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Never Mind The Area, Feel The Thickness

February 28, 2017

By Paul Homewood




For years, discussion of Arctic sea ice has revolved around extent. Indeed NSIDC’s regular monthly Arctic Sea Ice News talks about little else, particularly when there is an unusually low figure.

However, when extents are not so unusually low, the Arctic obsessives switch the goal posts to thickness/volume.

There is one problem however – there is no reliable measurement data around to track it.


As the Greenpeace activist, and part time NSIDC scientist, Julienne Stroeve admitted, “satellite measurements [of thickness] are not continuous in time, not continuous in space.” (See BBC interview at 4 mins in here).

To get around this slight problem, the obsessives turn to the PIOMAS Arctic Sea Ice Volume Reanalysis, shown above.

But this is not based on real data, though they seem to delude themselves that it does. Instead, it is a numerical model with components for sea ice and ocean and the capacity for assimilating some kinds of observation.

Or as someone put it, a model to estimate what area and thickness would have been elsewhere had we measured them.


Now PIOMAS might have its uses, and it may have some relation to reality. But we need to see what the PIOMAS team themselves say about its accuracy:


PIOMAS has been extensively validated through comparisons with observations from US-Navy submarines, oceanographic moorings, and satellites. In addition model runs were performed in which model parameters and assimilation procedures were altered.  From these validation studies we arrive at conservative estimates of the uncertainty in the trend of  ± 1.0 103 km3/decade. The uncertainty of the  monthly averaged ice volume anomaly is estimated as ±0.75  103 km3. Total volume uncertainties are larger than those for the anomaly because model biases are removed when calculating the anomalies. The uncertainty for October total ice volume is estimated to be  ±1.35 103 km3


Last October’s ice volume was 5500 cu km, so the uncertainty is a massive 25%.





It is hard to see how any significance can be read into recent trends, when error margins are so large, even assuming the model is reliable in the first place.

  1. Broadlands permalink
    February 28, 2017 6:50 pm

    “It is hard to see how any significance can be read into recent trends, when error margins are so large, even assuming the model is reliable in the first place.”

    Yes, and isn’t that true for the “global” temperature data as well?

  2. Bloke down the pub permalink
    February 28, 2017 7:09 pm

    ‘It is hard to see how any significance can be read into recent trends, when error margins are so large, even assuming the model is reliable in the first place.’
    Especially when the trend for this decade would appear to be upwards.

  3. AlecM permalink
    February 28, 2017 7:33 pm

    Arctic ice extent has fallen a bit because of the extra ocean heating in the Pacific from the real AGW, which is extra Asian aerosols decreasing cloud albedo.

    The Arctic sea gets warmer so melts peripheral ice.

    The Antarctic gets extra snowfall via the Hadley Cells, so its peripheral sea ice grows.

  4. February 28, 2017 7:44 pm

    Arctic ice extent is cresting now. With 2 weeks until maximum, it is well ahead of 11 years ago.

  5. February 28, 2017 8:25 pm

    “There is one problem however – there is no reliable measurement data around to track it.”

    Not a problem for the alarmists, in fact an advantage, more scope to make up figures.

    • bea permalink
      February 28, 2017 8:38 pm

      If it is not one thing with CAGW it is another: round and round.

      The thought processes of these plodders remind me of the little boy who invented a perpetual motion machine:

      “Father, I would make up a great wheel, and hang it up like a water-wheel; at the top I would hang a great weight and at the bottom I would hang a number of little weights; then the great weight would turn the wheel half round, and sink to the bottom because it is so heavy: and when the little weights reach the top they would sink down because rhey are so many; and thus the wheel would turn round for ever.”

  6. nightspore permalink
    February 28, 2017 9:13 pm

    There must be some sort of positive relation between volume and minimum extent. So it is passing strange that the latter shows no net change over the past 10 years (2007 to 2016), while the former is supposed to be in freefall.

  7. February 28, 2017 9:25 pm

    Do not forget that most of the graphs start at a peak, not at a trough.

