How Aerosols Brighten Clouds — and Cool the Planet | Sarah J. Doherty | TED

翻译人员: Lening Xu 校对人员: Sue Lu

So I'm a climate scientist,

我是一名气候科学家,

and based on that,

基于此，

I bet you think I'm here to tell you about all the ways

我敢打赌，你们认为我会告知你们

that we're making the climate warmer.

使得气候变暖的所有行为。

But I'm not actually going to do that today

实际上我并不打算那样做，

because I think you already know that part of the story.

因为我想你们已经了解那些故事了。

I want to tell you instead a story about unintended consequences.

相反，我想给你们讲 一个关于意外后果的故事。

For many of us, it's really easy to forget

对于许多人来说，很容易忘记

除了排放大量的温室气体外，

that in addition to emitting a lot of greenhouse gases,

humans have been adding a lot of particulate pollution

人类还在大气中增加了 大量的颗粒物污染。

to the atmosphere.

These small particles, which we scientists call aerosols,

这些小颗粒， 科学界称之为气溶胶，

are responsible for the death of between four and 10 million people a year

每年致使全球四百万到一千万人死亡。

around the globe.

For much of the world, this remains a major public health crisis.

对于世界上大部分地区来说， 这仍然是一个重大的公共卫生危机。

And because of that, there are significant efforts underway

正因为如此， 人们正在努力清理这些排放源，

to clean up the source of these emissions,

which is fantastic.

这太棒了。

But here's the thing.

但问题是这样的。

The unintended consequence of doing that

这样做的意想不到的后果是，

is that we might actually be accelerating climate warming.

我们实际上可能正在加速气候变暖，

And that's because most of these aerosols actually cool climate.

因为大多数气溶胶能够冷却气候。

I spent my career as a climate scientist

我的职业是一名气候科学家，

studying how aerosols in the atmosphere around the globe

研究全球大气中的气溶胶

absorb sunlight in the atmosphere

如何吸收大气中的阳光，

and increase the reflection of sunlight away from our planet.

且增加阳光反射回太空的量。

Aerosols directly scatter sunlight back to space,

气溶胶直接将阳光散射回太空，

and when they mix into clouds,

当它们混入云层时，

they can make clouds brighter or more reflective.

可以使云层更亮或更具反射性。

And both of these effects act to cool the climate

这两种效果都可以冷却气候，

by reducing the amount of sunlight that's available to heat the surface.

通过减少可用于加热 地表的阳光量来实现。

We estimate that right now,

我们估计，目前，

aerosols from human activities are cooling climate

来自人类活动的气溶胶使气候降温

by about half a degree Celsius.

约半摄氏度。

In other words, if it weren't for these climate effects,

换句话说，如果不是这些气候效应，

we would already be experiencing significantly worse climate impacts

我们经历的气候影响就会

than we already are.

比现在严重得多。

So here's a conundrum.

因此，这是一个难题。

As we clean up the air for human health,

当我们为人类健康清理空气时，

we're reducing the concentration of these aerosols in the atmosphere,

我们降低了这些气溶胶 在大气中的浓度，

and we're removing the source of climate cooling.

也就是消除了气候降温的根源。

And because these aerosols only last in the atmosphere for about a week,

而且，由于这些气溶胶 只能在大气中持续约一周，

their cooling effect goes away almost immediately

一旦我们停止排放， 其冷却效果几乎立即消失。

after we stop emitting them.

Unlike greenhouse gases,

而温室气体则会持续升温 数十年至数百年。

which continue to warm for decades to centuries.

Here's a second conundrum.

第二个难题是，

While our best estimate is that aerosols are cooling climate

虽然最乐观的估计 是气溶胶使气候降温

by about half a degree Celsius,

约半摄氏度，

this effect could be quite a bit smaller,

但这种效应可能会小得多，

or it could be a lot bigger.

也可能更大。

It's possible that aerosols right now are cooling climate

by up to almost a full degree Celsius.

高达一摄氏度。

And because we don't know

而且，由于我们不知道

how much of a cooling effect these aerosols are currently providing,

we don't know how much of a climate warming they're going to unmask

所以我们不知道当我们清理空气时，

as we clean up the air.

会暴露多少气候变暖的真相。

So let's step back and talk a little bit more

因此，让我们退后一步，

about how it is that aerosols cool climate

再谈谈气溶胶如何使气候降温，

and why these effects are so uncertain.

