Arctic Ice Back to Normal

Since presenting a class on 'global warming' at Wichita State last week, I was challenged then and have since received emails questioning whether the Arctic ice is really recovering.  The answer is an emphatic yes as these graphs (from two different scientific sources) valid March 31, 2010 demonstrate. Click on graphic to enlarge, click on the colored link to see the raw data.

From the U.S. National Oceanic and Atmospheric Administration:

From the Japanese satellite visualization center:

Contrary to popular impression, the ice cover is growing (back to normal*) at the present time.

The ice has shrunk in summer primarily because of unusual wind currents (2007) and because of soot from Asia's industrialization being carried into the Arctic and darkening the snow and ice which causes it to melt much more quickly.  The ice recovers in winter (when it is dark 24 hours a day) because the soot factor doesn't apply in darkness.

It is possible that the weakening world economy caused less soot = less darkening last summer, but that is just a guess on my part.

In any case, the news is good.

* "Normal" here may be misleading and likely overstates the amount of ice that is "normal" in the Arctic. Why? Because this data set only goes back to 1979 when satellite data became available, which is at the nadir of world temperatures due to the cooling that occurred from about 1947 to 1977 (see graph below). We know that in the 50's there were times when the North Pole was free of ice.