By Phil Plait
28 May 2013
(Slate) – It’s no surprise to regular readers I am quite concerned about climate change. My concern on this issue is two-fold: one consists of the actual global consequences of the reality of global warming, and the other is the blatant manipulation of that reality by those who would deny it.
These two issues overlap mightily when it comes to Arctic sea ice. The ice around the North Pole is going away, and it’s doing so with alarming rapidity. I don’t mean the yearly cycle of melt in the summer and freeze in the winter, though that plays into this; I mean the long-term trend of declining amounts of ice. There are two ways to categorize the amount of ice: by measuring the extent (essentially the area of the ocean covered by ice, though in detail it’s a little more complicated) or using volume, which includes the thickness of the ice. Either way, though, the ice is dwindling away. That is a fact.
Of course, facts are malleable things when it comes to the deniosphere. One popular denier claim is that Arctic sea ice extent is higher in recent years than it was in 1989, therefore claims of it melting away are false.
This is so blatantly wrong that it’s hard to believe anyone could make that claim with a straight face. But make it they do, like Lawrence Soloman did in (surprise!) an OpEd in the Financial Post (which, like the Wall Street Journal, is a refuge for denialist claims). Soloman’s silliness is taken apart easily by Tamino on his blog. Harrison Schmitt has made this claim as well. It’s simple cherry picking your data, and a huge no-no when it comes to real science.
When you look at the average, the trend in the ice, it goes down, down, down. Over time, there’s less.
How much less? I was curious about this recently, because most of the graphs I see deal with what scientists call “anomalies”, that is, departures from average. If people average 180 centimeters tall, and you are 182 cm in height, your “height anomaly” is +2 cm. If you were 173 cm tall your height anomaly is -7 cm. Simple, and useful when dealing with some physical effects, but sometimes the emotional impact is lost. If you hear someone has a height anomaly of +15 cm you’d think that was interesting, but if you met them in person you’d see that means they’re really tall.
The same with sea ice. Graphs show us that sea ice is declining over time, but it’s shown as a percentage, or a deviation from some past period. That’s good to give you a grasp of the situation, but doesn’t tell you how much actual ice is left.
So what’s the real loss of ice we’re experience every year?
The answer is: a lot. A whole lot. Even after seeing the numbers, I was taken aback by this graph which shows sea ice extent plotted over time. [more]