The yellow outline shows the median sea ice extent observed by satellite sensors in September and March from 1979-2000. "extent" is the total area with an iceconcentration of at least 15 percent.
黄色勾勒出由卫星传感器自1979——2000年所观测到得海冰面积的在九月和三月中间范围。
2
Gradually as the concentration of greenhouse gases goes down, Earth starts to cool again, and eventually you slip back into an Ice Age.
随着温室气体浓度的下降，地球开始再次变冷，最终又将回到冰河时代。
3
The formation of sea ice causes the concentration of salt in surface waters to increase; less sea ice would mean a smaller increase in the concentration of salt.