A recent result from the Climate Change Initiative (CCI) #SeaIce project I happen to co-lead for the European #Space Agency.
Stefan Kern (University of Hamburg) investigated the accuracy of #SeaIce Concentration data obtained from an old US satellite: Nimbus-5 (1972 - 1977). This gives some confidence in sea-ice data from before most #ClimateData starts (1979).
You can read a bit more about the ESMR data itself here:
https://climate.esa.int/en/news-events/Update-of-the-Nimbus-5-ESMR-sea-ice-concentration-dataset/
