Sea ice can be described as frozen seawater floating on the surface of the polar oceans. It does not include icebergs or ice shelves, as these are originating from glaciers, rather than sea water. Sea ice becomes thickest and most widespread over the respective winter months in each hemisphere, covering the oceans around the Arctic and Antarctic with millions of square kilometres of ice. It melts when the seasons change, but in the Arctic large areas remain covered all year around, while Antarctic sea ice melts away over the summer in the southern hemisphere.
Recent figures released by the NASA as well as the British Met Office and NOAA confirm that 2015 was the hottest year ever recorded. In addition, the period of the past five years was also the warmest in recent times. The following map animation visualises a data series by NASA’s Goddard Institute for Space Studies (GISS) that depicts “how much various regions of the world have warmed or cooled when compared with a base period of 1951-1980. They show temperature anomalies, or changes, not absolute temperature. (The global mean surface air temperature for that period was estimated to be 14°C or 57°F.)” It uses an equal population project in form of a gridded cartogram so that the underlying temperature anomalies can seen in relation to the global population distribution: