I am a climate scientist, and I hate weather. I have spent too much time in California, and I strongly feel that weather should be optional.
﻿我是一名气象学家， 我讨厌天气。 我在加利福尼亚州待了太长时间， 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, let alone study them. But clouds seem to follow me wherever I go.
我不想看见天上的云， 更不要说研究它们了。 但是我到哪里，云就跟到哪里。
The thing is, clouds are a real challenge for climate science. We don't know how they're going to react as the planet heats up, and hidden in that uncertainty might be hope. Maybe, just maybe, clouds could slow down global warming, and buy us a little bit more time to get our act together, which would be very convenient right now. I mean, even I could put up with a few more cloudy days if clouds saved the planet.
事实上，研究云对于 气象学来说是一个挑战。 我们不知道随着地球的升温， 它们会如何变化， 而蕴藏在那不确定性之中的， 可能是希望。 也许，只是也许， 云可以减缓气候变暖的速度， 可以给我们的团结行动争取一点时间， 而现在这很重要。 我想说，如果云可以拯救地球的话， 我宁愿多忍受几天的多云天。
Now, we are sure about some things. Carbon dioxide is a greenhouse gas, we're emitting a lot of it, and the planet is heating up. Case closed. But I still go to work every day. It turns out that there is a lot that we don't understand about climate change. In particular, we haven't answered what seems to be a very fundamental question. We know it's going to get hot, but we don't know exactly how hot it's going to get. Now, this is a really easy question to answer if one of you would like to give me a time machine. But I'm going to be honest with you: if I had a time machine, I would not be hanging out at this particular point in history. So in order to see the future, we have to rely on the output of computer simulations — climate models, like this one.
现在，我们已经确认了某些事情。 二氧化碳是一种温室气体， 我们大量排放， 而地球在升温。 事情就是这样。 但是我每天仍去工作。 事实是，我们对于气候变化 还有很多不知道的地方。 特别的，我们没有回答 一个看上去十分基本的问题。 我们知道会变得更热， 但是我们并不知道会变得多热。 如果你们能给我一台时间机器， 这会是一个十分简单的问题。 但是我想和你们开诚布公， 如果我有一台时间机器， 我不会去历史上的这个时间点。 为了预测未来， 我们需要依靠电脑模拟的结果， 气候模型，就像这个一样。
Now, in my line of work, I encounter many very charming people on the internet who like to tell me that climate models are all wrong. And I would just like to say: no kidding! Seriously? I get paid to complain about climate models. But we don't want models to be perfect. We want them to be useful. I mean, think about it: a computer simulation that's able to exactly reproduce all of reality. That's not a climate model; That's "The Matrix." So, models are not crystal balls. They're research tools, and the ways in which they're wrong can actually teach us a lot.
现在，在我的工作中， 我在网上遇到了许多人 告诉我气候模型都是错的。 而我只想说： 不是开玩笑！ 认真的吗？我拿着工资来抱怨气候模型。 但是我们不希望模型是完美的。 我们希望它们是有用的。 我想说，想想这个： 一个可以 准确复制所有现实的电脑模拟。 那不是气候模型， 那是《黑客帝国》。 所以，模型不是水晶球。 它们是研究工具， 它们在某些方面的错误， 事实上可以教我们很多。
For example: different climate models are largely able to capture the warming that we've seen so far. But fast-forward to the end of the century under a business-as-usual scenario, and climate models don't really agree anymore. Yeah, they're all warming; that's just basic physics. But some of them project catastrophe — more than five times the warming we've seen already. And others are literally more chill.