  8. Tom Dowter permalink
    February 28, 2017 9:38 pm

    The three common measures of sea ice are extent, area and volume. The annual averages for all 28 periods of ten years from 1979-2015 show a negative trend for the Northern hemisphere for both extent and area. Only 25 of those for sea ice volume do. So, it doesn’t really matter which measurement you use: the trend is still downwards. (The three periods of rising volume lie between 1880 and 1991, so it is hardly recent data).

    The Antarctic is very different. There are only 5 such periods for area and 4 periods for extent that show a falling trend.

    Of course, there is a lot less sea in the Antarctic, but it is strange how rarely it is mentioned in the context of sea ice.

    • February 28, 2017 9:59 pm

      Tom, when you look at the annual averages for Arctic extents during the satellite era, you get a graph that looks like this:

      Yes, it shows a decline, but it was quite gentle to 1994, then dropped sharply down to 2007, and has been on a plateau, or slightly rising since.

      • Mike Jackson permalink
        February 28, 2017 10:33 pm

        And why assume that a 35 year period is typical just because it fits in with a preconception?

      • February 28, 2017 11:00 pm

        Mike, I don’t say this period is typical. Naval ice charts over centuries show a quasi-60 year fluctuation, of which the current period is a part. It happens to be the part we are experiencing.

      • Tom Dowter permalink
        March 1, 2017 5:59 am

        Your comments on a 60 year cycle for Arctic sea ice are interesting. I have long been aware of an apparent 60 year cycle for global temperatures.

        For example, if we use HadCRUT4 as our dataset, then 1850-1879 shows a warming, 1880-1909 shows a cooling, 1910 to 1939 shows another warming, 1940-1969 shows a cooling and 1970-1999 shows yet another warming.

        What we appear to have is a sixty year cycle superimposed on a longer term warming, (as well as other things). This cycle would also explain the “hiatus”, i.e. the substantial reduction in warming post 2000.

        I am a little puzzled by your assertion that since 2007 sea ice has been on a rising trend. The average for each year between 2007 and 2016 has been on a downward trend for both extent and area.

        Note: my trends are the best fit straight line covering the data, achieved by minimising the sum of the squares of the deviations between the straight line and the actual data, (i.e. standard linear regressions).

      • AndyG55 permalink
        March 1, 2017 7:04 am

        The Icelandic sea ice graphs show an rough 60 year cycle, even during the LIA.

      • March 1, 2017 12:31 pm

        Tom the chart shows for each year the average of 365(6) days.

      • Gerry, England permalink
        March 1, 2017 1:59 pm

        Those pre-eminent in Arctic ice – ie have nothing to do with the IPCC – refer to a 60-65 year oscillation in the Arctic ice. So until there is satellite data for that length we are only seeing part of a cycle. Knowledgeable ice folks also say that the poles are asynchronous so if the Arctic has hit its low point, the Antarctic has hit its peak. Which does seem to be the case but a few more years will make it clear.

      • March 1, 2017 2:48 pm

        Thanks Gerry for commenting. Among those knowledgeable folks are the Russians at AARI. See post of Arctic Ice Self-oscillating system.

  9. February 28, 2017 10:46 pm

    We’re supposed to think it was always around the 1979 level until it dipped, but that’s just deceptive nonsense.

    • bea permalink
      March 1, 2017 7:32 am

      Once again, the line from “Little Rascals”:

      “The ‘Blur’ hasn’t been beaten since the beginning of time, five years ago!”

  10. March 1, 2017 3:39 pm

    Come on. It is historically low. The margin of error applies to them all.
    Not saying the Arctic ice extent is long-term significant or related to fossil fuel burning. Just it’s low and the warmists can legitimatly say so.

    • Tom Dowter permalink
      March 1, 2017 6:45 pm

      Exactly! Sceptics will never win the climate war if they fight on grounds of the warmists’ choosing.

      It would be much better to focus on their weaknesses. However, it is important not to exaggerate these. Nothing destroys the credibility of an insurgent so much as being proved wrong, even if only partially so.

      Once you have been proved wrong, your credibility, even when you a right, is of no account. Get a reputation as a crackpot and you will never recover.

  11. March 3, 2017 2:35 pm

    Reblogged this on Climate Collections.

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