Can clouds buy us more time to solve climate change? | Kate Marvel

翻译人员: Lipeng Chen 校对人员: Conway Ye

I am a climate scientist,

我是一名气象学家，

and I hate weather.

我讨厌天气。

I have spent too much time in California,

我在加利福尼亚州待了太长时间，

and I strongly feel that weather should be optional.

我强烈的认为天气 应该是可有可无的。

(Laughter)

（笑声）

So I don't want to experience clouds,

我不想看见天上的云，

let alone study them.

更不要说研究它们了。

But clouds seem to follow me wherever I go.

但是我到哪里，云就跟到哪里。

The thing is, clouds are a real challenge for climate science.

事实上，研究云对于 气象学来说是一个挑战。

We don't know how they're going to react as the planet heats up,

我们不知道随着地球的升温， 它们会如何变化，

and hidden in that uncertainty

而蕴藏在那不确定性之中的，

might be hope.

可能是希望。

Maybe, just maybe,

也许，只是也许，

clouds could slow down global warming,

云可以减缓气候变暖的速度，

and buy us a little bit more time to get our act together,

可以给我们的团结行动争取一点时间，

which would be very convenient right now.

而现在这很重要。

I mean, even I could put up with a few more cloudy days

我想说，如果云可以拯救地球的话，

if clouds saved the planet.

我宁愿多忍受几天的多云天。

Now, we are sure about some things.

现在，我们已经确认了某些事情。

Carbon dioxide is a greenhouse gas,

二氧化碳是一种温室气体，

we're emitting a lot of it,

我们大量排放，

and the planet is heating up.

而地球在升温。

Case closed.

事情就是这样。

But I still go to work every day.

但是我每天仍去工作。

It turns out that there is a lot that we don't understand

事实是，我们对于气候变化

about climate change.

还有很多不知道的地方。

In particular, we haven't answered

特别的，我们没有回答

what seems to be a very fundamental question.

一个看上去十分基本的问题。

We know it's going to get hot,

我们知道会变得更热，

but we don't know exactly how hot it's going to get.

但是我们并不知道会变得多热。

Now, this is a really easy question to answer

如果你们能给我一台时间机器，

if one of you would like to give me a time machine.

这会是一个十分简单的问题。

But I'm going to be honest with you:

但是我想和你们开诚布公，

if I had a time machine,

如果我有一台时间机器，

I would not be hanging out at this particular point in history.

我不会去历史上的这个时间点。

So in order to see the future,

为了预测未来，

we have to rely on the output of computer simulations --

我们需要依靠电脑模拟的结果，

climate models, like this one.

气候模型，就像这个一样。

Now, in my line of work,

现在，在我的工作中，

I encounter many very charming people on the internet

我在网上遇到了许多人

who like to tell me that climate models are all wrong.

告诉我气候模型都是错的。

And I would just like to say:

而我只想说：

no kidding!

不是开玩笑！

Seriously? I get paid to complain about climate models.

认真的吗？我拿着工资来抱怨气候模型。

But we don't want models to be perfect.

但是我们不希望模型是完美的。

We want them to be useful.

我们希望它们是有用的。

I mean, think about it:

我想说，想想这个：

a computer simulation

一个可以

that's able to exactly reproduce all of reality.

准确复制所有现实的电脑模拟。

That's not a climate model;

那不是气候模型，

That's "The Matrix."

那是《黑客帝国》。

So, models are not crystal balls.

所以，模型不是水晶球。

They're research tools,

它们是研究工具，

and the ways in which they're wrong can actually teach us a lot.

它们在某些方面的错误， 事实上可以教我们很多。

For example:

比方说：

different climate models are largely able to capture

不同的气候模型大多可以捕捉

the warming that we've seen so far.

我们现在见证的气候变暖。

But fast-forward to the end of the century

但是如果情形不变

under a business-as-usual scenario,

快进到本世纪末，

and climate models don't really agree anymore.

气候模型的结果不再一致。

Yeah, they're all warming; that's just basic physics.

是的，它们都预测变暖， 这只是基本的物理。

But some of them project catastrophe --

但是有些预测灾难性的后果，

more than five times the warming we've seen already.

是我们现在见证的变暖的五倍。

And others are literally more chill.

其他的要更冷一些。

So why don't climate models agree on how warm it's going to get?

