8 September 2011

That time of year again (part 2)

A few days ago I posted a little graph from the National Snow and Ice Data Centre in the US, plotting the Arctic summer sea ice melt as we head toward toward the summer minimum, usually sometime around mid September. It’s tracking tantalisingly close to the 2007 record low.

In truth looking at ice extent for an individual year, while an opportunity for some bet making entertainment, isn’t terribly meaningful. If we do get a new record it could be down to a number of factors, Global Warming will be just one of them. Naturally variable weather can have a lot to do with it too. (The National Centre for Atmospheric Research crunched the data and estimated that between 1979 and 2005 influence is shared about 50:50 for warming vs other factors)

What is significant is the long term trend.

Natural variability can play either way so, while it can have a big effect on individual years, over time it evens out and has little bearing on long term trends. The trend is the warming signal.

So come on Bob, Ruth, Claire and Jo - what say you? I’m going with no new record for Arctic Summer Ice Extent minimum for this year (I’ve no special info, it could still go either way). Losers attend the Barn Dance in fancy dress.

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