Go Ice Go! … Going … Going … Gone!!!

When it comes to up-to-date measures of arctic sea ice, the most popular choice with Anthony Watts and Steve Goddard is the estimated extent from DMI. Others seem to prefer NSIDC data for monthly averages of both sea ice area and sea ice extent, or JAXA for daily data on sea ice extent, or daily sea ice area data from Cryosphere Today. So there are several satellite-based data sets to choose from, but Watts seems to prefer, and Goddard seems to love, the DMI data.

Wonder why?


It’s for two reasons:

  • First: they’re daily data so there’s more opportunity to focus on momentary statistical noise, in order to divert attention away from the trend in the physical signal.
  • Second: DMI data don’t start until 2005 — they cover less than 6 years.
  • Case in point: just a few days ago Watts posted about what he clearly implies is a “recovery” of arctic sea ice. He even titled his post “Go Ice Go!” His reason for cheering arctic sea ice? This:

    He even gives us a closeup view of the summer season:

    To consider arctic sea ice to be in “recovery” you have to do two things:

  • First: pick just the right moment, when statistical noise makes some day’s daily value higher than the same day for the preceding five years.
  • Second: use the DMI data so you only have to compare to the preceding five years.
  • Watts also shows the data from JAXA:

    Now there’s more data — there’s a little more than 8 years. This time, however, Watts omits the close-up. Why? Maybe because it looks like this:

    I have a question for Anthony Watts:

    We have over 30 years of satellite data for arctic sea ice. Why do you consistently display the only data source I know of that covers less than 6 years?

    Maybe some of you would enjoy visiting WUWT to put the question directly to Anthony. Think he’ll answer? Think he’ll even allow the question?

    I like daily data myself, because it has more information than monthly averages. But I’m fully aware that the extra information is almost all about the day-to-day noise, almost nothing about the trend. So I’m content to use monthly averages to investigate what the physical signal is.

    But it’s easy to get daily data covering over 30 years from Cryosphere Today. These data are for arctic sea ice area rather than extent, but face it, both will indicate what the trend is. Here’s what you get doing a similar comparison using over 30 years of data (this year in red):

    Here’s the close-up:

    Does that look like a recovery to you?

    Let’s look at the actual trend in summertime arctic sea ice. Here’s NSIDC data for the September monthly average over the last three decades. I’ve superimposed a rapidly declining trend, my 2010 prediction based on that trend (red dot with error bars), and what actually happened (black “x”):

    Does that look like a recovery to you?

    I have two predictions:

    First: Now that NSIDC data for this September are available, I’ll do as I did before: fit a quadratic trend to the September average data from NSIDC, then use that trend to predict that next year’s September average from NSIDC, and next year’s JAXA minimum, will be 4.63 +/- 0.9 million km^2. After all, the best predictor of future behavior is past behavior: the trend continues.

    Second: Either Anthony Watts won’t answer my question about why he’s so fond of less than 6 years’ data when we have over 30 (and that’s just from satellites) — or he’ll attack me personally, calling me a coward for blogging under a pseudonym. After all, the best predictor of future behavior is past behavior.

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    52 responses to “Go Ice Go! … Going … Going … Gone!!!

    1. Sadly, that adage–”the best predictor of future behavior is past behavior”–seems to apply to most North American Federal-level efforts to mitigate emissions, too. But I haven’t given up hope that that may change before the Arctic actually goes ice-free for the first time.

      And both will occur before any meaningful change from Sire Watts.

    2. “After all, the best predictor of future behavior is past behavior: the trend continues”

      Er. That’s only true when you have a physics based reason to believe in a continuing trend (in this case, greenhouse gas induced warming). I object to the statement in general, because I see the skeptics use it all the time to downplay continuing trends as being natural, when in many cases, the best predictor of future behavior in climate (absent external forcing) is actually regression to the long-term mean.

      I suppose it requires having a good physical intuition of the appropriate time period to use in defining the trend… (for what its worth, I do agree with your projection for Arctic sea ice).

