makes sense, if your purpose is to repeat your claims over and over.

    And now you’re claiming — with no source — that the IPCC doesn’t include published research that addresses the areas identified there as uncertainties, so you can claim it makes sense to look outside the IPCC’s reports for different science that’s more certain.

    Riiight.

    Omitting to mention the fact that the IPCC doesn’t do or publish research, it summarizes — the available science.

    Then you point — without citation — to names and make claims they have “empirical data” — as though other studies reviewed by the IPCC do not, or as though they have better data.

    Yes, there are newer studies since the cutoff for the last IPCC report.
    No, the ones you hint at without citation aren’t the only or best available science since the cutoff.

    Tedious.

  11. 611
    Hank Roberts says:

    Well, let’s see how Max / manacker is doing — try to cite.

    Max / manacker:

    > cloud impacts. Fortunately, there have been recent studies on this with
    > empirical data (Spencer et al., Norris) …
    > “positive feedback” assumptions … are also questionable, since they
    > are based on model assumptions alone, and not on empirical observations

    Perhaps “et al. and Norris” as pointed to recently by Spencer?

    http://www.sciencemag.org/cgi/content/abstract/325/5939/460

    Science, Vol. 325, No. 5939, 460-464 (24 July 2009); DOI: 10.1126/science.1171255
    Observational and Model Evidence for Positive Low-Level Cloud Feedback
    Amy C. Clement,1,* Robert Burgman,1 and Joel R. Norris2

    Hmmm. Positive feedback evidence, both model and empirical (observation).

    Nope, once again, Max /manacker — you make a claim, you vaguely asssert the research supports it, I look and find you’re misstating what’s out there./

    Well, it’s pointless trying to chase your claims, they just keep popping up.
    http://www.pbfcomics.com/archive_b/PBF216-Thwack_Ye_Mole.jpg

  12. 612
    dave p says:

    Re 602
    I realise melt in July was rapid but it is since then that the stall has occcured.

  13. 613
    BobFJ says:

    CTG you wrote in part 598:

    Max, it has been pointed out to you many times that it is wrong to say “It has not been warming since 1998 and has been cooling since 2001.”

    Perhaps CTG, you should read the earlier thread here entitled:
    Warming, interrupted: Much ado about natural variability— raypierre @ 12 July 2009
    https://www.realclimate.org/index.php/archives/2009/07/warminginterrupted-much-ado-about-natural-variability/#more-686

    There is no question that Ray Pierrehumbert (a highly respected professor of climate science here) agrees something along the lines of what Max says. In fact he refers to and discusses“a pause in warming“, and the debate is not about whether there is a pause, but what is causing it. Notice too, in the title: “Warming, interrupted”

    [Response: That was not written by Ray, it was written by Kyle Swanson. – gavin]

  14. 614
    Doug Bostrom says:

    manacker 7 August 2009 at 4:46 PM

    “Does this answer your question?”

    Well, not really, but that’s because I did a poor job with my question. Let me ask instead, do you agree with the portion of the report highlighted by the IPCC authors as of particular significance for policymakers and which you chose to cite in support of your position:

    ‘“The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6to +2.4] W m-2.”’

    Is there any part of that with which you disagree?

  15. 615

    #608 manacker

    Says:

    “myopic fixation on anthropogenic factors”

    Max, if you have no risk of losing your job or otherwise relevant reasons, please post your full name and stand by your words.

    Also, since you are so smart, please explain current warming without anthropogenic factors.

  16. 616
    Jacob Mack says:

    Hannk Roberts, # 61o, that is not accurate:”Omitting to mention the fact that the IPCC doesn’t do or publish research, it summarizes — the available science.” In fact the IPCC does their own research and publishes findings in their reports in addition to reviewing the latest research and evaluating it; this is a minor distinction as mainly they do on fact review the literature. Still if you read 2008’s Climate change and Water and the AR4, you will see IPCC lead research and individually publsished research from its members for the actual reports. Maybe you meant on the whole and as a whole the IPCC does not does not do or publish research? A minor distinction, but still an important one. Your other points are still accurate.

  17. 617
    Doug Bostrom says:

    manacker 7 August 2009 at 5:01 PM

    “Wayne, I am not denying in any way that Arctic sea ice has shown a receding trend since 1979 when satellite measurements started, which appears to have started a reversal since 2007.”

    Really. Has it? How do you come to that conclusion? We have one complete year of data since 2007, one partially complete set of observations. They don’t look particularly hopeful but even if 2008 had been a stellar year compared with 2007, which it was not, one would be naive to draw any conclusions. Look at the record to see the folly in working from a single year’s data.

