“1979 and 1982”
So that somewhat confirms the theory that as Arctic extent decreases, Antarctic extent increases—and vice versa. Since the AMO, PDO, and AO periodicity have not been convincingly long enough to fully cycle through each, those natural phenomenon could explain most if not all of the decline in Arctic extent. We’ll have to wait and see another 10-20 years to determine whether or not Arctic extent returns to historical levels or if there’s truly something else going on.
sunshine hours 
Which other two years besides 2016 are lower than this year?
2010 and 2012
I’m sorry, I should have been more specific. I meant for the Antarctic.
1979 and 1982.
“1979 and 1982”
So that somewhat confirms the theory that as Arctic extent decreases, Antarctic extent increases—and vice versa. Since the AMO, PDO, and AO periodicity have not been convincingly long enough to fully cycle through each, those natural phenomenon could explain most if not all of the decline in Arctic extent. We’ll have to wait and see another 10-20 years to determine whether or not Arctic extent returns to historical levels or if there’s truly something else going on.