FIGURE 64.1 The melting polar ice cap. Because northern latitudes have experienced the greatest amount of global warming, the extent of the ice cap near the North Pole has been declining over the past 3 decades. The polar ice cap reaches its minimum late in the summer of each year, so we can look for a trend by examining the extent of ice each September. From 1979 to 2013, the polar ice has declined an average of 14 percent per decade.
(Data from http://nsidc.org/arcticseaicenews/2013/10/)