Arctic and Baltic sea ice
- The extent and volume of the Arctic Sea ice has declined rapidly since global data became available in 1980, especially in summer. Record low sea ice cover in September 2007, 2011 and 2012 was roughly half the size of the normal minimum extent in the 1980s. In September 2013 ice cover was well below the average for 1981-2010.
- Over the period 1979–2013, the Arctic has lost on average 43 000 km2 of sea ice per year in winter and 95 000 km2 per year at the end of summer. The decline in summer sea ice appears to have accelerated since 1999.
- The maximum sea ice extent in the Baltic Sea has been decreasing most of the time since about 1800. The decrease appears to have accelerated since the 1980s but the large interannual variability prohibits a clear assessment as to whether this increase is statistically significant.
- Arctic Sea ice is projected to continue to shrink and thin all year round. For high greenhouse gas emissions, a nearly ice-free Arctic Ocean in September is likely before mid-century. There will still be substantial ice in winter.
- Baltic Sea ice, in particular the extent of the maximal cover, is projected to continue to shrink.