      -M

    3. I recently wasted too much of my free time trying to correct some misconceptions over there. My conclusion is that no one over there wants to hear it. And if the mods don’t like you they will use any technicality in the guidelines (which are already stacked against anyone that disagrees) to intimidate you.

      BTW, you will know when the really don’t like you when Anthony sends Ashley phishing for your phone number.

    4. I certainly hope that now that Anthony has published a full response to your question, you will publish it here.

      [Response: I'll reply.]

    5. It is hard to be impressed with you claiming that 30 years Arctic ice records is better than 5 years [edit]

      [Response: It's hard to be impressed with you for implying that it's not.]

    6. Anthony replied to your question.

      What data source is he missing? He shows JAXA, NANSEN, University of Bremen, NSIDC, Canadian Ice Service, Univeristy of Ilinois, NOAA ESRL temps and he covers both hemispheres.

      [Response: Only on his sea ice page. In his posts, he diligently avoids data pre-2002 -- because it makes his claims of "recovery" look like what they are: foolish.]

      • Umm, have you looked at the original data sources?

        [Response: Yes.]

        The graphs in the original sources use the data Mr. Watts links to – he doesn’t create the graphs himself.

        [Response: But he consistently choose for display, graphs which show an extremely limited amount of data. The original sources do so for good reason, and just as prominently feature enough data in graphs to provide proper context. Watts does so for bad reason, namely to avoid proper context because it contradicts his misinformation campaign.]

        Please see the links at the bottom of Watts Sea Ice PAge to go to the original sources.

    7. Just The Facts

      Tamino

      Who are you kidding? The Warmists fear the facts, whereas Skeptics embrace them. Here is a post I made on WUWT in June:
      http://wattsupwiththat.com/2010/06/23/sea-ice-news-10/#comment-415693

      Note how we Skeptics direct the curious minded to the data sources so they can make up their own minds? If you are so openminded then post links to the sea ice data sources;

      [edit]

      [Response: Note that every data source mentioned in this post includes a link to the data.]

    8. Anthony Watts allows posters to put up anything they want at WUWT, excepting ad hominem attacks or seriously off-topic remarks.

      I can’t imagine why anyone would say differently.

      [Response: Because in the past, he has deleted comment ex post facto (after approving them) when things got too hot for him]

      • Human-

        Read Anthony’s posting guidelines. He is very clear that he will not respect your privacy. He also makes no claims as to enforcing his rules evenly. If a poster uses the “denier” in most any context other than “in quotes” it is “gloves off” for his mods, yet posters can use whatever terms they wish (and do) for then general populace they disagree with.

        Human…Review Anthony’s replies to recent posters he disagrees with (one example: “…Such rubbish I’ve never seen. These guys are clueless. So are you.” (Peer Reviewed thread) Frankly, I have no problem with such a response, but I assure you that if I had made that comment at WUWT it would never have made past the mods, they would have snipped my whole comment.

        I’ll tell you something else Human: I have been using “arch stanton” at multiple websites on the web for a couple years now. My email adress associated with that handle has never been spammed. I used it last at WUWT months ago, but I have thought better of it since, so more recently I have been using Yuba Yollabolly there. I have not bothered to disguise my IP (it would be easy enough to do with a proxy server). On the day after a mod falsly acusses me of posting in the same thread under different names arch stanton’s email adress gets it’s first spam ever from one “Ashley Williams” looking for my phone number. I have read about others claiming things like this about WUWT but I did not believe it until now.

      • thefordprefect

        Say the wrong thing on Watts’ site and he goes to the trouble of checking your ip address then suggests that you are posting on employers time (there is even hints that these may be contacted), are posting from a university and so should have faith in your musings.
        If you are really against his views then an outright ban ensues.
        http://climateandstuff.blogspot.com/search/label/censorship

    9. Tamino, look to WUWT. you question is there.

    10. Given that we only have 30 years of scientific data, it seems unlikely we can draw any conclusions about where sea ice extents may be going. There is written evidence that suggests, during the 1930′s and 40′s, Arctic sea ice may have been the same as, or lower then, the currently measured extent.