以及这些效应为何如此不确定。

So aerosols mostly cool climate

气溶胶降温主要

by increasing the reflection of sunlight from clouds.

通过增加云层对阳光的反射。

This increase in cloud brightness from aerosols

气溶胶导致的云层亮度增加

is not generally very visibly apparent

通常不太明显，

because clouds are just so naturally variable in their brightness.

因为云的亮度会自然变化。

But a case where it is really visually obvious

但是，也有显而易见的例子，

is in what we call ship tracks.

就是我们所谓的“船舶轨迹”。

So what you're looking at here is a satellite image

你现在看到的是 北美西海岸的卫星图像。

off the west coast of North America.

And you can see that there are these lines of clouds

这些成线的云 比周围的云更亮或反射性更强。

that are brighter or more reflective than the clouds around them.

So to understand what's going on here,

因此，要了解这里发生了什么，

you first have to know that cloud droplets always form on an aerosol.

你首先要了解云滴 总是在气溶胶上形成。

Out over the ocean, there's just not generally that many aerosols

在海面上空， 大气中的气溶胶通常不多。

in the atmosphere.

So what you end up with

因此，最终形成的

is a cloud with a small number of larger droplets.

是一团含有少量大液滴的云。

Well, along comes your ship,

然后，当船舶驶过时，

and it's adding aerosols to the atmosphere

它会向大气层和云层中添加气溶胶。

and to the clouds.

The water gets distributed over those aerosols,

水便分布在这些气溶胶上，

and you now have a cloud with a large number of smaller droplets.

形成带有大量小液滴的云层。

This change in droplet size increases the reflectivity of the cloud.

液滴的大小变化增加了云的反射率。

Now this is not just happening where ship emissions are mixing into clouds.

这种情况不仅发生在船舶 排放物混入云层的地方。

This is actually mostly happening over broad regions of the planet

事实上，这种情况大多发生在地球上 污染气溶胶混合成云的广阔区域。

where pollution aerosols mix into clouds.

So I've shown you here a very striking example

我在这展示的是个非常显著的例子，

of where pollution aerosols are clearly making clouds more reflective.

说明污染气溶胶使云层更具反射性。

But this actually doesn't always happen.

但这实际上并不经常发生。

And why is that?

那是为什么？

Well, I'm going to give you scientists' two very favorite answers.

我要给你们两个 科学家们最喜欢的答案。

It’s complicated. And it depends.

情况很复杂。 这要视情况而定。

(Laughter)

（笑声）

If you have ever looked at clouds for very long,

如果你长时间观察云层，

you could see that they’re incredibly complex,

就会发现它们非常复杂，

and they are constantly evolving.

不断在演变。

When you add aerosols to clouds,

当你向云中添加气溶胶时，

it doesn't just change their droplet size,

它不仅会改变其液滴的大小，

it actually can then change how they evolve

也能改变它们的演变方式，

in ways that also affect cloud brightness.

从而影响云层的亮度。

Depending on the details of the atmospheric conditions,

根据大气条件的具体情况，

clouds can be made either more or less reflective with the addition of aerosols,

添加气溶胶可以使 云层反射性增强或减弱，

or not really changed at all.

或者基本不变。

But what we do know is that under the right conditions,

但我们确知的是，在适当条件下，

aerosol additions to clouds can make them quite a bit brighter.

添加气溶胶可以使云层变得更亮。

So this poses an interesting question.

因此，这就提出了一个有趣的问题。

Might it be possible to rapidly reduce climate warming

是否能快速减缓气候变暖，

通过模仿污染气溶胶对云层产生的效应？

by mimicking this effect

that pollution aerosols are already having on clouds,

but do so by adding natural aerosols rather than pollution to clouds?

当然，模仿时会向云层添加 天然的而不是污染气溶胶。

Specifically by adding sea salt aerosol to clouds over the ocean,

具体而言，就是向海洋 上空的云层添加海盐气溶胶，

where sea salt aerosols already act as seeds for cloud droplet formation.

海盐气溶胶已经成为云滴形成的种子。

Well we start with studying this problem using computer models.

我们首先使用计算机模型 研究这个问题。

And when we add tiny sea salt aerosols to the clouds over the ocean

当我们向全球气候模型中的海洋云层 添加微小的海盐气溶胶时，

in global climate models,

we find that brightening just a fraction of the clouds over the ocean

我们发现，仅使海洋上空 云层的一小部分变亮，

does, in fact, rapidly and significantly reduce climate warming

就可以迅速而显著地 减少温室气体造成的气候变暖。

from greenhouse gases.