比方说： 不同的气候模型大多可以捕捉 我们现在见证的气候变暖。 但是如果情形不变 快进到本世纪末， 气候模型的结果不再一致。 是的，它们都预测变暖， 这只是基本的物理。 但是有些预测灾难性的后果， 是我们现在见证的变暖的五倍。 其他的要更冷一些。
So why don't climate models agree on how warm it's going to get? Well, to a large extent, it's because they don't agree on what clouds will do in the future. And that is because, just like me, computers hate clouds. Computers hate clouds because they're simultaneously very large and very small. Clouds are formed when microscopic water droplets or ice crystals coalesce around tiny particles. But at the same time, they cover two-thirds of the earth's surface. In order to really accurately model clouds, we'd need to track the behavior of every water droplet and dust grain in the entire atmosphere, and there's no computer powerful enough to do that. So instead, we have to make a trade-off: we can zoom in and get the details right, but have no idea what's going on worldwide; or, we could sacrifice realism at small scales in order to see the bigger picture. Now, there's no one right answer, no perfect way to do this, and different climate models make different choices.
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？ 大致上来说， 这是因为它们对云 在未来起的作用不一致。 这是因为，就像我一样， 电脑讨厌云。 电脑讨厌云，因为它们既很大， 又很小。 当微小的水滴或冰晶 在细微颗粒物上附着时， 云便形成了。 但是同时， 它们覆盖了地球三分之二的表面。 为了真真正正的模拟云， 我们需要追踪整个大气层里， 每个水滴和颗粒物的行踪， 而没有计算机可以强大到这个地步。 所以，我们要做一个权衡： 我们可以放大，把细节做对， 但是没有办法知道全世界范围内会怎么； 或者，我们可以牺牲细节层面上的真实， 以看到全局。 现在，没有一个正确的答案， 没有一个完美的方法， 而不同的气候模型指向不同的选择。
Now, it is unfortunate that computers struggle with clouds, because clouds are crucially important in regulating the temperature of the planet. In fact, if all the clouds went away, we would experience profound climate changes. But without clouds, would it be warmer or colder? The answer is both.
电脑受制于云的存在， 这是非常不幸的， 因为云对于调节全球的气温， 起到了关键性的作用。 事实上，如果没有云， 我们会经历猛烈的气候变化。 但是没有云， 是会变的更热，还是更冷呢？ 两个都是答案。
So I'm going to be honest with you, I am not a cloud spotter. My favorite type of cloud is none. But even I know that clouds come in all shapes and sizes. Low, thick clouds like these are really good at blocking out the sun and ruining your barbecue, and high, wispy clouds like these cirrus largely let that sunlight stream through. Every sunny day is the same, but every cloudy day is cloudy in its own way. And it's this diversity that can make the global impact of clouds very hard to understand. So to see this global effect of clouds, it really helps to take a selfie.
实话对你们说， 我不一直看着云。 我不喜欢任何种类的云。 但是我知道云有不同的形状和大小。 像这种低、厚的云可以很好的挡住太阳， 毁掉你的野餐， 而像这卷云一样的高、轻薄的云 则会让阳光透过。 每个大晴天都是一样的， 但是每个多云天则各有不同。 而正是这种多样性 使得理解全球范围内云的影响变得困难。 所以为了考察云的全球影响， 拍张自拍是很有用的。
It will never cease to blow my mind that we can see our planet from outer space, but we can't see all of it. Clouds are blocking the view. That's what they do. These low, thick clouds are extremely effective sunshades. They turn back about 20 percent of everything the sun sends us. That is a lot of wasted solar power. So, low clouds are powerful sunshades, making the planet cooler. But that's not the only effect of clouds. Our planet has a temperature, and like anything with a temperature, it's giving off heat. We are radiating thermal energy away into space, and we can see this in the infrared. Once again, clouds are blocking the view. That's because high clouds live in the upper reaches of the atmosphere, where it's very cold. And this means that they lose very little heat to space themselves. But at the same time, they block the heat coming up from the planet below. The earth is trying to cool itself off, and high clouds are getting in the way. The result is a very powerful greenhouse effect. So, clouds play this very large and dual role in the climate system. We've got low clouds that act like a sunshade, cooling the planet, and high clouds which act like a greenhouse, warming the planet.