      [edit]

      [Response: We have a lot more than 30 years of data, but we only have a little more than 30 years of satellite data. The data we have (some of which predates 1900) contradicts you.]

    11. Guess WUWT?? (Pun intended):

      http://wattsupwiththat.com/2010/10/15/my-answer-to-taminos-question/

      By the way, it’d be nice if you would include some discussion about Antarctic Ice along with Arctic Ice. Could be and interesting discussion.

      [Response: I will.]

    12. Your question answered !!

      http://wattsupwiththat.com/2010/10/15/my-answer-to-taminos-question/#more-26478

      [Response: Wrong. Watts replied -- but he didn't answer.]

    13. Looks like Anthony has posted a response.
      http://wattsupwiththat.com/2010/10/15/my-answer-to-taminos-question/#more-26478

      [Response: Too bad his response doesn't answer the question. He just lies about it.]

    14. Before complaining too much maybe you could check this link.
      http://wattsupwiththat.com/2010/10/15/my-answer-to-taminos-question/#more-26478

    15. “After all, the best predictor of future behavior is past behavior: the trend continues.”

      Not necessarily. It’s called a variable.
      If you Start at Point A and drive to point B, it takes you X amount of minutes.
      The next day you start at A, drive the same way, leave the same time, and yet it takes you Y minutes.
      Why?
      Because you forgot your briefcase and had to go back. Maybe there was a car accident. Maybe it was raining so you drove slower. There were a thousand possible outcomes that you couldn’t predict.
      And that, is what you’ve done with your graphs.
      For a simpler explanation, if you require one, watch ” Jurassic Park.” There is a excellent presentation by the mathematician involving a drop of water and a steady hand.
      Plus, it has dinosaurs. You and your friends will be impressed.

    16. Oh for Pete’s sake. Here’s your challenge.

      We have over 30 years of satellite data for arctic sea ice. Why do you consistently display the only data source I know of that covers less than 6 years?

      If you are so are so much into semantics, I must point out that you said “display” not “post”…

      Geesh!

      [Response: You're the one who's playing semantic games. The emphasis of Watts' posts is glaringly obvious.]

      • If you want to play semantics, note that Tamino said “display the only”, not “only display”. Tamino, like scientists in general, is careful with words.

        Try it sometime.

    17. Just The Facts

      For those of you who would like to do some of your own digging here are some of the best sea ice data sources:

      The Cryosphere Today – Arctic Climate Research at the University of Illinois:
      http://arctic.atmos.uiuc.edu/
      http://arctic.atmos.uiuc.edu/cryosphere/
      http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/

      National Snow and Ice Data Center (NSIDC):
      http://nsidc.org/
      http://nsidc.org/data/seaice_index/images/
      http://nsidc.org/searchlight/

      University of Bremenpart
      http://www.iup.uni-bremen.de/eng/
      http://www.iup.uni-bremen.de/iuppage/psa/2001/amsrop.html
      http://www.iup.uni-bremen.de:8084/

      International Arctic Research Center/Japan Aerospace Exploration Agency (IARC-JAXA)
      http://www.ijis.iarc.uaf.edu/en/
      http://www.ijis.iarc.uaf.edu/en/home/

      Danish Meteorological Institute (DMI)
      http://ocean.dmi.dk/english/index.php
      http://ocean.dmi.dk/arctic/index.uk.php

    18. “Maybe some of you would enjoy visiting WUWT to put the question directly to Anthony. Think he’ll answer? Think he’ll even allow the question?”

      OK. Let’s assume that the statement “Watts replied — but he didn’t answer.” is a statement of fact and not semantics. Are you at least prepared to admit that you were wrong in speculating Watts wouldn’t allow the question?

    19. Reading the comments here and the commentary makes me wonder why some here are so anti the skeptical enquiring mind. It is a pre-requisite for all true scientific endeavour. Belief without proof is faith.
      I do hope you all enjoy the coming Northern Hemisphere ski season, it will be a doozy.

