What if there was a way to build a thermostat that allowed you to turn down the temperature of the earth anytime you wanted?
是否可以创造一个恒温器，能在任何时候给地球降温？
Now, you would think if somebody had a plausible idea about how to do that,
你也许会认为，如果有人已经找到了可行的方法，
everybody would be very excited about it, and there would be lots of research on how to do it.
每个人都会非常激动，而且关于这方面的研究也会有很多。
But in fact, a lot of people do understand how to do that.
事实是，许多人明白如何做。
But there's not much support for research in this area.
但是，这些方法并没有得到相关研究的支持。
And I think part of it is because there are some real misunderstandings about it.
我认为，其中部分原因是人们对这项研究存在着误解。
So I'm not going to try to convince you today that this is a good idea.
今天，我不会说服大家承认我要说的是一个好办法。
But I am going to try to get your curiosity going about it and clear up some of the misunderstandings.
但我会尝试让你们对治理气候变化感兴趣，并消除其中一些误解。
So, the basic idea of solar geoengineering is that
太阳能地球工程的基本思想就是，
we can cool things down just by reflecting a little bit more sunlight back into space.
我们通过把一部分阳光反射回太空的方式，给地表的物体降温。
And ideas about how to do this have been around literally for decades.
数十年来人们都在讨论如何实现这种想法。
Clouds are a great way to do that, these low-lying clouds.
低空的云就是一种很棒的方式。
Everybody knows it's cooler under a cloud.
人们都知道云底下凉快。
I like this cloud because it has exactly the same water content as the transparent air around it.
我喜欢这种云是因为它的含水量和周围的空气一致。
And it just shows that even a little bit of a change in the flow of the air can cause a cloud to form.
这就意味着，只要空气的流动发生一点改变，就能形成云。
We make artificial clouds all the time.
我们经常在空中制造人造云。
These are contrails, which are artificial water clouds that are made by the passing of a jet engine.
这些云是飞机飞行痕迹，是人造水云，是由喷气式发动机产生的。
And so, we're already changing the clouds on earth. By accident.
我们已经在不经意间改变地球上的云了。
Or, if you like to believe it, by supersecret government conspiracy.
或者，你可能更愿意认为这是政府的绝密阴谋。
But we are already doing this quite a lot. This is a NASA picture of shipping lanes.
我们在这方面已经做了很多工作。这是一张由NASA拍摄的船舶航线图。
Passing ships actually cause clouds to form,
船舶的航行会导致云的形成，
and this is a big enough effect that it actually helps reduce global warming already by about a degree.
而且这种影响效应非常大，大到能让大气温度降低一度，从而减缓了全球变暖效应。
So we already are doing solar engineering. There's lots of ideas about how to do this.
也就是说，我们已经开始研究太阳能工程了。有很多关于实现这一工程的想法。
People have looked at everything, from building giant parasols out into space to fizzing bubble waters in the ocean.
人们着眼于方方面面，从在太空建造巨大的遮阳伞，到在海洋里产生气泡。
And some of these are actually very plausible ideas.
其中有一部分想法是十分可行的。
One that was published recently by David Keith at Harvard is to take chalk and put dust up into the stratosphere,
最近，哈佛的大卫·凯斯提出了一个想法，将白垩粉（如粉笔灰）洒到平流层中，
where it reflects off sunlight. And that's a really neat idea,
用来反射太阳光。这确实是一个不错的注意，
because chalk is one of the most common minerals on earth, and it's very safe -- it's so safe, we put it into baby food.
因为白垩是地球上最常见的矿物之一，而且非常安全--安全到可以添加到婴儿的食物中。
And basically, if you throw chalk up into the stratosphere,
如果你把白垩投入到平流层中，
it comes down in a couple of years all by itself, dissolved in rainwater.
它会花几年的时间才落到地面，并溶解在雨水中。
Now, before you start worrying about all this chalk in your rainwater, let me explain to you how little of it it actually takes.
在你担心雨水中的白垩之前，我先向你们解释一下，我们使用的白垩是有多么的少。
And that turns out to be very easy to calculate. This is a back-of-the-envelope calculation I made.
