Jeff's Lunchbreak: Climate Change - Arctic Sea Ice Extent

I recently had a conversation with an acquaintance regarding climate change. He was a denialist, and one of his arguments, while a familiar tactic, was a new one to me on the specifics - that 2013 had seen a dramatic increase in Arctic sea ice extent, indicating that the global warming trend had reversed. After doing a bit of Googling, I found similar claims in some of the standard denialist sources. For example, a recent article in The Telegraph by Hayley Dixon carried the headline, Global warming? No, actually we're cooling, claim scientists. The synopsis right under the headline read:

A cold Arctic summer has led to a record increase in the ice cap, leading experts to predict a period of global cooling.

The opening two paragraphs of the actual article are quoted below.

There has been a 29 per cent increase in the amount of ocean covered with ice compared to this time last year, the equivalent of 533,000 square miles.
In a rebound from 2012's record low, an unbroken ice sheet more than half the size of Europe already stretches from the Canadian islands to Russia's northern shores, days before the annual re-freeze is even set to begin.

To be charitable, the numbers being claimed seem to be relatively accurate. The problem lies in the interpretation.

My first reaction to hearing the claim from my acquaintance was to go looking for the data to see for myself what was going on. I found a good source for sea ice data, National Snow & Ice Data Center. After clicking through a few links, I found this data set in particular, Sea Ice Index (direct ftp link). It provided monthly mean extent and area data, so I downloaded that, put it into Excel, and plotted it. Below is the result of that work, a graph showing monthly averages by year.

Plotting it out like that really shows the misleading nature of the claim that arctic sea ice has recovered. There's a clear long term trend of decreasing ice extent. 2012 was an abnormally low year, and 2013 was an abnormally high year, but neither year was far off from that trend.

Here's another way of plotting the data. This is a simplistic average, summing the monthly averages and dividing by 12, but still shows the general trend.

Another way this is misleading is by expressing it as a percentage. Because of the long term trend, the minimums are getting lower and lower. The lower the minimums are, the higher percentage increase you'll get from any increase. A few years from now, if one year is only 1 million km², and the next was 2 million, I'm sure the denialists would shout that it was a 100% increase. Once we have an ice free summer, any amount of ice the next summer would be an infinite improvement percentage wise, but not much solace if the absolute coverage was still low.

In the course of my googling this, I came across a good article on SkepticalScience dealing with the claim in more depth than I have here, Arctic sea ice "recovers" to its 6th-lowest extent in millennia. I highly recommend you go read the entire article, but I couldn't resist stealing one of their animated images, illustrating how denialists view sea ice decline.

If you want to see another example of the denialist propaganda, here's an article from the Mail Online, And now it's global COOLING! Return of Arctic ice cap as it grows by 29% in a year. It contains similar claims to the Telegraph article quoted above.

It amazes me that intelligent, well educated individuals can fall for these types of propaganda, but the sad truth is that our world is warming, and we're already starting to face some of the effects of that change. Unless we do something about it soon, the future for us and our children will be much more painful and expensive than it needed to be.

Image Source: Wikimedia Commons