  18. 618
    manacker says:

    Sorry, Hank (611)

    Your claims are wrong again (sigh!).

    IPCC has stated that “cloud feedbacks remain the largest source of uncertainty”. Earlier studies (Ramanathan and Inamdar) stated that the overall impact of clouds was one of strong cooling (“several times the 4W/m^2 heating expected from a doubling of CO2”) and that “the magnitude as well as the sign of the cloud feedback is uncertain”.

    Spencer et al. helped to clear up this “largest source of uncertainty” with empirical observations showing a strongly negative net feedback from clouds with warming (I’m sure you have seen this study).

    This would indicate that the overall 2xCO2 climate sensitivity is around 0.6 to 0.8°C (rather than 3.2°C, as assumed by all the GCMs cited by IPCC).

    Max

    [Response: Spencer has shown no such thing despite his claim to have done so. All models do not assume that sensitivity is 3.2ºC. And yes, there are empirical studies suggesting just as large values (and sometimes larger). Since this is the umpteenth time you have said this and the umpteenth time you have been corrected, perhaps a small time out is appropriate so that something else can be talked about. The internet may be unbounded, but my threshold for unending repetition of error is not. – gavin]

  19. 619

    manacker wrote in 608:

    IPCC has also informed us that “feedbacks from clouds remain the greatest source of uncertainty”, so we should look elsewhere for cloud impacts. Fortunately, there have been recent studies on this with empirical data (Spencer et al., Norris)

    I see what you mean:

    Is this feedback present in climate models? To address this question, we analyze the 20th century climate simulation in 18 coupled ocean-atmosphere general circulation models with comprehensive output available from the World Climate Research Programme’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel archive (38, 39)….

    By eliminating models successively on this basis, we are left with only two that simulate the correct sign correlations for all variables, the INMCM3.0 and the HadGEM1. Because these two models represent opposite ends of the range of values of equilibrium climate sensitivity (INMCM3.0 has the lowest value and HadGEM1 has the highest) (5), the cloud-meteorology correlation test alone is not a sufficient metric for global climate sensitivity….

    The analysis presented here provides observational evidence that this feedback is positive in the NE Pacific on decadal time scales. The only model in the CMIP3 archive that properly simulates clouds in the NE Pacific and exhibits 2 × CO2 circulation changes that are consistent with multimodel mean produces a reduction in cloud throughout much of the Pacific in response to greenhouse gas forcing (i.e., a positive feedback).

    Observational and Model
    Evidence for Positive Low-Level
    Cloud Feedback
    Amy C. Clement, Robert Burgman, Joel R. Norris
    Science, Vol 325, pp 460-4
    24 July 2009 Vol 325

    In all fairness, though, the next sentence is, “Evaluating cloud feedback with one model is, however, far from ideal.”
    *
    manacker wrote in 608:

    The “positive feedback” assumptions of the GCMs cited by IPCC (leading to a 2xCO2 climate sensitivity of 3.2C) are also questionable, since they are based on model assumptions alone, and not on empirical observations, so I would be very skeptical of these.

    The climate models make no “positive feedback” assumptions. They are based upon the principles of physics and both negative and positive feedback are the result. But predominantly the feedback is positive. And last I checked, the principles of physics (as they describe radiation transfer, fluid flow, thermodynamics, gravity and so on) were empirical in nature.

  20. 620
    manacker says:

    Doug Bostrom (614)

    Yes, I would agree that IPCC has probably done a fairly good job on estimating the theoretical GH impact of CO2 plus all other anthropogenic factors (i.e. the IPCC “specialty”).

    If IPCC puts this radiative forcing at 1.6 W/m^2 since 1750 I can buy that. It tells me that all other anthropogenis factors besides CO2 essentially cancel one another out. It also relates to a 2xCO2 climate sensitivity of sightly below 1 degree C, with which I could also agree.

    Does this answer your question?

    Max

  21. 621
    BobFJ says:

    Gavin, Reur comment on my 613:

    [Response: That was not written by Ray, it was written by Kyle Swanson. – gavin]

    But the fact that the title of the article is endorsed thus: — raypierre @ 12 July 2009, and his responses to comments include the same terminology surely means that he seconds the author?

    [Response: You’d have to ask him. All the post authorship means is that he prepared the posting. It’s safe to assume that he saw some merit in it being posted, but assuming complete agreement without a specific statement is not warranted. – gavin]

  22. 622
    Hank Roberts says:

    Jacob, please check your source.

    This is mine: http://www.ipcc.ch/organization/organization.htm

    “The IPCC is a scientific body. It reviews and assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change. It does not conduct any research nor does it monitor climate related data or parameters.”