So these models indicate it is possible.

因此，这些模型表明这是可能的。

But here's the problem.

但问题是，

These global-scale models

这些用于研究海洋云层变亮 对气候影响的全球性模型，

used to study the climate impacts of marine cloud brightening,

lack the ability to resolve all of these detailed interactions

缺乏解析气溶胶和云层之间 所有相互作用细节的能力，

between aerosols and clouds.

So they can't tell us how much cloud brightening is possible or where.

无法告诉我们云层 可以在哪里达到什么亮度。

For that problem,

为了解决这个问题，

we have to turn to models that cover much more localized areas of the globe

我们必须求助于覆盖全球 更多局部区域的模型，

but that include many, many more details about aerosols, clouds

而它应该包含气溶胶、云层 及其相互作用的更多细节。

and how they interact.

So what we really need is better real-world data

因此，我们真正需要的是 更好的真实数据，

that we can use to test and inform these models

可以用来测试和训练这些模型，

that we use to study marine cloud brightening.

用于研究海洋云层的增亮。

Now with this problem, as with many problems in the world,

现在这个问题， 就像世界上许多问题一样，

the devil is in the details.

是细节决定成败。

Many of the most uncertain aspects

海洋云层变亮的可能性中 许多最不确定的方面

of the potential for marine cloud brightening

have to do with how really small-scale air motions in clouds,

都与云层中的小规模空气运动有关，

we're talking over like a few square kilometers,

我们说的是几平方公里云层，

respond to the addition of aerosols.

对气溶胶的增加的反应。

So being able to systematically study how clouds respond to aerosols,

因此，如果能够系统地研究云层 对气溶胶的反应，

just like a single plume of aerosols,

哪怕是一小片云层和上面的一股气溶胶，

over a small area of clouds,

could go a long way to improving these climate models.

也可以大大改善这些气候模型。

And I want to tell you today about a powerful approach

今天，我想向大家介绍一下

that our team is developing to do just that.

我们的团队为实现这一目标 正在开发的一种相当有用的方法。

So based on what I just said,

根据我刚才所说的，

you probably won't be surprised to learn

你可能并不感到惊讶

that that approach is to add a single plume of sea salt aerosols

这种方法是在海洋上空的一小片云层中 添加一股海盐气溶胶羽流，

to a small area of clouds over the ocean

and see how those clouds respond.

然后观察云层会如何反应。

Basically, to make a single clean ship track.

基本上，就是制造一条 清晰的船舶轨迹。

Now, the observations for studies like this

现在，此类研究的观测

would look a lot like those we've been doing for decades

将与我们几十年来研究污染气溶胶 如何影响云层的观测非常相似。

to study how pollution aerosols are already affecting clouds.

Research aircraft filled with specialized instruments

装有专门仪器的研究专用飞机

can be used to measure in great detail the atmospheric conditions

可以用来详细测量 大气条件、气溶胶、云层

the aerosols, the clouds

and how they all vary.

以及它们之间的变化。

The difference between what we've done here in the past

and what we would do with these new controlled aerosol studies,

这些新的受控气溶胶研究，

is that we would be able to actually compare clouds

因为现在可以实际比较

that have different aerosol concentrations

气溶胶浓度不同 但其他方面相同的云层。

but that are otherwise the same.

This would allow us to quantify where changes in cloud reflectivity

这样我们就能够量化云层反射率变化，

are actually being caused by the aerosols,

测出哪些是由气溶胶引起的，

rather than just varying due to other factors.

哪些仅是其他因素引起的。

Now it turns out that generating the sea salt aerosol plume

现在事实证明， 为进行这些 受控气溶胶研究生成

with the right characteristics for doing these controlled aerosol studies

具有正确特性的海盐气溶胶羽流

is a significant technological challenge.

是一项重大的技术挑战。

The aerosols need to be just right.

气溶胶必须恰到好处。

To date,

迄今为止，

no one has demonstrated the ability to generate

还没有人有能力

both the size and quantity of aerosols you would need to do these studies

同时产生大小和数量都恰好的气溶胶，

where you would consistently and appreciably brighten marine clouds.

可以持续显著地照亮海洋云层。

As a climate scientist trying to better understand

作为气候科学家，我试图更好地了解

how aerosols affect clouds and climate,

气溶胶如何影响云层和气候，

I am really thrilled to be part of a team

所以很高兴能加入开发新仪器 来应对这一挑战的团队。

that is developing a new instrument to meet that challenge.

