Why Doesn't Anyone Mention the Record Growth of Sea Ice Around Antarctica?

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Typical of the commentaries on sea ice is this by Harold Ambler, published, of all places, in the Huffington Post, on January 3, 2009:

P.S. One of the last, desperate canards proposed by climate alarmists is that of the polar ice caps. Look at the "terrible," "unprecedented" melting in the Arctic in the summer of 2007, they say. Well, the ice in the Arctic basin has always melted and refrozen, and always will. Any researcher who wants to find a single molecule of ice that has been there longer than 30 years is going to have a hard job, because the ice has always been melted from above (by the midnight Sun of summer) and below (by relatively warm ocean currents, possibly amplified by volcanic venting) -- and on the sides, again by warm currents. Scientists in the alarmist camp have taken to referring to "old ice," but, again, this is a misrepresentation of what takes place in the Arctic.

More to the point, 2007 happened also to be the time of maximum historic sea ice in Antarctica. (There are many credible sources of this information, such as the following website maintained by the University of Illinois-Urbana: http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.anom.south.jpg). Why, I ask, has Mr. Gore not chosen to mention the record growth of sea ice around Antarctica? If the record melting in the Arctic is significant, then the record sea ice growth around Antarctica is, too, I say. If one is insignificant, then the other one is, too.

So let's take a look at ice trends in the Arctic and Antarctic (data from the National Snow and Ice Data Center). The graphs show ice extent compared to the long term (1979-2000) average for that month. To match up the seasons, I offset the Antarctic data by six months. We start off in midwinter (January in the Arctic and July in the Antarctic).

In the Arctic, we see a decrease every single month. In the Antarctic, there is indeed an increase each month. But there's more to the story than that. There are those +/- figures. What do they mean?

Since the data have random fluctuations, the slope that best fits the data isn't guaranteed to be the true slope. It's possible a random cluster of high or low points affect the slope and a longer data run might show a different slope. That's what the +/- numbers indicate. For example, the Arctic data for December 2007 show a decrease of 3.3 per cent per decade, plus or minus 0.7 per cent. Usually statisticians use 95 per cent as their reliability criterion. So if we had a very large number of similar data sets that gave us those results, and we could determine the true slope* (say by getting a much longer run of data), we'd expect that 95 per cent of the time, the true slope would show a decrease between 2.6 and 4.0 per cent per decade.

(*For experimental purists, we never know the true value of anything we're trying to measure. We just get closer to it by gathering more and better data. So another way of putting it is that if we had a large number of similar data sets, and we kept on adding data to them, 95 per cent of the time, the slope would show a decrease between 2.6 and 4.0 per cent per decade.)

Now, note that in the Arctic, the error margin is less than the slope for every single month. In every single month, the slope is at least 2.5 times greater than the error margin. And in the summer, when melting is greatest, the slope is greatest, reaching a whopping 11.1 per cent in September, with a margin of error of only 3.3 per cent. That means the true value is almost certainly between 7.8 and 14.4 per cent. Decreasing an ice mass of millions of square kilometers at a rate of 7.8 to 14.4 per cent per decade is phenomenal. And note that the ice area decreases from year to year every month. That means what melts in the summer doesn't re-freeze in the winter on the average. Also note that the trend line does not include the big drop in 2007.

That's why the concern about losing "old ice" is serious. Year-old pack ice is about 2 meters thick but multi-year ice is several times that. Old ice melts slower than new ice because it's thicker. So as more and more of the ice in the Arctic is replaced by young ice, the summer melting will accelerate. It's probably true, as Ambler claims, that the turnover time of a water molecule in Arctic ice is only 30 years or less. Decreasing the turnover time to a few years would be pretty significant.

Now let's look at the Antarctic. The winter data show ups and downs of similar size as the Arctic data, but the swings in the summer are pretty wild. In every single month, the error margin is at least as large as the slope, and in December, it's four times larger. For January, the slope of the data indicates an increase of 1.9 per cent per decade, with an error margin of 5.3 per cent. In other words, there is a 95 per cent chance that the long-term average, assuming the data continue to show the same trends, lies somewhere between an increase of 7.2 per cent and a decrease of 3.4 per cent. Basically the Antarctic winter data show level trends and the summer data are so noisy that the best fit slope has very little statistical significance.

So, to answer Ambler's final question:

Why, I ask, has Mr. Gore not chosen to mention the record growth of sea ice around Antarctica? If the record melting in the Arctic is significant, then the record sea ice growth around Antarctica is, too, I say. If one is insignificant, then the other one is, too.

The answer is simple. The Arctic decrease is statistically significant, and the Antarctic increase is not. This is Stats 101. Ambler is flat out wrong. Not all trends are equally statistically significant.

Let's take a look at some more statistics. Here's the anomaly month by month.

Now that does look impressive there at the end, until you look at the horizontal scale and see that all those spikes are for a few months in 2008. But notice that between two of the highest spikes are some striking lows (not noted by Ambler for some reason).

Actually, this is a pretty much worthless graph. The data are just fine, but without knowing the average ice extent for each month, it's impossible to interpret. That's why the month by month anomaly graphs are so much more informative.

So here's a graph actually showing Antarctic ice extent.

See how, for 2008, the line just nudges above the 16 million square kilometer line? That's it. That's your "record growth of sea ice around Antarctica" that Al Gore didn't mention in An Inconvenient Truth. Of course, since the film came out in 2006, Gore would have to have been pretty prescient to have mentioned it. Even if we give denialists the benefit of the doubt and suggest that Gore had access to 2006 data, 2006 was not a record.

