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These two qualities, floating and reflecting,
漂浮和反射這兩種性質(zhì)
make ice uniquely powerful on Earth.
令冰塊在地球上具有獨特的能量
Ice turns these polar regions into two giant reflectors,
冰將兩級區(qū)域變成兩個巨大的反光鏡
and they don't just reflect light but heat.
不僅反射光線，還有熱量
Land and sea are dark so they absorb the Sun's warmth,
陸地和海洋是黑暗的，它們吸收太陽的熱量
but ice reflects it straight back out to space.
但是冰將熱量反射回空間
It's called the albedo effect.
這被稱為反照率作用
Filmed for a year from a satellite above the North Pole,
衛(wèi)星從北極上方拍攝一年
you can see how the Arctic sea ice grows and shrinks with the seasons.
便能看到北極海洋的冰層會按季節(jié)擴大和縮小
This changes the amount of energy absorbed by the Earth,
這個變化將改變地球吸收的能量總量
and this in turn can influence the climate right across the planet.
也將影響整個行星的氣候
So the amount of fee cover can have a dramatic effect on climate worldwide,
足以影響星球上的一切冰層可以引起氣候的巨變
one that may even have affected the path of human evolution.
甚至影響人類自己的進化
Fossils found all over Africa show how in the last three million years
非洲東部出土的化石顯示過去三百萬年里
there appear to have been two great evolutionary leaps forward.
那里人類的進化經(jīng)歷了兩次巨大飛躍
The first was the appearance of an ape man with a larger brain.
首先是猿人的出現(xiàn)他們有著很大的大腦
