Official 20 Set 3

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
置顶

Interglacial Periods

纠错
  • Q1
  • Q2
  • Q3
  • Q4
  • Q5
  • Q6
What is the lecture mainly about?
  • A. The effect of ice ages on the development of agriculture

  • B. A theory about a change in Earth’s climate cycle

  • C. Strategies to prevent Earth from entering another ice age

  • D. Some effects of industrialization on Earth’s atmosphere

显示答案 正确答案: B

我的笔记 编辑笔记

/
  • 原文
  • 译文
  • 查看听力原文

    关闭显示原文

    NARRATOR:Listen to part of a lecture in an environmental science class.

    MALE PROFESSOR:I'd like to take you back about 11,000 years ago when Earth, um, entered the latest, uh, interglacial period.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.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're in now, started about 11,000 years ago.

    Now, the typical pattern for an interglacial period-and we've studied several- is that the concentration of carbon dioxide and methane gas actually reaches it-its peak, that is, there's the most carbon dioxide and methane gas-greenhouse gases-in the atmosphere just after the beginning of the interglacial period.And then, for reasons which are not entirely clear, the concentration of greenhouse gases gradually goes down.Now, the climate continues to warm for a while because there is a lag effect, but gradually, as the concentration of greenhouse gases goes down,Earth starts to cool again and eventually you slip back into an ice age.

    Um, however, for the latest interglacial period, the one we're in now, this pattern did not hold.That is, the concentration of carbon dioxide and methane dipped a little bit after, uh, after peaking at the beginning, near the beginning of the interglacial period,but then it began to rise again.Um, what was different about this interglacial period than the other ones?Well, uh, one of the big differences is human activity.People began to raise crops and animals for food instead of hunting for them.This is the agricultural revolution, and it began to happen in the earliest stages about 11,000 years ago.

    Now scientists have tended to, uh, regard the, um, agricultural revolution as a beneficiary of the, uh, fortuitous shift in climate.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.When you grow crops or-and uh, pasture your animals, one of the things you do is you cut down the forests.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.

    Another, uh, gas associated with the spread of agriculture is methane.Methane forms in large concentrations above wetlands and, um, 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.

    So, um, agriculture, the spread of agriculture-you know we're talking over thousands of years- uh, but this could very well have had a profound effect on the composition of Earth's atmosphere.It's kind of ironic to think that, absent that effect, it may be that we would be heading into an ice age again.In fact, back in the 1970s, a lot of theorists were predicting that, you know, the climate would start to cool and we'd, we'd slowly enter into a new ice age.And then they were puzzled as to why it didn't seem to be happening.

    Um, now what are the implications for the future? Well, um, it's 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.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, uh, tends to put a lot of CO2 into the atmosphere.Uh, so we're entering into uncharted territory now, in terms of the amount of carbon dioxide, the concentrations of carbon dioxide that are now being put into the atmosphere as a result of industrialization and the use of fossil fuels.

  • 旁白:听一段环境科学课的讲座。

    教授:我希望能和同学们一起回顾一万一千年前的气候问题,当时,地球进入了最近的一次间冰期。间冰期是冰河时期之间的典型时期,这时气候暖和,冰原消退,直到气候重新变冷,另一个冰河世纪开始了。在过去的几百万年里,地球的主要气候特征实际上是冰河纪。但实际上它也有规律地解冻,而上一次解冻,就发生在一万一千年前。

    我们之前学习过的间冰期的几种气候模式,其中一种是大气中二氧化碳和甲烷含量达到峰值,即在间冰期的开端,大气中的温室气体(二氧化碳和甲烷)含量是最多的。之后,因为一些现在还不是特别明确的原因,温室气体的聚集逐渐下降。因为气候的变化有滞后效应,气候还会持续变暖一段时间,但是随着温室气体浓度的下降,地球的温度又重新开始下降,最终回到冰河时代。

    嗯,不过,最近的间冰期,我们现在所处的,这种模式不成立。也就是说,虽然在进入间冰期之后,甲烷和二氧化碳的含量自达到峰值以后有所下降,但之后它又开始上升了。嗯,这个间冰期比其他时期有什么不同?嗯,呃,最大的区别之一就是人类活动。不再依赖捕猎采集,人类开始种植庄稼,圈养牲畜来获取食物。这就是农业革命,它开始于11000年前的最初阶段。

    现在,科学家们倾向于,呃,把农业革命看作是气候的偶然转变的受益者。然而,一些新的气候学家提出了一些新的气候理论,也许人类对气候的影响早在农业革命开始的时候就已经开始了。当你种植庄稼或放牧牲畜时,你所做的第一件事就是砍伐森林。如果你砍伐森林,把树木作为燃料,并且没有换植其他的植株或者我们把砍得的木头烂在地里让别的植物没法生长,这样的结果是,很多碳元素会以二氧化碳的形式存在,并进入大气层。

    另一个,呃,与农业扩张有关的气体是甲烷。甲烷在湿地上空浓度较大。而且随着谷物种植面积的扩大,一大批人造湿地被制造出来,大量增加了进入大气层的甲烷含量,超过了以往的应有的水平。

    所以,嗯,农业的扩张,我们这里谈论的是成千上万年的农业扩展史,这很可能对地球大气层的成分有着深远的影响。如果没有这种效果,这是一种讽刺的想法,也许我们会再次进入冰河时代。事实上,早在20世纪70年代,许多理论家预言,你知道,气候会开始变冷,我们会慢慢进入一个新的冰河时代。然后他们感到困惑,为什么它似乎没有发生。

    嗯,现在对未来意味着什么?嗯,有点棘手。我的意思是,你可以说,这里有一个例子,嗯,人类活动,农业革命实际上是有益的。我们也许通过阻止冰河时代把气候变好了。但是,工业化当然大大增加了人类排放到大气中的二氧化碳的数量;化石燃料的燃烧,嗯,往往会把大量的二氧化碳排放到大气中。呃,我们现在进入了未知的领域,就二氧化碳的含量而言,工业革命和化石燃料大量消耗,使得大气层的二氧化碳含量高度聚集。

  • 官方解析
  • 网友贡献解析
  • 本题对应音频:
    1 感谢 不懂
    音频1
    解析

    题型分类:主旨题

    音频定位: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 dipped1 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. Um ... What was different about this interglacial period than the other ones?

    选项分析:教授的主题是提出了个理论,人类的活动使得climate cycle发生变化。

    标签

题目讨论

如果对题目有疑问,欢迎来提出你的问题,热心的小伙伴会帮你解答。

如何吃透这篇文章?

Interglacial Periods

0人精听过

预计练习时间:16min19s

马上精听本文

最新提问