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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的課程。
I'd like to take you back about 11 thousand years ago when Earth entered the latest interglacial period.
教授:我希望能和同學們一起回顧一萬一千年前的氣候問題，當時，地球進入了最近的一次間冰期。
Interglacial periods are, typically periods of time between Ice Ages, when the climate warms, and the glacial ice retreats for a time, before things cool off again and another Ice Age begins.
所謂間冰期，指的是兩次冰河世紀的相間的時間段。當氣候暖和了之后一段時間，冰原就會消退，直到氣候重新變冷，另一次冰河世紀開始，而在此之間就是所謂的間冰期。
And for over the past several million years, Earth's sort of default climate has actually been Ice Age, but we have experienced periodic regular thaws, and the last one, the one we are in now, started about 11 thousand years ago.
在過去的幾百萬年里，地球的主要氣候特征實際上是冰河紀，但實際上它也有規律地解凍，而上一次解凍，就發生在一萬一千年前。
Now, the typical pattern for an interglacial period, and we have studied several, is that the concentration of carbon dioxide and methane gas actually reaches it... its peak, that is, there is the most carbon dioxide and methane gas, uh, greenhouse gases in the atmosphere just after the Beginning of the interglacial period.
我們之前學習過的間冰期的幾種氣候模式，其中一種是大氣中二氧化碳和甲烷含量達到峰值，即在間冰期的開端，大氣中的溫室氣體含量是最多的。
And then, for reasons which are not entirely clear, the concentration of greenhouse gases gradually goes down.
之后，因為一些現在還不是特別明確的原因，溫室氣體的聚集逐漸下降。
Now, the climate continues to warm for a while because there is a lag effect.
那么，為什么氣候還一直變得更加暖和呢？是因為，氣候的變化相對于溫室氣體含量的變化存在一定的延遲。
But uh, gradually as the concentration of greenhouse gases goes down, Earth starts to cool again, and eventually you slip back into an Ice Age.
但是，嗯，隨著溫室氣體的含量降到一定水平，地球的溫度又重新開始下降，最終回到冰凍狀態。
Um, however, for the latest interglacial period, the one we are in now, this pattern did not hold, that is, the concentration of carbon dioxide and methane dipped a little bit after, uh, uh, after peaking at the beginning, near the beginning of the interglacial period, but then it began to rise again.
嗯，但是，在最后一次間冰期之后，即我們現在所處的時代里，這種模式就不適應了。雖然在進入間冰期之后，甲烷和二氧化碳的含量自達到峰值以后有所下降，但之后它又開始上升了。
Um ... What was different about this interglacial period than the other ones?
嗯，這一次間冰期和之前的間冰期，有什么不同呢？
Well, one of the big differences is human activity.
這次間冰期和之前的相比，最重要的不同，在于人類的活動。
People began to raise crops and animals for food instead of hunting for them.
人類種植莊稼，圈養牲畜來獲取食物，而不是獵取它們。
This is the agricultural revolution.
這是農業的重大革命。
And it began to happen in the earliest stages about 11 thousand years ago.
而且，這項革命發生在一萬一千年前的早期。
Now, scientists have tended to regard ... the ... uh ... agricultural revolution as a beneficiary of the ... uh ... fortuitous shift in climate.
現在，科學家們都傾向于認為農業革命是，嗯，受益于偶然性的氣候變化的。
However, some new theories of climate, new theorists of climate have proposed that perhaps humanity was having an effect on the climate as far back as the beginnings of the agricultural revolution.
但是，一些新的氣候理論學家提出了許多新的氣候學理論，提出，自從此次間冰期的開始后的農業革命開始，人類的活動一直都在影響自然氣候。
When you grow crops and uh, pasture your animals, one of the things you do is you cut down the forests.
當我們種植農作物，喂養牲口時要做的第一件事情就是砍伐森林。
If you cut down the forests, when you burn the trees for fuel and don't replace them with other trees, or when you just leave them to rot and don't allow other trees to grow, you end up with a lot more carbon in the form of carbon dioxide getting into the atmosphere.
當森林被伐之后，人類就把木頭作為燃料，并且沒有換植其他的植株；或者我們把砍得的木頭爛在地里讓別的植物沒法生長，這樣的結果是，很多碳元素會以二氧化碳的形式存在，并進入大氣層。
Um ... another gas associated with the spread of agriculture is methane.
另一種隨著農業擴張而過量產生的其他是甲烷。
Methane forms in large concentration above wetlands, and as it turns out, the cultivation of certain grains creates vast areas of artificial wetlands, and probably drastically increases the amount of methane getting into the atmosphere, over and above what would be there.
甲烷在沼澤上大批形成，而且，隨著谷物種植面積的擴大，一大批人造濕地被制造出來，大量增加了進入大氣層的甲烷含量，超過了以往的應有的水平。
So, um... agriculture, the ... the spread of agriculture, you know we are talking over thousands of Years, um... but this could very well had a profound effect on the composition of Earth's atmosphere.
總之，嗯，農業的擴張，我們這里談論的是成千上萬年的農業擴展史，而且這段時間內的農業擴張對地球大氣層的成分有著分廠深遠的影響。
It's kind of ironic to think that absent that effect, it maybe that we would be heading into an Ice Age again.
有的科學家忽略了這種影響的存在，認為我們將再次緩慢進入冰河世紀。
In fact, back in the 1970s, a lot of theorists were predicting that, you know, the climate would start to cool and we'd slowly enter into the new Ice Age.
實際上，回溯到 1970 年代，許多環境理論專家就預測過氣候的再次變冷，世界再次重新進入冰河世紀的發生。
And then they were puzzled as to why it didn't seem to be happening. Umm... now, what are the implications for the future?
之后，他們被事實弄得很困惑:為什么地球還沒有變冷？嗯，現在，氣候變化對我們的未來意味著什么呢？
Well, um... it is a little tricky. I mean, you could say, well, here is an example of ... um ... human activity, the agricultural revolution which actually was beneficial; we altered the climate for the better, perhaps, by preventing an Ice Age.
嗯，這其實非常的微妙。我的意思是，人們既可以認為，這個間冰期的人類活動，農業革命是有益的；我們可以認為，這種溫室氣體的增加，是一種好的現象，因為它推遲了進入冰河世紀的時間。
But then industrialization, of course, has drastically increased the amount of carbon dioxide that humans are putting into the atmosphere, the burning of fossil fuels tends to put a lot of CO2 into the atmosphere.Um ...so we are entering into uncharted territory now, in terms of the amount of carbon dioxide and the concentration of carbon dioxide that are now being put into atmosphere as a result of industrialization and the use of fossil fuels.
但是，其后的工業革命，大大增加了人類向空氣中注入二氧化碳的總量；化石燃料的消耗往大氣中灌注了海量的二氧化碳，總之，工業革命的到來使得化石燃料大量消耗，大氣層的二氧化碳含量高度聚集。
