Thursday, March 26, 2015

Some Cold Facts

The right-wing and denialist blog suyts space has a recent post attempting to convince the gullible that no sea ice has melted since 2001. This silly notion has been occasionally making the denialist blog-rounds for some time. Oddly enough, the same blog had a similar post on the same topic over a year ago, claiming that there had been no ice melt since 2004 -- and the level at which we had a "flat trendline" then was lower than it is today. Apparently, new ice has appeared to raise the level that had existed between 2004 and 2013. Imagine that.

What does this mean? It means the loss of global sea ice is a chaotic process, even though it has a definite long-term trend. I suspect the author of suyts space is desperate to distract people from the fact that Arctic ice has just had its lowest winter maximum ever. It is important for purveyors of fantasy to get out ahead of reality whenever possible.

Denialists these days are obsessed with the fact that the area covered by Antarctic sea ice in the winter has been slightly greater the last few years than it used to be. What they won't admit is that this phenomenon is known to be caused by the same forces that are causing the Arctic ice collapse, that is, "global warming." Indeed, climate denialists try to imply that the slight increase in seasonal Antarctic ice somehow "disproves" the existence of climate change, rather than being a symptom of it. I'll deal with that in a future post as well.

In the meanwhile, I decided to create some global sea ice graphs of my own, and I found a wonderful source for data, the National Snow and Ice Data Center. This post and at least the next two will use data from that source.

Below is the first in a series of sea ice graphs. It is the average yearly sea ice area from 1980 through 2014. I have added a linear trendline. In any chaotic dataset, it is always possible to cherry pick sub-spans which allow one to create flat trendlines (which is what we see happening on suyts space), or even trendlines that slope in the direction opposite to the overall trend (suyts could have done that by starting at the point where his 2004 trendline began, and running up to the current day). Doing so, however, is an exercise in political propaganda, not a scientific practice.

In the graph below, you will notice the actual ice area sometimes goes above the trendline, and sometimes goes below the trendline. This is normal for any chaotic process. You will also notice that the trendline is trending unequivocally down. That's because global sea ice is decreasing.

fig 1 - Yearly sums of Arctic average ice area and Antarctic average ice area

You will also notice that the divergences above and below are getting larger. This is also normal for a chaotic process that is becoming increasingly unstable, signaling an impending total collapse.

The last two years diverge particularly high -- that is, the average level of global sea ice has been higher for the last two years. 2006, 2007, and 2011 diverged particularly low. Denialists will stress the last two years and ignore the others, because that’s how they roll. (They are irrational in the extreme.) Denialists will claim that climate scientists likewise concentrate only on the extremes below the trend line, but that is false, since the high numbers are also due to climate change. Human production of greenhouse gasses is destabilizing the climate in a variety of destructive ways.

Let me also point out, it makes little sense to sum up northern and southern hemisphere ice in this way. Sea ice in the north and south are subject to entirely different processes. The north is a sea surrounded by land which is covered by steppes. The south is a continent covered in an ice sheet, surrounded by water. Adding the sea ice from these two areas is like adding the scores of the Bears and the Cubs into a “Chicago sports score.” Not only does this score tell you nothing meaningful, but it excludes the White Sox, the Black Hawks, and the Bulls. In a similar way, we are leaving out land-based glaciers, the Greenland ice sheet, and the Antarctic ice sheet -- as well as ignoring the volume of the sea ice, which tells us how much ice there actually is.

If we are to concentrate only on sea ice, and only on area, I will have a recommendation for a much better way to do that in my next blog post.

Below are two more graphs, showing the sum of each year’s minimum sea ice, and maximum sea ice – that is, each year’s Northern Hemisphere max plus that year’s Southern Hemisphere max, or Northern plus Southern hemisphere min.

On these graphs, as on the graph above, the scale at the left is in millions of square kilometers. The scale differs on each graph in order to fit the graphs to a consistent size, but I can create them to a consistent scale if readers want to see that.

fig 2 - Yearly sums of Arctic Minimum and Antarctic Minimum ice

fig 3 - Yearly sums of Arctic Maximum and Antarctic Maximum ice

As with the yearly average graph, I have added linear trendlines. You can again see rapid collapse, particularly in the yearly minimum. This will become even more apparent when I separately graph each hemisphere. You an also see that the yearly maximum is trending rapidly down even with the Antarctic sea ice winter maximum increasing, because the Arctic ice is decreasing faster.

As with the “Average” graph, the last two or three years have been significantly above the trendline. This means nothing, because this is a chaotic process. You can see the Minimum graph shows the final year (2014) as lower than the year previous (2013) – the brief recent upward divergence has already ended, which is why this winter’s (2015’s) Arctic maximum has set a new record low (which will affect the graphs next year).

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