我们能从外太空看到我们的星球， 这一点一直为我所惊诧， 但是我们不能看到它的全部。 云挡住了视野。 这就是它们所做的。 这些低、厚的云朵是非常有效的遮阳蓬。 它们反射回将近20%的太阳光。 那浪费了很多太阳能。 所以，低空的云朵是有力的遮阳蓬， 让地球变凉爽。 但是这不是云的唯一效果。 我们的星球有温度， 就像任何有温度的物体一样， 它会散热。 我们将热能辐射到宇宙之中， 这可以在红外线中观测到。 又一次，云挡住了。 这是因为在十分寒冷的大气层上侧， 存在着高层云朵。 这意味着它们本身只会损失很少的热量到宇宙中。 但是同时，它们挡住了 从下方地球散发出来的热量。 地球想要变凉快些， 但是高空云朵挡住了（热量的）去路。 结果就是十分强烈的温室效应。 所以，云在气象系统中 扮演着这个巨大的双重角色。 我们有像遮阳蓬一样的低空云朵来 给地球降温， 还有类似温室气体作用的高空云朵来 给地球升温。
Right now, these two effects — they don't cancel out. That sunshade — it's a little bit more powerful. So if we got rid of all the clouds tomorrow, which, for the record, I am not advocating, our planet would get warmer. So clearly, all of the clouds are not going away. But climate change is change. So we can ask: How will global warming change clouds? But remember, clouds are so important in regulating the earth's temperature, and they both warm and cool the planet. So even small changes to cloud cover could have profound consequences. So we might also ask: How will clouds change global warming?
现在，这两种效应—— 它们不相互抵消。 那遮阳蓬——影响更大些。 所以如果明天我们把云都弄掉， 注意一下，我不是在辩护， 我们的星球会变得更热。 显然，云是不会消散的。 但是气候在变化。 所以我们会问： 全球变暖会怎么改变云？ 但是记住，云在调节地球温度这件事上 起着十分重要的作用， 它们同时提高且降低这地球的温度。 所以即使是云的覆盖变化了一点点， 也会有很大的影响。 我们还会问： 云会如何影响全球变暖？
And that is where there might be space for hope. If global warming triggers cloud changes that make for a less powerful greenhouse or a more effective sunshade, then that would enhance the cooling power of clouds. It would act in opposition to global warming, and that's what's happening in those climate models that project relatively muted warming. But climate models struggle with clouds, and this uncertainty — it goes both ways. Clouds could help us out with global warming. They could also make it worse.
这可能是希望之所在。 如果全球变暖引起的变化 减弱了温室效应或是增强了遮阳蓬， 那么便会加强云的制冷能力。 这会产生与全球变暖相反的效果， 正是在那些预测变暖相对缓和的 模型中所发生的。 但是气候模型受制于云， 以及这种不确定性——是把双刃剑。 云可以把我们从全球变暖中解救出来。 它们也可以使得情况变糟。
Now, we know that climate change is happening because we can see it: rising temperatures, melting icecaps, shifts in rainfall patterns. And you might think that we could also see it in the clouds. But here's something else unfortunate: clouds are really hard to see. I see everybody from the Pacific Northwest is like, "I have some suggestions for you."
现在，我们知道气候变化正在发生， 因为我们见证了： 升高的气温，融化的冰盖，改变的降雨模式。 你可能认为我们在云上也见到了改变。 但是非常不幸： 云很难观察。 我遇到每个来自美国西北部的人 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, we need to see all of the clouds, everywhere, for a very long time. And that's what makes it hard. Now, nothing sees more clouds than a satellite — not even a British person.
但为了气象科学研究， 我们需要观测所有的云， 每个地方，并持续很长时间。 这就让事情难办了。 现在，没有东西可以比卫星观测更多的云—— 连英国人也不行。
(Laughter)
（笑声）
And fortunately, we do have satellite observations of clouds that, like me, date back to the 1980s. But these satellites were designed for weather, not climate. They weren't in it for the long haul. So to get that long-term trend information, we need to do climate science. We have to stitch together the output of multiple satellites with different viewing angles and orbits and carrying different camera equipment. And as a result, there are gaps in our knowledge. But even from this very cloudy picture, we're starting to get hints of a possible future.
