Another source of observational data on the effects of recent warming

The Arctic Sea-ice Monitor tracks the extent of sea ice over the Arctic, and has for a long time posted a wonderful graph that shows sea ice extent over each month in a given year.  In the new graph now appearing on their site (reposted below) they show the monthly averages for the 1980s, 1990s, and 2000s, and each decade shows significantly declining sea ice extent in the critical months of August, September, and October.  This graph is yet another fingerprint showing a warming world, based on actual measurements (not climate models).

And the big story right now is the 2012 line, which has been close to the lowest sea-ice extent ever recorded for the past few months.  We’ll know soon if 2012 will beat 2007 for minimum sea ice extent in September.

For those who really want to dig into the details, Real Climate has the story with lots of links and context.

Addendum, August 14, 2012:  Two commenters noted correctly that the volume of sea ice is also important, not just the extent.  The Polar Science Center gives those data, summarized in the graph just below.

Caption:  Total Arctic sea ice volume from PIOMAS showing the volume of the mean annual cycle, the current year, 2010 (the year of previous September volume minimum), and 2007 (the year of minimum sea ice extent in September). Shaded areas indicate one and two standard deviations from the mean.

This graph indicates that while 2007 and 2012 may be comparable in terms of sea ice extent, the later year has much lower sea ice volume, which is another indication of the warming trend we’ve seen over the past several decades.

For more details, check out the Arctic Sea Ice News and Analysis page.  And  see also this graph posted on Brave New Climate, which shows exponential decay for the minimum sea ice volume.  This is not a pretty picture!

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