  23. 623
    manacker says:

    Doug Bostrom (617)

    Please read posts a bit more carefully.

    I wrote that the net receding trend of Arctic sea ice “appears to have started a reversal since 2007”.

    Got it?

    I did not say that this reversal was a new trend.

    Maybe it will become a new trend (I personally doubt it, but who knows?).

    Max

  24. 624
    Hank Roberts says:

    Max / manacker claims “a reversal” — but

    “… The average pace of ice loss during July 2009 was nearly identical to that of July 2007. Ice loss sped up during the third week of July, and slowed again during the last few days of the month….”

    From http://nsidc.org/arcticseaicenews/ — use PgDn to find it on the page.

  25. 625
  26. 626
    manacker says:

    Gavin

    You are right in your comment to Bob_FJ that the lead article was not written by Ray Pierrehumbert, but:

    On the RC blog cited by Bob_FJ Ray Pierrehumbert wrote:

    “ I think the connection is very intimate. We at RC think that some of the Keenlyside results “predicting” an interruption of warming were overstated and misinterpreted, but for me personally the take-away message from Keenlyside is that ocean dynamics is capable of producing a temporary warming interruption, even in the face of growing radiative forcing,”

    “It’s too soon to say whether the current “pause” in warming is anything more than statistics being clouded by one unusual El Nino event, but we should be thinking now about possible explanations just in case something more interesting is going on”

    So he definitely recognizes a ‘current “pause” in warming’ but believes that there could be possible explanations for this pause, which should be investigated.

    Just to clear this point up.

    Max.

  27. 627
    BobFJ says:

    Wayne Davidson 591, you wrote in part to Max:

    2001 when your claim it has been cooling ever since; Really?? Sea ice utterly denies your reasoning….

    You could perhaps check 543/p11 for moreinfo, but sea ice is not only affected by air temperature but also wind, currents and water temperature plus a few lesser things.

  28. 628
    Doug Bostrom says:

    manacker 7 August 2009 at 5:46 PM

    “Yes, I would agree that IPCC has probably done a fairly good job on estimating the theoretical GH impact of CO2 plus all other anthropogenic factors (i.e. the IPCC “specialty”)…

    Does this answer your question?”

    Yes, to a fault, which I removed.

    manacker 7 August 2009 at 6:08 PM

    “Please read posts a bit more carefully.

    I wrote that the net receding trend of Arctic sea ice “appears to have started a reversal since 2007″.

    Got it?

    I did not say that this reversal was a new trend.”

    Yeah, I get that when you make a careless mistake you’re pretty good at splitting hairs so as to save face. So “reversal” does not imply direction? In that case why did you not say “dither”?

    I think it’s late in Switzerland and you should go to bed.

  29. 629
    manacker says:

    John Reisman

    You wrote (619): “Try not to get to hung up on the weather and ice extent changes in the short term” and then referred me to studies on Arctic sea ice.

    The loss of Arctic sea ice since 1979 is well-documented.

    The growth of Antarctic sea ice is also well-documented (but less frequently referred to by NSIDC and others).

    The unrelated story of the Jakobshavn glacier was discussed previously, and I checked the long-term local temperature record there since 1900. (This is primarily grounded ice and not floating sea ice.) A NASA report tells us: “The ice stream’s speed-up and near-doubling of ice flow from land into the ocean has increased the rate of sea level rise by about .06 millimeters (about .002 inches) per year, or roughly 4 percent of the 20th century rate of sea level increase. “
    http://www.nasa.gov/vision/earth/lookingatearth/jakobshavn.html

    I found that there was a strong local warming in the first half of the 20th century and a cooling since 1951, with an overall slight cooling over the entire period 1900-2005. This surprised me, since it pointed out that the glacial retreat there was not related to local late 20th century warming (as many would assume), but to something else.

    Maybe someone on this thread has an answer to this quandary.

    Max

  30. 630
    manacker says:

    Hank Roberts (624)

    You are right.

    Arctic sea ice extent in July 2009 was around 1.3 million km^2 below the 1979-2000 baseline and 0.68 million km^2 above the July 2007 low.

    So we have only “recovered” about one-half of the long-term loss.

    Who knows what will happen next year (July 2010)?

    Not me. Not you. Not Mark Serreze of NSIDC.

    Max

  31. 631
    Jacob Mack says:

    Hank,
    here is my source: http://www.ipcc.ch/

  32. 632
    Jacob Mack says:

    Hank,
    may be exhaustion on my part; I could have sworn I read somewhere on the site I pasted that there was actual research conducted by IPCC or many IPCC individuals on the 2008 Climate Change and Water; after a nap, I will do a more thorough search, if I still do not find it, I will recant my statement.