      [Response: Stupidity is not skepticism.]

    20. Just The Facts

      This 31 year Global Sea Ice Area chart is interesting:
      http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg

      • And exactly what do you think it shows?

        A decrease. Duh.

        Even the Antarctic increase isn’t enough to compensate for the rapid Arctic decline. And the fact that the poles are – well, at opposite poles, means the seasons are out of phase, so there will always be a large absolute amount of ice globally, until eventually winter ice extent is significantly reduced, too.

        This isn’t hard. Why are you so baffled by it?

        • Just The Facts

          I concur that there appears to be a decline in average Global Sea Ice Area, all be it slight. “Baffled”? I said the chart was “interesting”.

          “Even the Antarctic increase isn’t enough to compensate for the rapid Arctic decline. ”

          It seems that we can agree that Antarctic Sea Ice is trending higher:

          Here’s Antarctic Sea Ice Extent from NSIDC;
          http://nsidc.org/data/seaice_index/images/daily_images/S_stddev_timeseries.png

          Here’s another view of Antarctic Sea Ice Extent from Bremen;
          http://www.iup.uni-bremen.de:8084/amsr/ice_ext_s.png

          Here’s the monthly trend in Antarctic Sea Extent from NSIDC;
          http://nsidc.org/data/seaice_index/images/s_plot_hires.png

          Here’s Southern Hemisphere Sea Ice Anomaly from Cryosphere Today:
          http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.antarctic.png

          What I find “interesting” about the Global and Antarctic Sea Ice charts is that I don’t see signs of rapid and catastrophic warming, do you?

        • What I find “interesting” about the Global and Antarctic Sea Ice charts is that I don’t see signs of rapid and catastrophic warming, do you?

          Hold on a second – you were just claiming that you weren’t baffled. Yet here you go, saying spectacularly dumb things like this. Why are you so flummoxed by the sight of increasing sea ice in Antarctica? So much so, that it leads you to deny that warming is happening, and to turn a blind eye to the Arctic, which is where we expect to see most warming.

          After you spammed us with all that Antarctic data, trying to make a point that nobody is denying, you really don’t have much credibility left. Why are you working so hard to fool yourself into thinking that the evil warmists are hiding the Antarctic data?

          The only reason we don’t talk about it more is because the mechanisms are complicated, and usually deniers’ heads explode. We don’t want to clean up the mess.

          Prove us all wrong. Go and learn about Antarctic ice, and come back to show off your new-found knowledge and un-exploded head.

    21. Watts does indeed seem rather selective in his choice of shorter-term data for sea ice stories on his site. His rebuttal points rather to his reference page on sea ice that has a wide variety of data series, including long-term trends.

      As you say, the long-term trend is more important, and your quadratic does indeed seem to fit the 30-year record very closely. The trend may change of course but what is the formula for the trend line now that 2010 data are included, and in what year would sea ice reach zero if the present formula held? It looks like about 2025 from the graph.

      • Past behaviour as a predictor for future behaviour is a really excellent method for short term prediction. It even works well for something as chaotic as weather. However, it’s useless in the longer term, as Tamino knows. And that’s why he hasn’t made any “ice-free” predictions.

        The people working with full ice models may feel more confident about making such predictions – but they are hedged with such huge uncertainties that they don’t help except to say “sooner rather than later”.

    22. While an egocentric liar like Watts makes a highly amusing target, I don’t imagine that pointing out his lies and other inadequacies is actually going to change anything or educate anyone. And the downside, of course, is the massive influx of clueless yes-men, all defending their hero…. and displaying quite mind-boggling reasoning skills.

      • Quite correct Didactylos, but just imagine how bad it would be if we were to let them to run amok?

        And just to validate your prediction, enter “Brad” @October 16, 2010 at 11:06 am :0)

    23. …and most of his graphs show the post-1979 average. How is that lying?

      [Response: Bull. Some do, but in Watts' case I wouldn't say "most." And his love affair with DMI and JAXA is precisely because they don't even have data prior to 2005 and 2002.]