幸运的是，我们有很多云的卫星观测， 就像我一样，最早到上世纪八十年代。 但是这些卫星是为天气服务的， 而不是气候。 它们不是为了持久战。 所以为了获得长期趋势信息， 我们需要进行气象科学研究。 我们需要用不同的观测视角和观测轨道， 以及不同的摄像设备， 将不同卫星的输出整合起来。 作为结果， 我们的知识中存在盲点。 但是即使从这些非常模糊的图像中， 我们开始看到可能的未来的线索。
When we looked at the observations, one thing jumped out at us: the clouds are moving. As the planet's temperature increases, high clouds rise up. They move to the colder upper reaches of the atmosphere, and this means that even as the planet heats up, high clouds don't. They remain at roughly the same temperature. So they are not losing more heat to space. But at the same time, they're trapping more heat from the warming planet below. This intensifies the greenhouse effect. High clouds are making global warming worse.
当我们研究这些观测时， 一件事情跃然纸上： 云在移动。 随着地球温度升高， 高层云朵上升。 它们移到了更冷的大气层上侧， 这意味着即使地球在变暖， 高层云朵并不这样。 它们保持着差不多相同的温度。 所以它们没有损失更多的热量到宇宙中。 但同时，它们困住了更多的 来自下方变暖的地球的热量。 着加剧了温室效应。 高层云朵使得全球变暖变得更糟。
Clouds are moving in other dimensions, too. The atmospheric circulation, that large-scale motion of air and water in the atmosphere, is changing, and clouds are going with it. On large scales, clouds seem to be moving from the tropics toward the poles. It's kind of like your grandparents in reverse. And this matters, because if your job is to block incoming sunlight, you are going to be much more effective in the tropics under that intense tropical sun than you are in higher latitudes. So if this keeps up, this will also make global warming worse. And what we have not found, despite years of looking, is any indication of the opposite. There is no observational evidence that clouds will substantially slow down global warming. The earth is not going to break its own fever.
云也在其他层面移动。 大气环流， 即大气中大范围的空气和水的移动， 在变化， 而且云随之而动。 大范围来看， 云看上去从赤道移向了两极。 这就像你祖父母在返老还童一样。 这很重要， 因为如果你的职责是挡住过来的太阳光， 挡住赤道那强烈的阳光 要比在高纬度 更加有效。 如果这种情况持续， 全球变暖也会加剧。 尽管有多年的观测， 我们仍没发现， 任何相反的迹象。 没有观测证据显示 云可以显著的降低全球变暖的速度。 地球不能自己治愈发热。
Now, there are still uncertainties here. We don't know for sure what the future holds. But we are sending our kids there, and they are never coming back. I want them to be prepared for what they'll face, and that is why it is so important to keep our earth-observing satellites up there and to hire diverse and smart and talented people who do not hate clouds to improve the climate models.
现在，仍然存在不确定性。 我们不准确知道 未来会怎么样。 但是我们把我们的孩子送往那里， 他们永远不会回来。 我想让他们为他们将要面对的做好准备， 这就是为什么让我们的地球观测卫星 继续在太空运作， 以及雇用不同的、聪明的、有才能的、 而且不讨厌云的人，来改进气候模型 十分重要的原因。
But uncertainty is not ignorance. We don't know everything, but we don't know nothing, and we know what carbon dioxide does. I started my career as an astrophysicist, so you can believe me when I say that this is the greatest place in the universe. Other planets might have liquid water. On earth, we have whiskey.
但是不确定性不容忽视。 我们不知道所有事情， 但我们不是一无所知， 我们知道二氧化碳所做的。 我以天体物理学家作为职业起步， 所以你们可以相信我， 我说地球是宇宙中最棒的地方。 其他星球可能有液态水。 地球上，我们有威士忌。
(Laughter)
（笑声）
(Applause)
（掌声）
We are so lucky to live here, but let's not push our luck. I don't think that clouds will save the planet. I think that's probably up to us.
我们能居住于此太幸运了， 但让我们不要用尽好运。 我不认为云会拯救地球。 我认为那取决于我们。
Thank you.
谢谢。
(Applause)
（掌声）