  33. 633
    Hank Roberts says:

    OK, Jacob.

    Now –from that page, that you point to as your source for what you believe:

    click “Organization” — first tab in their left sidebar on that page.

    Look at the second paragraph.

    There is no research done by the IPCC.
    They don’t publish any research.
    They review published research, from the science in the journals.

  34. 634
    Hank Roberts says:

    OK, naps are good; our postings overlapped and I just saw yours.

    This is important because folks spin the facts.

  35. 635
    Hank Roberts says:

    Max / manacker trots out the old confusion talking point, about Antarctic sea ice, as though it proved his idea instead of disproving it.

    Ask an ice guy. That question, in fact, was recently asked here:
    http://moregrumbinescience.blogspot.com/2009/08/question-place.html

    And answered:

    “Blogger Penguindreams said…

    Eric: You raise a point I’ve been meaning to give a full post to. Namely, increased Antarctic ice area is expected from a greenhouse warming. This goes back to Manabe in the early 1990s. The mechanism he saw in his model was that in the warmed climate, there was more snowfall onto the ice pack. The snow gets converted to ice (if there’s enough of it to sink the top of the floe below the sea level), or simply acts as an insulator for the ice. The rising trend in Antarctic ice was not statistically significant until much later. But then we (Markus and Cavalieri) also observed that there was more snow on the Antarctic ice pack.

    So, a very successful prediction out of the climate model.”

    ——
    Funny how people don’t remember this and post to the contrary over and over.

  36. 636

    #630 manacker

    Again wit the short term v. long. What is it prevents you from understanding the difference between short term weather and long term climate trends.

    Looks like cherry jubilee in here these days.

    #631 Jacob Mack

    Can you be a little more specific please.

  37. 637
    CTG says:

    Re 613. BobFJ, the Kamikaze Denial Troll strikes again. Are you paid by the word for the garbage you churn out?

    Max said “it has been cooling since 2001”. This is wrong. You know it is wrong. Max knows it is wrong. And yet you both continue to say it, knowing it to be wrong.

    Why should we listen to a word you two say?

  38. 638
    tamino says:

    Re: #609 (manacker)

    You seriously mischaracterize the temperature history in Ilulissat by saying “warming in the first half (1900-1950) and a cooling in the second half (1951-2005).” Although there was cooling for much of the time span from 1951 to 2005, there was very strong warming for more than the last decade. Linear regression of CRU data for Ilulissat from 1992 to the end of 2005 (the end of the CRU data) gives a warming rate of 37 +/- 15 deg.C/century.

    According to this report on Jakobshavn,

    The data showed that the glacier slowed down from a velocity of 6700 meters (4.16 miles) per year in 1985 to 5700 meters (3.54 miles) per year in 1992. This latter speed remained somewhat constant until 1997. By 2000, the glacier had sped up to 9400 meters (5.84 miles) per year, topping out with the last measurement in spring 2003 at 12,600 meters (7.83 miles) per year.

    Re: #630 (manacker)

    I’ll leave it to others to correct your arithmetic.

  39. 639

    #609… Max:

    “Illulisaat (Greenland), which you cited to Bob_FJ in reference to the Jakobshavn glacier , has not warmed over the entire 20th century, based on the temperature record there. There was a warming in the first half (1900-1950) and a cooling in the second half (1951-2005).”

    Sorry I am unfamiliar with this argument since I have not replied to Bob yet…

    ….. “which appears to have started a reversal since 2007.”

    absolute nonsense, in terms of ice thickness, and especially weather related events leading to the melts.
    Sea ice is a true metric of Global temperatures, There is a close relation between GT’s and Arctic sea ice extent or volume at minima. 2007 being the warmest year in history for the northern hemisphere , 2007 the greatest minima in history. A cold winter GT wise gives the same effect, more ice extent.

    Now I have discovered a relation between ENSO and clouds, which affect sea ice, as per this year, cloudier than usual Canadian Arctic can be seen as a sea amongst sea ice “footprint” . 2007 during solstice had unprecedented clear skies during La-Nina leaning conditions which have left a sea print amongst open water quite unlike 2009 with reverse ENSO effects. Claiming that the ice melt as stabilized is incorrect.

    Bob:

    “You could perhaps check 543/p11 for moreinfo, but sea ice is not only affected by air temperature but also wind, currents and water temperature plus a few lesser things.”