    24. Just The Facts
      Here is another site that has a lot of interesting information, and does some comparisons of the different sources.

      http://www.climate4you.com/

      P.S. Seems you hit a raw nerve on your “friend” Didactylos. Excitable chap he is.

      • J. Bob – that sounds most unwise. Why get your data filtered through a highly biased website, when you can go to the source, and find out what the scientists responsible for the data have to say about it?

        I am always wary of sites that present large quantities of unrepresentative data.

      • P.S. Seems you hit a raw nerve on your “friend” Didactylos. Excitable chap he is.

        Pshaw.

        Pointing out that a denier is being “spectacularly dumb” is just housekeeping.

    25. Just The Facts

      I am not going to bother addressing Didactylos, as I have better things to do with my time than fend off empty Ad Hominems. The point of posting the Antarctic Sea Ice links was simply to see if there were any limits on posting data sources on Open Mind, and I give Tamino credit for posting them.

      In terms of my statement above, that “What I find “interesting” about the Global and Antarctic Sea Ice charts is that I don’t see signs of rapid and catastrophic warming, do you?” I would welcome a reasoned critique/challenge to its validity. In fact, I would welcome a calm and reasoned debate with anyone who is open to it.

      [Response: Let's begin by asking your opinion of the northern hemisphere data.

      Look at the graph of summer minimum based on combining HADISST and satellite data from NSIDC (the red curve in the 2nd graph in this post). Do you "see signs of rapid and catastrophic warming" there? If not, how rapid, and how extreme, would the decline have to be, to meet that criterion?]

      • Just The Facts

        Looking at this NSIDC Northern Hemisphere Monthly Extent Anomaly chart;
        http://nsidc.org/data/seaice_index/images/n_plot_hires.png

        I think there is no doubt that there has been a significant and rapid decrease in Arctic Sea Ice Extent during the last 30 years, especially in 2007. In terms of how much of this decrease was the result of warming, versus other factors such as wind;
        http://www.sciencedaily.com/releases/2010/04/100427111449.htm

        I am not sure, but I would certainly concede that warming has had a significant impact.

        In terms of whether the decrease in Arctic Sea Ice is catastrophic, I agree that this is a difficult criterion to define/evaluate, but if you look at this chart from NSIDC, it appears that Arctic Sea Ice Extent has increased since 2007:
        http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png

        As such, I’d say that if we had continued to see year over year declines after 2007, I would be more inclined to view it as potentially catastrophic. Furthermore, if I saw a similar decline in Antarctic Sea Ice, as we’ve seen in Arctic Sea Ice, I would also be more inclined to view it as potentially catastrophic.

        [Response: Wow.

        Apparently the only excuse you could come up with to deny that arctic sea ice loss is rapid and catastrophic, is to fall back on the "has increased since 2007" argument. And the only way you'll admit that arctic sea ice is in rapid decline, is if every year is lower than its predecessor.

        So I accuse you of statistical folly. I wonder whether it's rooted in wishful thinking as much as it is in ignorance.

        All geophysical data (including sea ice extent) is a combination of signal and noise. A clear examination of the data (see this), and a detailed analysis of same, shows clearly that the trend continues unabated. Any attempt to claim that the years following 2007 indicate anything else isn't just mistaken, it's dishonest. Perhaps you're simply not being honest with yourself -- but your equivocation about arctic sea ice reveals that you are in denial.

        All you've done is precisely what Anthony Watts does: use short-term random noise as an excuse to deny the trend. As long as you remain unwilling to face, and admit to yourself as well as us, the error of your ways regarding arctic sea ice, perhaps you'll understand why we're reluctant to engage with you on the topic of antarctic sea ice.]

        • Just The Facts

          I am not really sure how to debate you if you choose to twist my statements into what they are not, i.e.;

          I stated that, “I think there is no doubt that there has been a significant and rapid decrease in Arctic Sea Ice Extent during the last 30 years, especially in 2007. ”

          and you replied that, “Apparently the only excuse you could come up with to deny that arctic sea ice loss is rapid and catastrophic, is to fall back on the “has increased since 2007″ argument. And the only way you’ll admit that arctic sea ice is in rapid decline, is if every year is lower than its predecessor.”

          How can you read my statement that, “there is no doubt that there has been a significant and rapid decrease in Arctic Sea Ice Extent” and interpret it such that I “deny that arctic sea ice loss is rapid”?

          [Response: Because of your talk of "it appears that Arctic Sea Ice Extent has increased since 2007" and "if we had continued to see year over year declines after 2007, I would be more inclined to view it as potentially catastrophic."

          Frankly, I am not really sure how to discuss the subject with you if you repeat such an utterly false excuse to avoid the totally obvious conclusion. Because that's all it is: there is no recovery. If you're not a statistician or familiar with data analysis, then perhaps you just don't really know. But the fact is that this is not a matter of opinion, statistically speaking it's 2+2=4. When you say that *maybe* it's only 3 -- Frankly, I am not really sure how to discuss the subject with you.

          And please don't retort that the plain fact "sea ice has increased since 2007" is true -- I know it is. But it's just as much a fact that this is nothing more than random noise -- statistically that really is just 2+2=4. The increase since 2007 is not a recovery, it's a fluctuation, and what has happened since 2007 is exactly what was expected according to the "rapid alarming decline" model.

          I wouldn't be at all surprised if you would have come to a different, in fact correct, conclusion had you just looked at the data -- but you got the wrong idea from somebody else, like Anthony Watts.

          And that's what this post is about. Anthony Watts should know that all this talk of "recovery" is mistaken to the point of idiocy, because he has been told. Repeatedly. Yet he persistently, consistently, finds an excuse -- often an embarrassingly lame one -- to deny the obvious conclusion. That's not a skeptic at work, he's in denial.

          Honestly, many of your statements lead me to believe that you want to find the truth and are trying to keep an open mind. But some of your statements -- specifically about sea ice "recovery" -- make progress in discussion very difficult.]

        • Just The Facts

          But again, you are arguing statements that I have not made. You state that, “But some of your statements — specifically about sea ice “recovery” — make progress in discussion very difficult.” But I have not used the word “recovery” at all in my comments. I made a factual statement that, “it appears that Arctic Sea Ice Extent has increased since 2007″. A recovery would connote that September Arctic Sea Ice has returned to its pre-2007 or arguably 1979 levels, neither of which have occurred. However, the fact that Arctic Sea Ice has increased in the last several years, does make me question whether the decline in Arctic Sea Ice is potentially catastrophic versus being significant.

          I am not Anthony Watts, if you want to debate him, you know where to find him. If you want to debate me, then you should address my statements, not the statements of others.

          [Response: You protest that you never used the word "recovery." OK fine. But be honest; you're hiding behind semantics. You did not just state "make a factual statement" as though it had no implication. You stated it in the context of the trend in arctic sea ice, which implies that it's relevant. Which it is to you, it's your very reason for doubt, you even say "the fact that Arctic Sea Ice has increased in the last several years, does make me question whether the decline in Arctic Sea Ice is potentially catastrophic versus being significant"

          I've tried to make it clear that the increase since 2007 is irrelevant to those questions. That's not my opinion. It's a fact. The *potential catastrophe* is the rapid, alarming, trend, which has continued unabated with no sign of stopping or even slowing down. Seriously -- read this.

          The entire "since 2007" argument is a useless irrelevancy. As long as you continue to give it as a reason for question, we're gonna have a hard time communicating. But if you can stop clinging to it, we might have some very interesting things to say.]

        • Justthefacts,
          As scientists, what we must be interested in is predicting future behavior. It is in that sense that Tamino is saying that the uptick in ice extent since 2007 is not meaningful. It is rather like a dead-cat bounce after a 1000 point plunge by the Dow–the fact that it then rises 100 points does not indicate a rally in stock prices. I am afraid that the term “catastrophic” is simply not a meaningful term. Of course, the ice will not collapse all at once. Rather, it looks as if it will continue its death spiral, but I hardly see how this merits a sigh of relief.

