Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 230

Figure 10.1
Northern Hemisphere September sea ice extent as simulated by six models using the IPCC A1B emission
scenario. The results show the chaotic nature of natural variability and the long-term trend (decline) due
to anthropogenic forcing.
Why is the extent of summer sea ice receding? The answer is quite simple. Our world is
getting warmer. In the words of the fifth assessment (AR5) of the Intergovernmental Panel
on Climate Change (IPCC): “Warming of the climate system is unequivocal, and since the
1950s, many of the observed changes are unprecedented over decades to millennia. The
atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea
level has risen and the concentrations of greenhouse gases (GHGs) have increased.” 1 The
same assessment reported: “Each of the last three decades has been successively warmer at
the earth's surface than at any preceding decade since 1850. In the Northern Hemisphere,
1983-2012 was likely the warmest 30-year period of the last 1400 years (medium confid-