那么为什么气候模型不能在 会有多暖这个问题上达成一致呢？

Well, to a large extent,

大致上来说，

it's because they don't agree on what clouds will do in the future.

这是因为它们对云 在未来起的作用不一致。

And that is because, just like me,

这是因为，就像我一样，

computers hate clouds.

电脑讨厌云。

Computers hate clouds because they're simultaneously very large

电脑讨厌云，因为它们既很大，

and very small.

又很小。

Clouds are formed

当微小的水滴或冰晶

when microscopic water droplets or ice crystals coalesce

在细微颗粒物上附着时，

around tiny particles.

云便形成了。

But at the same time, they cover two-thirds of the earth's surface.

但是同时， 它们覆盖了地球三分之二的表面。

In order to really accurately model clouds,

为了真真正正的模拟云，

we'd need to track the behavior of every water droplet and dust grain

我们需要追踪整个大气层里，

in the entire atmosphere,

每个水滴和颗粒物的行踪，

and there's no computer powerful enough to do that.

而没有计算机可以强大到这个地步。

So instead, we have to make a trade-off:

所以，我们要做一个权衡：

we can zoom in and get the details right,

我们可以放大，把细节做对，

but have no idea what's going on worldwide;

但是没有办法知道全世界范围内会怎么；

or, we could sacrifice realism at small scales

或者，我们可以牺牲细节层面上的真实，

in order to see the bigger picture.

以看到全局。

Now, there's no one right answer,

现在，没有一个正确的答案，

no perfect way to do this,

没有一个完美的方法，

and different climate models make different choices.

而不同的气候模型指向不同的选择。

Now, it is unfortunate

电脑受制于云的存在，

that computers struggle with clouds,

这是非常不幸的，

because clouds are crucially important

因为云对于调节全球的气温，

in regulating the temperature of the planet.

起到了关键性的作用。

In fact, if all the clouds went away,

事实上，如果没有云，

we would experience profound climate changes.

我们会经历猛烈的气候变化。

But without clouds,

但是没有云，

would it be warmer or colder?

是会变的更热，还是更冷呢？

The answer is both.

两个都是答案。

So I'm going to be honest with you, I am not a cloud spotter.

实话对你们说， 我不一直看着云。

My favorite type of cloud is none.

我不喜欢任何种类的云。

But even I know that clouds come in all shapes and sizes.

但是我知道云有不同的形状和大小。

Low, thick clouds like these are really good at blocking out the sun

像这种低、厚的云可以很好的挡住太阳，

and ruining your barbecue,

毁掉你的野餐，

and high, wispy clouds like these cirrus

而像这卷云一样的高、轻薄的云

largely let that sunlight stream through.

则会让阳光透过。

Every sunny day is the same,

每个大晴天都是一样的，

but every cloudy day is cloudy in its own way.

但是每个多云天则各有不同。

And it's this diversity

而正是这种多样性

that can make the global impact of clouds very hard to understand.

使得理解全球范围内云的影响变得困难。

So to see this global effect of clouds,

所以为了考察云的全球影响，

it really helps to take a selfie.

拍张自拍是很有用的。

It will never cease to blow my mind

我们能从外太空看到我们的星球，

that we can see our planet from outer space,

这一点一直为我所惊诧，

but we can't see all of it.

但是我们不能看到它的全部。

Clouds are blocking the view.

云挡住了视野。

That's what they do.

这就是它们所做的。

These low, thick clouds are extremely effective sunshades.

这些低、厚的云朵是非常有效的遮阳蓬。

They turn back about 20 percent of everything the sun sends us.

它们反射回将近20%的太阳光。

That is a lot of wasted solar power.

那浪费了很多太阳能。

So, low clouds are powerful sunshades,

所以，低空的云朵是有力的遮阳蓬，

making the planet cooler.

让地球变凉爽。

But that's not the only effect of clouds.

但是这不是云的唯一效果。

Our planet has a temperature,

我们的星球有温度，

and like anything with a temperature,

就像任何有温度的物体一样，

it's giving off heat.

它会散热。

We are radiating thermal energy away into space,

我们将热能辐射到宇宙之中，

and we can see this in the infrared.

这可以在红外线中观测到。

Once again, clouds are blocking the view.

又一次，云挡住了。

That's because high clouds live in the upper reaches of the atmosphere,

这是因为在十分寒冷的大气层上侧，

where it's very cold.

