『新东方在线托福听力』为托福考生准备了ETS托福TPO/Official 40 Lec 3听力练习：What is the main purpose of the lecture？原文题目答案解析，TPO/Official 40 Lec 3听力原文范文音频翻译。

托福TPO/Official 40 Lec 3听力原文What is the main purpose of the lecture？【新东方在线】

旁白：下面请听一段环境科学讲座的片段。

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

教授：接下来的几周，我们将集中在碳元素上以及它在“温室效应”中的作用。

Professor: Now, over the next few weeks, we're gonna focus on carbon and its role in what's known as the "greenhouse effect".

大家都知道温室效应是什么，对吗？

学生：温室效应是当温室气体在地球大气层里，它们就像温室的玻璃一样。

Student: The greenhouse effect is when gases in Earth's atmosphere act like the glass in a greenhouse or a hothouse.

不让热量消散，使得地球温度上升。

They trap in heat which warms up the earth.

Student: Um, water vapor? Carbon dioxide?

我们最近听说很多有关碳的事，不是么？

We hear a lot about carbon these days, no?

Carbon emissions, carbon burning, leaving a carbon footprint.

所以我们很容易推断出任何形式的碳燃烧必定是个坏事。

So it'd be easy to assume that any form of carbon burning is necessarily a bad thing.

但是事实是：并不是那么简单。

But the fact is: it's not quite that simple.

所以今天我们主要来看下那些好的，坏的，不是那么坏的，潜在是有益的碳燃烧的区别。

So we're gonna focus today on the difference between good, bad, and well, the, not so bad, the potentially okay carbon burning.

我们每个人都亲自参与其中，因为燃烧碳是生命的基础。

Well, we all have a personal stake in this because burning carbon is the basis of life.

如果我们不燃烧碳那么人类就不会存在。

We wouldn't be here if we ourselves weren't burning carbon.

基本上，所有的生物都依赖燃烧碳而存活。

Basically, all living things burn carbon to survive.

通常这是发生在生物的细胞阶段，燃烧的是以糖，葡萄糖为形式的碳。

Usually this happens at the cellular level and what's burned is carbon in the form of sugars, glucose.

在我们细胞中，氧通过化学反应与糖结合，化学反应产生能量来供给细胞。

Oxygen gets chemically combined with sugars in our cells and the energy produced from that reaction is then used to power the cells.

所以仅仅呼吸一次，你可以说我们都是碳排放的“罪人”，增加了大气中的碳含量。

So just by breathing you could say we are all guilty of carbon emission and contribute to the amount of carbon in the atmosphere.

有关大气中的碳的另一件事是：它让我们远离寒冷。

Student: Um, another thing about atmospheric carbon: it keeps us from freezing.

因为没有碳和其他温室气体，我们星球上的温度跟外太空是一样的，大概零上四度。

Because without carbon and other greenhouse gases, our planet would be the same temperature as outer space, around four degrees above absolute zero.

And there's nothing going on at that temperature.

所以没有大气中的碳，地球上不会有生命。

So without atmospheric carbon, life couldn't exist on Earth.

现在，还要记住另一件事，就是碳是总是从大气中清除掉。

Now, another thing to remember is that carbon is always being removed from the atmosphere.

大部分是被植物通过光合作用消耗掉。

Largely it’s consumed by plant life through photosynthesis.

而且它会溶解在海里或储藏在海底。

Also, it dissolves in the oceans or gets stored deep in the ocean.

有些贝壳类水生物用在水中溶解的二氧化碳去造碳酸钙的贝壳，并且当他们死后，他们身体沉入海底，碳就被隔绝在海底了。

You have shellfish that use the CO2 dissolved in the water to make carbonate shells and when they die, they fall to the ocean floor and the carbon gets sequestered down there.

所以因为碳持续性得从大气中消耗尽，我们真的需要提高碳产量让它维持在一个点上。

So with all this carbon constantly being depleted from the atmosphere, we really need to keep carbon output up to a certain point.

所以为什么还会有关于燃烧碳的那么多负面的新闻呢？

So why all the bad press for burning carbon?

嗯，结果表明燃烧的碳的来源是问题关键。

Well, turns out it's the source of the carbon being burned that's the key.

事实上是燃烧我们说的“化石碳”导致了这些不平衡：化石燃料，煤，石油，天然气。

It's in fact the burning of what we call "fossil carbon" that creates the imbalance: fossil fuels, coal, oil, natural gas.

我们必须要把他们挖出来或者钻一个井去得到他们。

We have to dig them up or drill a well to release them.

这些碳是几百万年前在大气中的碳。

And this is carbon that was in the atmosphere millions of years ago.

所以事情是这样的：让我们燃烧这些碳，ok，跟已经在大气中的碳相比，燃烧他们释放的碳不是很多，但是他们增加了大气的碳总量。

So what happens is: when we burn this carbon, ok, it doesn't really release a whole lot compared to the amount that's already there in the atmosphere, but it adds to the pool.

Think of the atmosphere as a big bathtub.

里面已经装满了很多碳，就快溢出来了。

It's basically already filled to the brim with carbon.

当我们开始增加化石碳进去，大气里的碳就开始溢出。

When we start adding fossil carbon into the mix, it starts to spill over.

虽这么说，事实上有一种碳形式是在两者之间的：我们叫生物燃料，最常见的可能就是木材。

That being said, there's actually a category that's in-between: what we call biomass fuels, probably the most common one is wood.

