Arctic sea ice minimum has come and gone. What does it mean?

Summer is gone, and with it the annual sea ice melt. This year was, depending on your point of view, either the second straight year of increasing sea ice or the third lowest extent of sea ice known. Both are true. So which one’s more important? NSIDC obsesses over the second part of that. But I disagree.

The rebound is far more important than NSIDC’s lead of it being the third lowest extent. This is because the rebound demonstrates just how little we know of climate and how it works. Allow me to explain.

Two years ago, when we saw the dramatic loss of sea ice, we were inundated with warnings that the arctic was in a downward death spiral. See, the loss of ice meant a loss of whiteness, which means the arctic would absorb more heat, which means that more ice would melt, etc., etc. And then winter of 2007 came, and arctic ice immediately refroze and jumped back up to where it was a few years ago. But that was irrelevent, we were told, because it was all new ice. Because there was all new ice, it would melt faster the following year. Which would mean more new ice, which would mean a more rapid meltoff the following year, etc., etc.

2008 came. 2008 went. While the ice melt was extreme, it wasn’t as bad as 2007. Clearly, it wasn’t a death spiral. And then it, too, rebounded to historical levels during the refreezing. But that’s ok. Because now, most of the ice was less than 2 years old. Which means it will also melt really fast, meaning the arctic is still doomed!

And now 2009 has come and gone. And the melt is improved yet again. I wonder if 2010 is doomed because the ice is all less than 3 years old…

Don’t believe me? Here’s a list of expert predictions made in July of this year (H/T: Watt’s Up With That). One model predicted minimum extent would be less than 2007, seven predicted it would be between 2007-2008 levels, three predicted it would be just above 2008 levels, and three substantially above 2008 levels. In the end, every single model lowballed the estimate. Every. Last. One.

Clearly we don’t know enough about arctic sea ice to be able to make predictions 2 month in advance, much less to tell us anything important about climate change.

We know now that 2007’s rapid meltdown was due to shifting ocean currents and not global warming. 2008 and 2009 are likely just returning the ice levels back to its initial level. The fact that it’s taking so long during the summers (remember, during winter it’s already back to normal) is probably due to the young ice issue I alluded to. However, instead of the feedback leading to a death spiral, it just means there’s a slow recovery. Within a year or two, barring any more weird currents that take away a huge chunk of ice, we should be back to our normal, slightly negative trend of losing ice every year.

But that trend only shows ~25-30 years or so of good data. So what do we actually know about long term trends? What information can this actually tell us?

Pretty much nothing, actually. Without any long term trends, we don’t know if sea ice extent is cyclical, how quickly it can rebound, or if this is part of a longer trend and not necessarily related to warming (note that our data picks up as soon as global warming started again, so we have no baseline to know what sea ice will do during a few decades of cooling). So why does it get so much press?

Because it’s dramatic. 2007 was dramatic. Antarctic ice is boring. Greenland ice is boring. Temperature trends are boring. But concerns that Santa’s workshop might melt away? *GASP*


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