存在着高层云朵。

And this means that they lose very little heat to space themselves.

这意味着它们本身只会损失很少的热量到宇宙中。

But at the same time, they block the heat coming up from the planet below.

但是同时，它们挡住了 从下方地球散发出来的热量。

The earth is trying to cool itself off,

地球想要变凉快些，

and high clouds are getting in the way.

但是高空云朵挡住了（热量的）去路。

The result is a very powerful greenhouse effect.

结果就是十分强烈的温室效应。

So, clouds play this very large and dual role

所以，云在气象系统中

in the climate system.

扮演着这个巨大的双重角色。

We've got low clouds that act like a sunshade,

我们有像遮阳蓬一样的低空云朵来

cooling the planet,

给地球降温，

and high clouds which act like a greenhouse,

还有类似温室气体作用的高空云朵来

warming the planet.

给地球升温。

Right now, these two effects -- they don't cancel out.

现在，这两种效应—— 它们不相互抵消。

That sunshade -- it's a little bit more powerful.

那遮阳蓬——影响更大些。

So if we got rid of all the clouds tomorrow,

所以如果明天我们把云都弄掉，

which, for the record, I am not advocating,

注意一下，我不是在辩护，

our planet would get warmer.

我们的星球会变得更热。

So clearly, all of the clouds are not going away.

显然，云是不会消散的。

But climate change is change.

但是气候在变化。

So we can ask:

所以我们会问：

How will global warming change clouds?

全球变暖会怎么改变云？

But remember, clouds are so important

但是记住，云在调节地球温度这件事上

in regulating the earth's temperature,

起着十分重要的作用，

and they both warm and cool the planet.

它们同时提高且降低这地球的温度。

So even small changes to cloud cover

所以即使是云的覆盖变化了一点点，

could have profound consequences.

也会有很大的影响。

So we might also ask:

我们还会问：

How will clouds change global warming?

云会如何影响全球变暖？

And that is where there might be space for hope.

这可能是希望之所在。

If global warming triggers cloud changes

如果全球变暖引起的变化

that make for a less powerful greenhouse or a more effective sunshade,

减弱了温室效应或是增强了遮阳蓬，

then that would enhance the cooling power of clouds.

那么便会加强云的制冷能力。

It would act in opposition to global warming,

这会产生与全球变暖相反的效果，

and that's what's happening in those climate models

正是在那些预测变暖相对缓和的

that project relatively muted warming.

模型中所发生的。

But climate models struggle with clouds,

但是气候模型受制于云，

and this uncertainty -- it goes both ways.

以及这种不确定性——是把双刃剑。

Clouds could help us out with global warming.

云可以把我们从全球变暖中解救出来。

They could also make it worse.

它们也可以使得情况变糟。

Now, we know that climate change is happening

现在，我们知道气候变化正在发生，

because we can see it:

因为我们见证了：

rising temperatures, melting icecaps, shifts in rainfall patterns.

升高的气温，融化的冰盖，改变的降雨模式。

And you might think that we could also see it in the clouds.

你可能认为我们在云上也见到了改变。

But here's something else unfortunate:

但是非常不幸：

clouds are really hard to see.

云很难观察。

I see everybody from the Pacific Northwest

我遇到每个来自美国西北部的人

is like, "I have some suggestions for you."

差不多都是“我想给提些建议。”

(Laughter)

（笑声）

And you guys, we have tried looking up.

伙计，我们尝试过（那些建议）。

(Laughter)

（笑声）

But in order to do climate science,

但为了气象科学研究，

we need to see all of the clouds, everywhere, for a very long time.

我们需要观测所有的云， 每个地方，并持续很长时间。

And that's what makes it hard.

这就让事情难办了。

Now, nothing sees more clouds than a satellite --

现在，没有东西可以比卫星观测更多的云——

not even a British person.

连英国人也不行。

(Laughter)

（笑声）

And fortunately, we do have satellite observations of clouds

幸运的是，我们有很多云的卫星观测，

that, like me, date back to the 1980s.

就像我一样，最早到上世纪八十年代。

But these satellites were designed for weather,

但是这些卫星是为天气服务的，

not climate.

而不是气候。

They weren't in it for the long haul.

它们不是为了持久战。

So to get that long-term trend information,

所以为了获得长期趋势信息，

we need to do climate science.