可以证明它的用量非常容易计算。这是我粗略的计算。

I assure you, people have done much more careful calculations, and it comes out with the same answer,
我可以向各位保证，已经有人进行过更详细的计算，得出的结果是一致的，
which is that you have to put chalk up at the rate of about 10 teragrams a year to undo the effects of the CO2 that we've already done
你需要每年以10太克（1Tg=10^9公斤）的速率向平流层投放白垩，来消除二氧化碳的影响，这是我们已经在做的，
just in terms of temperature, not all the effects, but the temperature. So what does that look like?
仅仅是温度方面的影响，不包含其他的影响。那么这个数字是什么概念？
I can't visualize 10 teragrams per year. So I asked the Cambridge Fire Department and Taylor Milsal to lend me a hand.
我想象不出每年10太克是什么样子的。所以，我请了剑桥消防部门，以及泰勒·米尔索帮我一个忙。
This is a hose pumping water at 10 teragrams a year.
这根水管的出水量就是一年10太克。
And that is how much you would have to pump into the stratosphere to cool the earth back down to pre-industrial levels.
这个规模就是让地球降温到工业时代前的水平，需要将白垩注入到平流层的量。
And it's amazingly little; it's like one hose for the entire earth.
这个量小得惊人，整个地球只需要这一根水管就够了。
Now of course, you wouldn't really use a hose, you'd fly it up in airplanes or something like that.
当然，你不必使用一根水管，可以通过飞机或其他类似的方法将白垩带上去。
But it's so little, it would be like putting a handful of chalk into every Olympic swimming pool full of rain. It's almost nothing.
这个量非常的小，就好像用手抓一把白垩放入与奥运会标准泳池等量的雨水中。很难察觉出变化。
So why don't people like this idea? Why isn't it taken more seriously?
那么为什么人们不喜欢这种方法？为什么不重视这种方法？
And there are some very good reasons for that.
有一些很好的理由。
A lot of people really don't think we should be talking about this at all.
有很多人不认为我们应当去研究这种方法。
And, in fact, I have some very good friends in the audience who I respect a lot,
事实上，在座的观众中有一些是我非常要好的朋友，我非常尊敬他们，
who really don't think I should be talking about this.
他们认为我不应该研究这个。
And the reason is that they're concerned that if people imagine there's some easy way out,
因为他们关心的是，人们是否还能想出更简单的办法
that we won't give up our addiction to fossil fuels. And I do worry about that.
来摆脱对化石燃料的依赖。我也关心这一点。
I think it's actually a serious problem. But there's also, I think, a deeper problem, which is:
因为我认为这是一个很严重的问题，也是一个很深奥的问题，
nobody likes the idea of messing with the entire earth -- I certainly don't.
没有人喜欢让整个地球陷入混乱的想法，我当然也不喜欢。
I love this planet, I really do. And I don't want to mess with it.
我喜欢这个星球，说真的，我不想给地球制造任何麻烦。
But we're already changing our atmosphere, we're already messing with it.
但是我们已经在改变我们的大气层了，我们已经把它搞得乌烟瘴气了。
And so I think it makes sense for us to look for ways to mitigate that impact.
所以我们应该寻找一些方法减缓大气变化造成的影响。
And we need to do research to do that. We need to understand the science behind that.
这就意味着我们需要去研究它，我们需要弄清楚这背后的科学道理。
I've noticed that there's a theme that's kind of developed at TED,
我注意到，在TED中有关于发展的主题，
which is kind of, "fear versus hope," or "creativity versus caution."
类似于“恐惧与希望”，或者是“创造与谨慎”。
And of course, we need both of those. So there aren't any silver bullets. This is certainly not a silver bullet.
当然，我们也需要这些思想。但这不是完美的解决办法，这确实不是完美的解决办法。
But we need science to tell us what our options are; that informs both our creativity and our caution.
但我们需要通过科学知道我们有哪些选择；这会为我们的创造力和谨慎态度带来指导。
So I am an optimist about our future selves, but I'm not an optimist because I think our problems are small.
对人类的未来，我是一个乐观主义者，我乐观的原因并不是因为这些问题很小。
I'm an optimist because I think our capacity to deal with our problems is much greater than we imagine. Thank you very much.
而是因为我认为我们有能力解决这些问题，而且方法比我们想象的要好。非常感谢。
This talk sparked a lot of controversy at TED2017, and we encourage you to look at discussions online to see other points of view.
这场演讲在TED2017引起了许多议论，我们鼓励观众们上网了解这些讨论，了解其他的观点。