Our new cloud aerosol research instrument is specifically designed

我们的新云气溶胶研究仪器

to generate a very large number of very, very tiny sea salt aerosols.

是专门为生成大量非常 微小的海盐气溶胶设计的。

These aerosols are about 1,000th of the width of a human hair,

这些气溶胶的宽度约为 人类头发的千分之一，

because that's the size that's ideal for marine cloud brightening.

因为这种大小非常适合增亮海洋云层。

I'm also really excited to be able to tell you

我也很高兴能够告诉你，

that we've just started our first scientific studies with this instrument.

我们刚刚使用这种仪器 开始第一次科学研究。

This happened just two weeks ago.

这发生在两周前。

We've set up our new Coastal Atmospheric Aerosol Research and Engagement Facility

我们在加利福尼亚阿拉米达的“黄蜂号”

on the flight deck of the USS Hornet Sea, Air and Space Museum

海空航天博物馆的飞行甲板上

in Alameda, California.

建立了新的沿海大气气溶胶研究和参与设施。

So on the Hornet,

因此，在 “黄蜂号” 上，

we are making observations at multiple locations

我们在飞行甲板多个地点 观测海盐气溶胶羽流，

along the flight deck

of the sea salt aerosol plume

它是由新仪器生成的。

that is being generated with our new instrument.

These measurements are going to allow us to study how the aerosol evolves

这些测量让我们能够研究 气溶胶在向云层传输时的演变，

as it's transported towards clouds.

It's also letting us study whether or not this instrument is delivering

以及该仪器是否能够提供

the right aerosol, with the right characteristics

正确的气溶胶以供 后续海上研究、单羽实验

for use in later studies at sea,

of the single plume experiment and how clouds respond.

以及云层的反应方式。

We've set up this study specifically at a museum

我们专门在博物馆设立这项研究，

to make it easily accessible to the public,

以方便公众、教育工作者和 其他研究人员参观。

educators and other researchers.

And we consider this level of openness

这种开放程度是计划中很重要的一部分。

to be a really important part of our program.

And that's because we're hoping

因为我们希望

that the work at the CAARE research facility

CAARE 研究机构的工作

can be the start of broader international engagement in this research,

能够成为国际上 广泛参与这项研究的开始，

particularly by our colleagues in historically marginalized communities

特别是对于我们历史上 被边缘化社区的同事，

who are the most vulnerable to climate change.

他们最容易受到气候变化影响。

Their direct engagement in this research is absolutely critical

所以他们直接参与这项研究至关重要，

to having equitable and informed discussions

有助于展开公平知情的讨论，

about whether we ever would use marine cloud brightening to cool climate

比如，是否使用海云增亮降温气候

as a way of addressing climate risks.

作为应对气候风险的一种方式。

Now don’t get me wrong,

别误会我的意思，

marine cloud brightening will not reverse the effects of greenhouse gases.

海洋云层增亮不会逆转温室气体效应，

This is not a solution to the climate crisis.

这不是气候危机的解决方案。

I really have to repeat that.

我真的得再说一遍。

This is not a solution to the climate crisis.

这不是气候危机的解决方案。

However, marine cloud brightening might be a way of treating

但是，海云增亮可能是改善

the main symptom of the problem,

问题主要症状的一种方法，

which is too much heat in the atmosphere and ocean.

即大气和海洋中的热量过高。

We believe that the world needs the best information possible

我们认为世界需要最好的信息，

to decide whether approaches like marine cloud brightening

以决定诸如海云增亮之类的方法是否

might be a component of how we chart a safer course

可以成为我们制定 更安全的未来路线的组成部分，

into a future that now includes a rapidly and dangerously warming climate.

而未来面临着迅速而危险的气候变暖。

We also believe it's really critical

我们还认为，至关重要的是

that we better understand the evolving role of aerosols

更好地了解气溶胶在气候变化 和气候系统中不断演变的作用，

in climate change and the climate system

if we don't want to be flying blind

如果我们不想盲目面对未来 几十年的气候变化。

into the coming couple decades of climate change.

I hope that I've left you as excited as I am

我希望你像我一样兴奋，

about these new capabilities we're developing

因为这些正在开发的新能力, 将用来研究非常紧迫的问题。

to study these really important questions.

And I invite you all to come join us at our new CAARE research facility.

我邀请大家加入 我们的 CAARE 研究机构。

Thank you.

谢谢。

(Applause)

（掌声）