漂浮和反射这两种性质
make ice uniquely powerful on Earth.
令冰块在地球上具有独特的能量
Ice turns these polar regions into two giantreflectors,
冰将两级区域变成两个巨大的反光镜
and they don't justreflect light but heat.
不仅反射光线，还有热量
Land and sea are dark so they absorb the Sun's warmth,
陆地和海洋是黑暗的，它们吸收太阳的热量
but ice reflects it straight back out to space.
但是冰将热量反射回空间
It's called the albedo effect.
这被称为反照率作用
Filmed for a year from a satellite above the North Pole,
卫星从北极上方拍摄一年
you can see how the Arctic sea ice grows and shrinks with the seasons.
便能看到北极海洋的冰层会按季节扩大和缩小
This changes the amount of energy absorbed by the Earth,
这个变化将改变地球吸收的能量总量
and this in turn can influence the climate right across the planet.
也将影响整个行星的气候
So the amount of fee cover can have a dramatic effect on climate worldwide,
足以影响星球上的一切冰层可以引起气候的巨变
one that may even have affected the path of human evolution.
甚至影响人类自己的进化
Fossils found all over Africa show how in the last three million years
非洲东部出土的化石显示过去三百万年里
there appear to have been two great evolutionary leaps forward.
那里人类的进化经历了两次巨大飞跃
The first was the appearance of an ape man with a larger brain.
首先是猿人的出现他们有着很大的大脑
