From 1979 to 2017, the extent of the Arctic sea ice decreased significantly, whereas that of the Antarctic sea ice generally showed an upward trend. However, the range of the Antarctic sea ice was abnormally small in 2017, with a minimum value in March and the second smallest value in September since the start of satellite observation records. In addition, the global sea level has been rising consecutively for six years. In 2016, the global average sea level reached a new height, approximately 82 mm higher than when satellite recording began in 1993. Over the past 20 years, the sea level has risen at an average rate of approximately 3.4 mm per year, with the highest increases being observed in the Western Pacific and Indian oceans.