Okay, now let's look at the Arctic. There's an interesting, roughly five year cycle in the yearly maxima, but even to the unaided eye there's a steady decrease in both maxima and minima.

And He-e-e-re's Boortz!

I like Neal Boortz because he has no qualms about labeling 9-11 and chemtrail conspiracy believers as idiots and Religious Right extremists as extremists and prudes, but offsetting those virtues - sort of like intellectual carbon offsets - are his dumb comments on global warming. So here he is on January 6, 2009:

This is going to be upsetting news to many of you out there. Global sea ice levels are now equal to those recorded 29 years ago. This is according to the University of Illinois's Arctic Climate Research Center. Why only since 1979? Because that was the first year we started recording this data. But for you people out there howling over the melting sea ice and the endangered polar bears .. now what? Sea ice is at the same level as almost 30 years ago.

The link goes, not to the original research report, but to a news release that reproduces this graph:

Incidentally, the IT-illiterate idiots who output line graphs as .jpg files should be set loose on an ice floe themselves.

The upper graph shows daily sea ice in blue and average sea ice in lavender. The lavender curve is the same every year. The bottom curve is the daily ice anomaly, the difference between the two upper curves. Note first of all that the upper curves have two peaks corresponding to ice maximum in each hemisphere. They peak about April and October. Why? Heat lag. It takes time for the earth to warm up and time to cool down, and summer warming doesn't overtake ice formation until well after the equinoxes.

Now with global sea ice seesawing annually between 15 and 24 million square kilometers, you can always find a point in any given year where sea ice equals what it was in 1979. But we can also see that there hasn't been a 23-million peak since 1994. The only years with peaks as low as 21 million are 2001 and 2007. Beginning about 1995 the global sea ice totals show an overall decline.

The bottom curve, the daily anomaly, is useful only for defining long term trends - the day to day fluctuations mean very little. But it shows an obvious decline beginning in 2001. The decline starts so soon after the 2000 cutoff for the long term average that it's worth wondering whether the long term average masks a decline, if using an average between say 1979 and 1990 might show a different result.

And actually, the 2009 results aren't equal to 1979. The 1979 anomaly is quite a bit higher overall than 2008. The year end points are nearly equal, that's all.

Boortz goes on:

Oh and just so you know, sea ice doesn't affect ocean levels. So if you are concerned that all of this sea ice is going to melt and we are going to have those apocalyptic rising oceans - as promised by Owl Gore - Get over it. Try this little experiment. Put water and ice into a bowl. Make sure that the water is right up to the brim of the bowl. When the ice melts the water will not rise and overflow the bowl. Don't get a government-funded scientist to do this for you. He will somehow come up with a different result, so do it yourself.

This is true and there are poorly informed people on both sides who need this, considering the date, epiphany. But no climate modeler claims that melting sea ice will raise sea level. Go ahead. Find just one. What will raise sea level are thermal expansion of the oceans and melting of land glaciers and ice caps above sea level. And "West Antarctica," meaning the portion in west longitude, including the Antarctic Peninsula, is the portion that is

  1. Warming most rapidly.
  2. Prone to sudden retreats of its ice cap as shown in the geologic record.

Of course, we should go easy on Boortz. He was probably home schooled or went to a private school, rather than having the benefit of a government-run schooling.

But Antarctica is Getting Cooler!

Well, here's the data from NASA. The map shows surface temperature, not air temperature. Draw your own conclusions. Hint: step back and tell me whether the picture is red or blue.

Now here's a map you probably won't see on any climate change skeptics' blog any time soon. It shows regions of snow melt in Antarctica by year of first occurrence.

Notes on Arctic and Antarctic Ice

Sea ice is measured from satellites, which is why data extend back only to 1979. The definition of sea ice is any area with at least 15 per cent ice cover. So it's perfectly possible to have big day to day variations because ice may disperse and then re-aggregate due to winds and currents.

Antarctic ice oscillates between a low of 2 million and a high of 16 million square kilometers. Arctic ice ranged from 8 to 16 million square kilometers in 1979 and 4 to 15 in 2007. The reason basically is that the Arctic is confined and the Antarctic is not. Sea ice that breaks off Antarctica in the summer can be carried to warmer latitudes and melted. Sea ice that breaks off the Arctic ice pack mostly continues to circulate in the Arctic Basin and disperses more slowly. One reason that there was a precipitous drop in 2007 was that winds and currents pushed unusually large amounts of ice out through the Norwegian Sea.

To be sure, climate modelers are perplexed by the differing responses of the Arctic and the Antarctic. In general, the Arctic is responding faster than the climate models predicted and the Antarctic is responding more sluggishly.

There are lots of legitimate and serious questions about climate change that all researchers in the field readily admit. What convinces me of the reality of climate change, despite the uncertainties, is that the comments put out by climate change denialists are absolute, unmitigated garbage. We find distortion and misuse of credentials, publication of counterfeit papers, and scientific illiteracy of all sorts. This junk is on a par with the creationism of Michael Behe and Darwin's Black Box. Comparing the long term steady decrease of Arctic sea ice with a tiny peak in Antarctic sea ice is statistical illiteracy of the worst kind.

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Created 04 January 2009;  Last Update 30 August, 2011

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