Arctic sea ice minimum extent, 2005. The extent of the sea ice varies over the course of a year, being largest in winter and smallest in summer. Comparing the maxima and minima over several years allows trends in the extent of the sea ice to be followed. Both the minimum and maximum extent of Arctic sea ice have reduced greatly since the middle of the 20th century, providing powerful evidence for global warming due to carbon emissions. A similar image showing the minimum extent of ice in 1979 is E205/090. E205/091 shows the minimum extent in 2003. Data from the Special Sensor Microwave Imager (SSMI) on a Defense Meteorological Support Program (DMSP) satellite.