        • Just The Facts

          For conversations sake, let’s put what occurred in 2007 and beyond on the back burner, and see if we can agree that there is a clear and substantial downtrend in Arctic Sea Ice;
          http://nsidc.org/data/seaice_index/images/n_plot_hires.png

          and a small uptrend in Antarctic Sea Ice;
          http://nsidc.org/data/seaice_index/images/s_plot_hires.png

          which result in small downtrend in Global Sea Ice:
          http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/global.daily.ice.area.withtrend.jpg

          I really don’t want to get into a semantics exercise, my goal is just to discuss and ideally reach agreement upon the facts.

          [Response: Mine too.

          I agree there's a clear and substantial downtrend in Arctic sea ice, and that there's a small uptrend in Antarctic sea ice. I would characterize the decline of global extent as "clear and substantial" rather than "small," but to see that you need to transform raw data (with its annual cycle) into anomaly.]

        • Just The Facts

          Since I have been using the NSIDC Monthly Sea Ice Extent Anomalies Charts, I figured that I’d use the corresponding data to calculate Global Monthly Sea Ice Extent Anomalies:
          ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/N_09_area.txt
          ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Sep/S_09_area.txt

          I first recreated the NSIDC Northern and Southern Sea Ice Extent Anomalies Sept 2010 charts:
          http://i54.tinypic.com/30uby9d.jpg
          http://i53.tinypic.com/nbxfs6.jpg

          to check the data and methodology, here are NSIDC’s originals for comparative reference:

          http://nsidc.org/data/seaice_index/images/n_plot_hires.png
          http://nsidc.org/data/seaice_index/images/s_plot_hires.png

          I then merged the two data sets and created a chart for Global Sea Ice Extent Anomalies Sept 2010:
          http://oi55.tinypic.com/2lmq4qw.jpg

          Based on my calculations, the slopes of the trendlines are as follows:
          Northern Sea Ice Extent Anomalies Sept 2010: Slope = -11.3% per decade
          Southern Sea Ice Extent Anomalies Sept 2010: Slope = 0.8% per decade
          Global Sea Ice Extent Anomalies Sept 2010: Slope = -2.6% per decade

          I am not going to try to define the substantiality of downward trend in Global Sea Ice Extent, rather I’ll state that the downward trend in Global Sea Ice Extent is significantly larger than the upward trend in Southern Sea Ice Extent and significantly smaller than the downward trend in Northern Sea Ice Extent. If anyone would care to check my math, it would be most welcome.

    26. Just the Facts,
      Here is another site that has good long term temperature records, and other, from around the globe.

      http://www.rimfrost.no/

      I used that site, plus the Central England & Debilt sites to reconstruct some long term central & western European temperature anomalies. After running a 40 year Fourier convolution filter through it, a interesting almost periodic ~50 year signal showed up. Ditto using the shorter Hadcet data.

      http://www.imagenerd.com/uploads/lt-temp-1800-2008-14-9ZSv8.gif

      Didactylos, it is even more unwise to ignore what your competitor is saying or doing. Besides how much is the “official” data filtered? Even a simple average can be a filter, not to mention “homogenization”.

      • “Besides how much is the “official” data filtered?”

        *sigh*

        If you want to know these things, you need to read what the authors have published about their data. This is elementary. Why are you so excited by it?

        It disturbs me that you are poking around with data but have neglected these fundamentals. As for your “insights” – they gave me a laugh, but don’t try to publish them unless you really enjoy rejection!

    27. “Just The Facts” must be severely deluded if he genuinely thinks that anybody is trying to hide the Antarctic data. But that’s pretty much the very definition of “denier”.

      And again he can’t see any warming in the global data. May I recommend an eye test, Mr. “Just The Facts”?

      Also, I think I see a flaw in your chosen name. You seem to be immune to facts in any shape or form. Shall we call you “Just the convenient facts”? And note: this is an insult, not an ad hominem. Please learn the difference.