    My oh my, novice arguments don’t impress. Winds would leave a definite sea ice pattern easily recognizable, but winds against a well frozen pack, laced with multi year ice has never rid the Arctic ocean as now a days (in the past winds were just if not more ferocious)… Wind is a significant player amongst much thinned and scattered ice due to melting.

    Sea currents are rarely if ever different, a near constant, except for velocity, same reasoning for winds applies.

    Recent Warmer Water temperatures…. Last I looked … Are and can be caused by AGW!!!!!

  40. 640
    Jacob Mack says:

    Hank,
    I stand corrected.

  41. 641
    Steve Fish says:

    Gavin’s response to #618. I emphatically support your comment. The decrease in signal to noise in this thread is greatly hampering my climate science education and is very irritating.

    Steve

  42. 642
    Hank Roberts says:

    > Jacobshaven

    Remember it’s not the average temp; it’s the melt ponds on the surface at the warm part of the year that change the ice, even if the average for the year is cooler

    Note that glacier has another name, and searching on both may be helpful.

    That is discussed in the Q&A quite a bit, you could pick up that thread about here:

    https://www.realclimate.org/index.php/archives/2005/10/q-a-global-warming/comment-page-1/#comment-5042

    Look for the inline replies from the Contributors there, and the pointers, but remember — check for more recent papers citing these; follow the science forward in time, no one paper is _the_ answer you’re looking for:

    http://www.nature.com/nature/journal/v428/n6979/full/428114a.html
    http://www.sciencemag.org/cgi/content/abstract/1115356v1
    http://www.sciencemag.org/cgi/content/abstract/310/5747/456

  43. 643
    Hank Roberts says:

    Jacob — no worries, the secret behind my habit of trying to always give a good cite is, I don’t trust my memory.

    I can’t rely on it even to be accurate as of the last time somewhere in the past when I caught up on a subject, let alone up to date.

    It’s a poor sort of memory that only works backward.
    Lewis Carroll
    English author & recreational mathematician (1832 – 1898)

  44. 644
  45. 645
    Jacob Mack says:

    Yeah Hank, of course you are right…I have been burning the candle at both ends lately and I read many reports through and through these last few days, so I am better off in the future going back to the specific citation first.

  46. 646

    In a certain very sad sense, wili (595) is correct.

    Here we are at 644, and manacker repeats his nonsense, and gavin’s patience is infinite and to what effect?

    More of the same repetitive nonsense that most of us have seen for months if not years.

    Is this useful? How?

    I think Hansen has it right.

  47. 647
    Hank Roberts says:

    > Is this useful? How?

    When some guy is posting bad information, make sure the guy’s name or pseudonym is posted along with the refutation, each time, and point to good information that people can read for themselves to see that he’s wrong.

    Answer them all, and let Google sort them out.

  48. 648

    manacker writes:

    It has not been warming since 1998 and has been cooling since 2001.

    IPCC (and Hadley) have “failed predicting anything about present cooling conditions” (or “interrupted warming conditions”, as some prefer to call it).

    It’s not cooling:

    http://BartonPaulLevenson.com/VV.html

    http://BartonPaulLevenson.com/Ball.html

    http://BartonPaulLevenson.com/Reber.html

  49. 649

    Looking at manacker’s posts from 587-606, I’m guessing he doesn’t understand what “net” means. manacker, if there has been a “net” warming of 1.6 W/m^2, and there has been cooling of 1.6 W/m^2, it means the gross warming must have been 3.2 W/m^2. “Net” means the balance after the positives and the negatives have been added together.

  50. 650

    manacker writes:

    IPCC has also informed us that “feedbacks from clouds remain the greatest source of uncertainty”, so we should look elsewhere for cloud impacts. Fortunately, there have been recent studies on this with empirical data (Spencer et al., Norris)

    And the most recent study concludes that cloud forcing is positive; i.e., will make warming worse:

    Clement, A.C., Burgman R., and J.R. Norris 2009. “Observational and Model Evidence for Positive Low-Level Cloud Feedback.” Science 325, 460-464.

    In addition, IPCC has told us that its “level of scientific understanding” of solar impacts is “low”, so we should also look elsewhere for information on these impacts.

    There are, fortunately, several studies on the solar impact.

    Here’s a very simple one:

    http://BartonPaulLevenson.com/Sun.html

    The “positive feedback” assumptions of the GCMs cited by IPCC (leading to a 2xCO2 climate sensitivity of 3.2C) are also questionable, since they are based on model assumptions alone, and not on empirical observations, so I would be very skeptical of these.

    Nobody’s ever observed that there’s more water vapor pressure when it’s hotter? Or that melting bright ice leaves dark land under it?