The 1990 IPCC Report showed a two million km² increase in Arctic ice during the five years prior to 1979. This was based on Nimbus satellite data.
For some reason, Wikipedia seem to have missed this huge gain in ice.
File:Seaice-1870-part-2009.png – Wikipedia, the free encyclopedia
Just another reason to ignore Wikipedia. It’s part of the propaganda machine.
What would be interesting is to see where the ‘average’ line would be on the NSIDC, Nansen and JAXA graphs, if 1975 to 1979 were included in the average.