The multi-channel satellite passive-microwave record of Earth's sea ice coverage, extending back to the late 1970s, has long revealed declining sea ice coverage in the Arctic but through 2015 revealed an overall increase rather than decrease in Antarctic sea ice coverage. Following major decreases in Antarctic sea ice since 2015, the 42-year 1979–2020 satellite dataset now shows recent losses in sea ice coverage in both hemispheres, and this is convincingly demonstrated by the enumeration of monthly and yearly record high and record low sea ice extents experienced over the course of the 42 years. In fact, one of the most convincing statistics on the declining Arctic sea ice cover is the fact that since 1986 the Arctic has not experienced a single monthly record high sea ice extent in any month but has experienced 93 monthly record lows. In contrast, all 12 calendar months have their 42-year Antarctic monthly record high sea ice extents in the period 2007–2015, while 8 of the 12 calendar months have had Antarctic record lows since 2015. Globally, every calendar month has registered a new monthly record low within the past 5 years. These results are complemented (and somewhat tempered) by quantification of the range of monthly and yearly sea ice extent values over the 42 years. For instance, although the Arctic's lowest September monthly average sea ice extent (in 2012) is 53% lower than its highest September monthly average sea ice extent (in 1980), the other months have far smaller percent differences between their lowest and highest Arctic values. For yearly average sea ice extents, the Arctic's lowest value (in 2020) is 18% lower than its highest value (in 1982), the Antarctic's lowest value (in 2017) is 16% lower than its highest value (in 2014), and the global lowest value (in 2019) is only 12% lower than its highest value (in 1982).

地球海冰覆盖率的多通道卫星无源微波记录可以追溯到 1970 年代后期，长期以来一直揭示北极海冰覆盖率下降，但到 2015 年，南极海冰覆盖率总体增加而不是减少。自 2015 年以来南极海冰大幅减少后，1979-2020 年 42 年的卫星数据集现在显示两个半球的海冰覆盖率最近都在下降，这通过每月和每年创纪录的高海冰和创纪录的低海冰的枚举令人信服地证明在 42 年的过程中所经历的范围。事实上，关于北极海冰覆盖率下降的最有说服力的统计数据之一是，自 1986 年以来，北极没有任何一个月经历过一次创纪录的高海冰面积，而是经历了 93 个月度创纪录的低海冰面积。相比之下，2007 年至 2015 年期间，所有 12 个日历月的南极海冰面积均创下 42 年历史新高，而 12 个日历月中有 8 个日历月的海冰面积自 2015 年以来创下了南极历史新低。月度创近 5 年新低。通过量化 42 年来每月和每年海冰范围值的范围，对这些结果进行了补充（并且在某种程度上有所缓和）。例如，尽管北极 9 月最低月平均海冰范围（2012 年）比 9 月最高月平均海冰范围（1980 年）低 53%，但其他月份的最低和最高北极值之间的百分比差异要小得多. 对于年平均海冰范围，北极的最低值（2020 年）比其最高值（1982 年）低 18%，