In recent decades, sea ice in the Arctic Ocean has been melting faster than it re-freezes in winter.

The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report states that greenhouse gas forcing is predominantly responsible for the decline in Arctic sea ice extent.

The IPCC Fifth Assessment Report concluded, with high confidence, that sea ice will continue to decrease in extent, and that there is robust evidence for the downward trend in Arctic summer sea ice extent since 1979.‏⁴ It has been established that the region is at its warmest for at least 4,000 years‏⁵ and the Arctic-wide melt season has lengthened at a rate of 5 days per decade (from 1979 to 2013)