A 30-year satellite record of sea ice extents derived mostly from satellite microwave radiometer observations reveals that the Arctic sea ice extent decreased by 0.30+0.03 x 106 km2 per decade from 1972 through 2002, but decreased by 0.36+0.05 x 106 km2 per decade from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast to the Arctic, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased, with an overall 30-year trend of -0.15 + 0.08 x 106 km2/10yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent observed in the early 1970’s. The results have been submitted for publication in Science and GRL.