另一个例子，在北美平原上，当地人过去常常收集水牛的粪便去燃烧。

Another example, um, on the North American plains, the Native Americans used to collect buffalo droppings to burn.

在Ireland，人们把泥塘里的泥煤切下来去烧。

Uh, in Ireland, they cut up peat from bogs and they burn that.

所以这种碳和化石燃料有什么大的区别？

So what's the big distinction between this and fossil carbon?

生物燃料是我们说的流动性碳。

Biomass carbon is what we might call current carbon.

It's always going in and out of the atmosphere.

如果我们燃烧了其中的碳，我们增加了大气中的碳含量，对吗？

So if we burn one of these fuels, we're putting its carbon into atmosphere. Right?

但是在一个平衡的系统里，世界上另一个角落里会减少同等量的碳。

But in a balanced system, somewhere else in the world the same amount of carbon is going back.

通过种植植被把这部分碳消耗掉。

所以燃烧生物燃料产生的是那种不是很坏的碳。

So burning biomass fuel produces sort of not-so-bad carbon.

事实上，它可以成为好的碳如果我们整个社会整个人类努力让森林去消耗这些碳的话。如果我们不这么做，比如把地球上所有土地都为人类所用不让植物生长（他们就不会成为好的碳）。

In fact, it can become good carbon if we endeavor as a society, as humanity, to allow forests to recover this carbon, if we don't, say, pave over all the surfaces to prevent things from growing.

所以无论什么时候我们砍掉一棵树，燃烧了木材，我们必须让另一颗树去成长去平衡这个体系。

So whenever we cut down a tree and burn its wood, we have to allow another tree to grow to keep things in balance.

那样的话，你就创造了中性碳。

What is the main purpose of the lecture？

What aspects of outer space does the professor emphasize?Click on two answers.

According to the professor, how do the oceans remove carbon from the atmosphere?

What does the professor mean when he refers to biomass carbon as "current carbon”？

Now over the next few weeks we are going to focus on carbon and its roe on what is known as greenhouse effect. Everyone knows what that is, right? But let me show you, anyway. Yes, Kali?
The greenhouse effect is when gases and earth atmosphere act like the glass and the greenhouse or hot house. They trapping heat which warms up the earth.
Gases like?
Um…water vapor, carbon dioxide.
Right. Carbon dioxide. We hear lot about carbon these days. Know? Carbon emissions, carbon burning, living at carbon footprint. So it’d be easy to assume any form of carbon burning is necessarily a bad thing. But the fact is, it’s not quite that simple. So we are going to focus today on the difference between good and bad and, well, the not so bad, the potentially ok carbon burning.,
Ok, good carbon burning. Well, we all have personal stake in this, because carbon burning is the basis of life. We wouldn’t be here, if we are selves worn of burning carbon. Basically, all living things burn carbon to survive. Usually this happens at cellular lever, and what’s burned is carbon in the form of sugars, . Oxygen gets chemically combined with sugar in our cells, and the energy produced in that reaction is used to power the cells. So just by breathing, you could see we are all guilty of carbon emission, and contribute to the amount of carbon in the atmosphere.
Another thing about atmosphere carbon, it keeps us from freezing. Because without carbon and other greenhouse gases, our planet will be the same temperature as the outer space, around 4 degrees above the absolute zero, and there is nothing going on in that temperature. No possibility of life of any sort. So without atmosphere carbon, life couldn’t exist on earth.
Now another thing to remember is that carbon is always being removed from atmosphere. It gets used up. Largely, it’s consumed by plant life though photosynthesis. Also, it dissolves in the oceans or get stored deep in the ocean. You have shellfish that use the CO2 dissolved in the water to make carbon its shells and when they die, they fall to the ocean floor, and carbon gets sequestered down there. So without this carbon constantly being depleted from the atmosphere, we really need to keep carbon pulled up to a certain point.
So why all the bad for burning carbon? Well, turns out it’s the source of carbon being burned that’s the key. It’s in fact the burning of what we call fossil carbon that creates the imbalance. The fossil fuels, they call oil natural gas, these substances are all mined, we have them dig up, or drill a well to release them. And this is carbon that was in the atmosphere millions of years ago. So what happens is when we burn this carbon, ok, you doesn’t release a lot compared to the amount in the atmosphere. But it adds to the poor. And over years, it accumulates. Think of the atmosphere as a big , it basically already fill the brim with carbon, when we start adding fossil carbon to the mix, it starts to spill over. That being sad, there is actually a category that’s in between, what we call bio mass fuels. Probably the most common one is wood. Another example on the North American plains, the native Americans use the collected buffalo drops to burn. In Ireland, they cut up pieces from boughs and they burn that.
So what’s the big distinction between this and fossil carbon? Bio mass carbon is we might call current carbon. It always goes in and out the atmosphere. So if we burn one of this fuels, we are putting its carbon in the atmosphere, right? But in the balance system, somewhere else in the world the same amount of carbon is going back. It gets taken in by growing vegetation. So burning bio mass fuel produces sort of not so bad carbon. In fact, it can become good carbon, if we endeavor, as a society, as humanity, to allow forests to recover this carbon, if we don’t, say pay overall to surfaces, to prevent things from going. So whenever we cut down the tree and burn its wood, we have to allow another tree to grow, to keep things in balance. That way, your carbon neutral.
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