我们需要进行气象科学研究。

We have to stitch together the output of multiple satellites

我们需要用不同的观测视角和观测轨道，

with different viewing angles and orbits

以及不同的摄像设备，

and carrying different camera equipment.

将不同卫星的输出整合起来。

And as a result,

作为结果，

there are gaps in our knowledge.

我们的知识中存在盲点。

But even from this very cloudy picture,

但是即使从这些非常模糊的图像中，

we're starting to get hints of a possible future.

我们开始看到可能的未来的线索。

When we looked at the observations,

当我们研究这些观测时，

one thing jumped out at us:

一件事情跃然纸上：

the clouds are moving.

云在移动。

As the planet's temperature increases,

随着地球温度升高，

high clouds rise up.

高层云朵上升。

They move to the colder upper reaches of the atmosphere,

它们移到了更冷的大气层上侧，

and this means that even as the planet heats up,

这意味着即使地球在变暖，

high clouds don't.

高层云朵并不这样。

They remain at roughly the same temperature.

它们保持着差不多相同的温度。

So they are not losing more heat to space.

所以它们没有损失更多的热量到宇宙中。

But at the same time, they're trapping more heat

但同时，它们困住了更多的

from the warming planet below.

来自下方变暖的地球的热量。

This intensifies the greenhouse effect.

着加剧了温室效应。

High clouds are making global warming worse.

高层云朵使得全球变暖变得更糟。

Clouds are moving in other dimensions, too.

云也在其他层面移动。

The atmospheric circulation, that large-scale motion

大气环流，

of air and water in the atmosphere,

即大气中大范围的空气和水的移动，

is changing,

在变化，

and clouds are going with it.

而且云随之而动。

On large scales,

大范围来看，

clouds seem to be moving from the tropics toward the poles.

云看上去从赤道移向了两极。

It's kind of like your grandparents in reverse.

这就像你祖父母在返老还童一样。

And this matters,

这很重要，

because if your job is to block incoming sunlight,

因为如果你的职责是挡住过来的太阳光，

you are going to be much more effective in the tropics

挡住赤道那强烈的阳光

under that intense tropical sun

要比在高纬度

than you are in higher latitudes.

更加有效。

So if this keeps up,

如果这种情况持续，

this will also make global warming worse.

全球变暖也会加剧。

And what we have not found,

尽管有多年的观测，

despite years of looking,

我们仍没发现，

is any indication of the opposite.

任何相反的迹象。

There is no observational evidence

没有观测证据显示

that clouds will substantially slow down global warming.

云可以显著的降低全球变暖的速度。

The earth is not going to break its own fever.

地球不能自己治愈发热。

Now, there are still uncertainties here.

现在，仍然存在不确定性。

We don't know for sure

我们不准确知道

what the future holds.

未来会怎么样。

But we are sending our kids there,

但是我们把我们的孩子送往那里，

and they are never coming back.

他们永远不会回来。

I want them to be prepared for what they'll face,

我想让他们为他们将要面对的做好准备，

and that is why it is so important

这就是为什么让我们的地球观测卫星

to keep our earth-observing satellites up there

继续在太空运作，

and to hire diverse and smart and talented people

以及雇用不同的、聪明的、有才能的、

who do not hate clouds

而且不讨厌云的人，来改进气候模型

to improve the climate models.

十分重要的原因。

But uncertainty is not ignorance.

但是不确定性不容忽视。

We don't know everything,

我们不知道所有事情，

but we don't know nothing,

但我们不是一无所知，

and we know what carbon dioxide does.

我们知道二氧化碳所做的。

I started my career as an astrophysicist,

我以天体物理学家作为职业起步，

so you can believe me

所以你们可以相信我，

when I say that this is the greatest place in the universe.

我说地球是宇宙中最棒的地方。

Other planets might have liquid water.

其他星球可能有液态水。

On earth, we have whiskey.

地球上，我们有威士忌。

(Laughter)

（笑声）

(Applause)

（掌声）

We are so lucky to live here,

我们能居住于此太幸运了，

but let's not push our luck.

但让我们不要用尽好运。

I don't think that clouds will save the planet.

我不认为云会拯救地球。

I think that's probably up to us.

我认为那取决于我们。

Thank you.

谢谢。

(Applause)

（掌声）