    28. Interesting post, Tamino. I am curious about why the interval in your prediction figure doesn’t flare out at the ends.

      [Response: In this case that effect is small, and I was lazy enough to consider it negligible.]

    29. Just the Facts
      One criteria you could use would be to look at the area above or below sea ice levels over time (i.e. days & amount of ice) similar to temp-days used by utilities. Looking at the Arctic sea ice time series:

      http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/sea.ice.anomaly.timeseries.jpg

      you could compute the anomaly area, say below the 0.5 & 1 mill-sq-km lines, as a metric, on a per yearr basis. I personally think this might be a better measure then just the peak & valley points, which can be of very short duration.

      • Eyeball Mark I claims you’ll still find a robust trend of declining sea ice. But go ahead–do the math.

        I actually did a similar (though simpler) exercise, computing annual part-year means using the JAXA data. Kind of fun, but there’s really nothing to disagree with Tamino’s point in this post.

        Arctic summer ice is going to be gone. It’s just a matter of when.

    30. “the best predictor of future behavior is past behavior: the [downward] trend continues.”

      An unequivocal statement about Anthony Watts.

    31. Susan Anderson

      It is fascinating that people are unwilling to acknowledge (in the case of the campaign to mislead) or understand (in the case of their fellow travelers) that an exceptional year does not make a new starting point, but indicates various possibilities. In an overall rising trend (say, since observations began and with more focus as there began to be more observations) an exceptional year can be just that, or it can be a pointer for gathering exceptions which will become the norm. As warmer years cluster towards the end of the oughts, 1998 is fiercely defended as the baseline for all observations. The new high years (2005, 2010, 2011 and probably 2012 if I understand correctly) will be claimed to be the new lows as soon as enough time has elapsed that people can be duped into thinking that a slight downward return to normal is a slippery slope. How hot does it have to get for how many years before reality slips in?

      1998 has been used to create a misleading conversation about cooling, and linked to scientific interest in the 70s about possible cooling which is claimed to have been just like warming, which it wasn’t. (The speculation peaked in MSM, but scientists kept on observing and reporting, being firmly based in reality.) Now 2007 is being used as the new Arctic “low” when actually it was an exceptional “high” (low being high, if you follow me, in describing ice extent). In addition, the obviousness of volume change is buried in surface area, though we don’t live in a two-dimensional world.

      Scientists’ tendency to be careful with the truth is constantly used against them. A former weather presenter with a huge fan club should not be treated as a prophet. I understand Watts’ work on weather stations was original (and failed to prove what he thought it would), but most of what he does is reinterpret in a highly selective and political way information that is available in the original with relatively little effort, and does not say what he claims it does. No matter how often it is pointed out that this is NOT skepticism, it continues to be regarded as truly skeptical.

      True skeptics look at real information and question everything. These fake skeptics question all of mainstream science and world scientific organizations, and real-world data, but give a free pass to anyone they would like to use to destroy conclusions about reality that we all need to see and understand. They inflate what they’d like to believe, and never stop attacking reality.

      It is a weird world where people can ignore what is all around them and hew loyally to a world which in the end will not stop one drought, flood, fire, migration, seasonal change, or starving population or help the victims. They claim to be concerned about money, but are not at all interested in the ballooning costs of disaster relief as the real world breaks in to their fantasy.

      As to visiting WUWT I avoid it for aforementioned reasons and also because I understand if I click there it will be counted towards his popularity, which he regards as an indicator of his truthiness.

      • Ray Ladbury

        Susan, I’m afraid I’m with you. I’ve never learned anything by visitint WTFUWT, and I’m afraid my mother brought me up too well for me to take delight in the antics of idiots in their natural environment.

        • Susan Anderson

          Thanks, but sheesh, I should have realized I was revisiting 2010. I am grateful for all the crosslinks, references, and information transmitted via RealClimate, as it is always fun to be pushed to learn even if the result is depressing.