What is the reason behind the fact that “[Arctic] sea ice area [is] approaching the edge of normal standard deviation“?
It’s because October 2008 is set to break all records in the daily rate of increase in sea ice extent in the Arctic, that’s why.
Just look at the graph below, extracted from the values available at the IARC-JAXA website.
(The Y values are the daily rates of change in sea ice extent in the Arctic, averaged across each month. Note that for October I have only computed and plotted the rates between the 1st and the 23rd day of the month).
(a) The October 2008 average daily rate so far is the largest overall, both in actual value (around 122,400 sq km of increase per day, previous record 100,500 in 2005) and in absolute terms (the overall minimum is around 94,000 sq km of decrease per day, in July 2007)
(b) If confirmed in a week’s time, the above will become the fifth record set in 2008:
largest January daily increase rate (44,000, previous record 39.800 in 2003)
largest February daily increase rate (27.500, previous record 25,400 in 2005)
largest May daily decrease rate (47,100, previous record 46,000 in 2005)
largest August daily decrease rate (66,800, previous record in 62,600 in 2004)
(c) Compared to 2007, the current year 2008 has so far shown
larger daily rates of increase in January (44,000 vs 35,400), February (27,500 vs 12,100), September (8,800 vs -600) and October (122,400 vs 93,500)
larger daily rates of decrease in April (39,800 vs 27,100), May (47,100 vs 44,200) and August (66,800 vs 55,400)
smaller daily rates of decrease in March (11,900 vs 12,200), June (57,900 vs 63,000) and July (78,800 vs 94,000)
Let’s see what happens during the upcoming week.
Past values suggest that the final average daily rate of increase for October may be slightly less than today’s. Still, as the current rate is some 20% larger than the previous record in October 2005, it would surprise nobody if October 2008 will remain the month with the largest value ever recorded by JAXA.
ps Who knows what NASA will have to say?