Sea Ice: 2012, A Prediction

October 13, 2011


Having seen the embarrassing ruby slippers nonsense about sea ice “recovery” from Joe Bastardi, Anthony Watts, and “Stephen Goddard” crash on the hard rocks of reality, how about let’s give someone a chance who has actually been accurate?

Tamino at Open Mind gave me permission to repost his recent sea ice piece:

The numbers are in from the National Snow and Ice Data Center (NSIDC) for Arctic sea ice extent and area in September 2011. The average September extent came in at 4.61 million square kilometers. It was back in October of 2010 that Ipredicted this year’s September extent would be 4.63 million square kilometers. That prediction turned out to be right on the money.

Before you’re too heartily impressed, bear in mind that my prediction was 4.63 +/- 0.9 million km^2. It was a simple statistical prediction, based on continuing the existing trend into this year. Clearly this year’s evidence indicates: the trend continues. That’s why my prediction was correct. But the error range (the range in which we expected the result probably to fall) was sizeable. The reason my prediction was so close to the final result is: I got lucky.

Or maybe not. It’s good luck that the prediction was so close. It’s bad luck — for all of us — that the trend continues. It’s because of global warming, and that’s bad. For all of us.

In July I updated the forecast to include information from both the extent and area figures for June of this year. That yielded a prediction of 4.66 +/- 0.66 million km^2, not much different from the original prediction. In yet another update in August, a model using past September extent and this year’s extent from July as well as area from June and July predicted 4.22 +/- 0.62 million km^2. However, I also noted that I guessed the odds were about 50-50, and in comments a reader asked whether my actual expectation was therefore 4.3, to which I agreed. In either case the prediction was also correct (its error range included the final result) but didn’t turn out nearly as good as the original trend-only prediction either. That’s statistics for you.

Here’s the final result for this year, which takes over 2nd place for all-time low extent, together with predicted values (from continuing the trend) for the next three years:

The prediction for next year’s NSIDC September average is 4.43 +/- 0.89 million km^2.

This year did not set a new record, the 4.30 million km^2 September average (NSIDC) from 2007 is still the lowest yet observed. Neither did it set the record for daily minimum in the JAXA data set, for which this year came in 2nd as well. But according to data from the University of Bremen this year did break the 2007 record.

As for sea ice area rather than extent, 2011 did break the record according to data from Cryosphere today. Perhaps the most meaningful metric for global warming is sea ice volume, which according to PIOMAS also set a new record low.

In fact, in spite of the quite steady decline of Arctic sea ice extent and area, the volume has declined even more steadily because the ice is thinning as well as covering less area. The trend is evident from a graph of sea ice volume anomaly:

Perhaps most startling is that every day this year has shown a lower volume than the same day for any previous year:

One other fact deserves mention. As pointed out on RealClimate, Arctic sea ice is declining all throughout the year, not just during its summer minimum. This has a profound effect, especially during summer (June/July/August), the months of greatest solar insolation, because what used to be covered with highly reflective ice is now highly absorptive ocean. This increases the heat input to the Arctic (ice-albedo feedback), one of the reasons that the Arctic is warming so much faster than the globe as a whole.

Whatever month one chooses, the trend in Arctic sea ice is one of rapid decline. The latest data indicate that the trend continues. The reason is: global warming.

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7 Responses to “Sea Ice: 2012, A Prediction”


  1. [...] Update (13 Oct): This just in from Climate Denial Crock of the Week: ‘Sea Ice: 2012, A Prediction’. It includes excellent clips of erroneous statements of deniers like Bastardi, Watts, and Goddard; [...]

  2. mrsircharles Says:

    +1

    Great article!

    I mean, just take a look at the climate change denier blog site “real science”. Those guys are so convinced they’d be right, even when the owner and lead author had to correct two of his headlines (and I really don’t usually visit that crap site) because I (and I’m not a scientist) proved him – making a setup – wrong by multiple factors, that they don’t bother re-posting ignorant waffle again and again.

    Those (including the discredited WUWT => Wott’s Up With That?) are the sites people like rush or Trollo are taking their “information” from.

    In contrast – when producing evidence from multiple credible scientific sources – bloggers like Peter Sinclair are defamed as “paid propagandists” or even part of a “conspiracy”.

    Jesus Christ! Lord, please let rain some brain!

  3. otter17 Says:

    I particularly like that second figure showing the next few year’s projections with error bars. Quite informative.

    • sinchiroca Says:

      The error bars look a bit large to me. If they are conventional and represent single standard deviations, then if extended backwards, we’d expect only two-thirds of the existing points on the curve to fit within those error bars. But my eyeball estimate is that only three of the 35 previous data points are at the extrema of the error bars. This suggests that the errors should be maybe two-thirds of their present size. I suspect that the author is being conservative. Or perhaps there’s something about the data I’m not aware of.

    • otter17 Says:

      Yeah, in the comments from his article Tamino lays out the statistical method used to develop the error bars. I just like that he went the extra mile to include uncertainty. Tamino has published in peer-reviewed journals as I recall.

  4. pendantry Says:

    With curves like those demonstrating terminal decline, that anyone can talk about ice ‘bouncing back’ reveals either cluelessness beyond the pale or ulterior motives.


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