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Narrator:Listen to part of a lecture in an environmental science class.
獨白:聽下面一段環境科學課堂上的講解。
Professor:Basically, a cloud either contributes to the cooling of Earth's surface or to its heating.
教授:基本上，云的作用是降低或升高地球表面的溫度。
Earth's climate system is constantly trying to strike a balance between the cooling and warming effects of clouds.
地球天氣系統一直試圖在云的降溫和保溫作用中尋求一個平衡。
It's very close, but overall the cumulative effects of cloud are to cool Earth rather than heat it.
這十分相近，但是總體上來說，云的累積作用是降低地球的溫度而不是加熱。
And this balance between the amount of solar radiation, energy from the Sun, that's absorbed by Earth, and the amount that's reflected back into space.
這個平衡是指太陽的輻射量，也就是被地球吸收太陽能量與反射回宇宙中的能量之間的平衡。
We call this Earth's radiation budget.
我們稱之為地球輻射收支。
And one way we keep track of the radiation budget is by looking at the albedo of the different surfaces on the planet.
我們觀察輻射收支的方法之一就是通過觀測地球不同表面的反照率。
A surface's albedo is the percentage of incoming solar energy, sunlight, that's reflected off that surface back into space.
表面反照率是指接受的太陽能量、陽光與反射回空間中的能量的比率。
Oceans have a low albedo, because they reflect very little energy.
海洋的反照率很低，因為反射的能量很小。
Most of the solar energy that reaches the ocean gets absorbed and heats the water.
大部分到達海洋的太陽能量都被吸收并使海水增溫。
Um... rainforests also have low albedos.
雨林也具有低反照率。
Well, by contrast, deserts and areas covered by ice and snow, these places have high albedos.
相反的，沙漠地區或被冰雪覆蓋的地區具有高反照率。
And clouds, in general, cloud also have high albedos.
一般來說，云具有高反照率。
That means that a large percentage of the solar energy clouds receive is reflected into space.
這就是說，云接受的大部分太陽能量都被發射回太空了。
OK. Now, when we say that clouds have a high albedo.
好的。當我們說云具有高反照率，
We are talking about the effect of all the clouds on earth averaged together.
我們說的是所有類型的云的平均反照率。
But different types of clouds have different reflective properties, they have different albedos.
但是不同種類的云有不同的反射性，也就有不同的反照率。
Student:So which type of clouds cools Earth? And which type heat it?
學生:那么什么類型的云為地球降溫？什么類型的又使地球升溫呢？
Professor:Well, high thin clouds contribute to heating while low thick clouds cool Earth.
教授:高空的薄云層使地球升溫，而低空的厚云層為地球降溫。
High thin clouds are very transparent to solar radiation, like, uh, clear air.
太陽輻射可以輕易地通過高空薄云層，就像通過空氣一樣。
So they mostly transmit incoming solar energy down to Earth.
所以大部分的太陽能量都會傳輸到地面。
There's not much reflection going at all.
薄云層沒有多少反射作用。
At the same time, these clouds trap in some of Earth's heat.
同時，這些云層還會留住一些地球的熱量。
Because of the trapped heat, these clouds have an overall heating effect.
由于這些截留的能量，這類云總體上有升溫作用。
Student:Oh. OK. Since low thick clouds are not transparent to radiation...
學生:哦，這樣。由于輻射無法透過低空厚云層。
Professor:Exactly. They block most of the solar energy so it never reaches Earth's surface.
教授:沒錯。他們阻擋了大部分的太陽能量，所以太陽能量無法到達地球表面。
They reflect much of it back out into space.
大部分的太陽能量被發射到太空中。
Student:So that's how they contribute to cooling?
學生:這就是為什么他們使地球降溫？
Professor:Yep. And as I said earlier, this cooling effect predominates.
教授:是的，之前我說過，這種降溫作用占主導地位。
Now, what if there was a process that could control the type of clouds that form?
現在想想，要是有一種方法可以控制這種云的形成？
Student:Are you talking about controlling the weather?
學生:您是說控制天氣？
Professor:Well, I am not sure I would go that far.
教授:我不確定能夠辦得到。
But we recently noticed an increase in cloud cover over an area of the ocean waters around Antarctica.
但是，近期我們注意到在南極洲附近的海水上空的云層覆蓋量有所增加。
An increased area of low thick clouds, the type that reflects a lare portion of solar energy back to space and cools the Earth.
是低空厚云層的增加，可以將大部分太陽能量反射回太空的云層。
Well, the reason for this increased cloud cover, it turns out, is the exceptionally large amount of microscopic marine plants.
造成云蓋增加的原因，是大量的顯微鏡可見的海洋植物。
Well, the current hypothesis is that these microorganisms produce a chemical, dimetho sulfide that interacts with the oxygen in the air, creating conditions that lead to the formation of the low thick clouds we observed.
近期的一個假設是，這種微生物產生一種化學物質，即硫化物，它與空氣中的氧相互作用，創造了一個適合我們所觀察到的低空后云層產生的環境。
Well, that's true.
這個假設是正確的。
It could have huge implications.
它有著巨大的啟發。
So, maybe we are talking about controlling the weather.
所以我們很有可能控制天氣。
Perhaps, if the microorganisms near Antarctica really are responsible, perhaps we can accelerate the process somehow.
若果南極洲的微生物真的是引起云層增加的原因，或許我們能夠加快這個進程。
