So, I'm a climate scientist, and if this room is representative of the country we live in,
我是一位气候科学家，如果这个房间代表我们所处的国家，
that means about 60 percent of you, so maybe from about there over,
那么大约你们中的60%，差不多从那里一直到我的右边，
don't strongly trust me for information on the causes of climate change.
不相信我在气候变化上的观点。
Now, I promise to tell the truth tonight, but just to humor that demographic, I've started this talk with a falsehood.
我保证今晚说的都是真话，但是为了那些不相信我的人，我会从一句假话谈起。
This statement was not made by President Obama.
这话不是奥巴马总统说的。
It was made by President Reagan, and it wasn't about climate change and the Paris Climate Accord.
是里根总统说的，而且它不是关于气候变化和巴黎气候协定的。
It was actually about the Montreal Protocol and stratospheric ozone depletion.
它其实是关于蒙提利尔协定和平流层臭氧损耗的。
Now, I'm sure that many of you aren't familiar with this environmental problem,
我很确定你们当中很多人不太熟悉臭氧层问题，
but you should be, because it's a rare environmental success story.
但你们应该熟悉，因为这是一个很罕见的成功的环保案例。
And it's worth revisiting, because sometimes,
这值得我们从中学习，因为有时，
we need to examine the world we've avoided in order to find guidance for the choices we make today.
我们需要从所避免的环境灾难中学习，才能更好地做出当下的选择。
So let's go back to the 1970s, when some questionable choices were made: first of all -- hoo -- hairstyles.
让我们回到20世纪70年代，在那个时代，人们做出了一些不当的选择：首先是发胶。
Second of all, objectively terrible quantities of hairspray,
其次，客观地说，质量糟糕的喷发定型剂，
and third, CFCs, chlorofluorocarbons, man-made chemicals that were used as propellant in aerosol spray cans.
第三，CFC，也就是氯氟烃，CFC是人造的化学品，被用作喷雾剂中的压缩气体。
And see, it turns out these CFCs were a problem because they were destroying the ozone layer.
后来，人们发现CFC引发了一个问题，因为它会破坏臭氧层。
Now I'm sure most of you have heard of the ozone layer, but why does it matter?
我很确定大多数人都听说过臭氧层，为什么我们要在意臭氧层呢？
Well, quite simply, the ozone layer is earth's sunscreen, and it's really fragile.
简单来说，臭氧层是地球的防晒霜，而且它十分脆弱。
If you could take all of the ozone, which is mostly about 10 to 20 miles up above our heads,
臭氧大多都处于地面以上20至25公里处，若你取得地球上所有臭氧，
and compress it down to the surface of the earth,
然后把它们压缩在地球表面，
it would form a thin shell only about two pennies thick, about an eighth of an inch.
它会形成大概有两个分币厚的薄层，大概3毫米厚。
And that thin shell does an amazing amount of work, though.
而这薄薄一层臭氧其实十分重要。
It filters out more than 90 percent of the harmful UV radiation coming from the sun.
它能抵御超过90%源自太阳的有害紫外线辐射。
And while I'm sure many of you enjoy that suntan that you get from the remaining 10 percent,
虽然我知道很多人都喜欢晒太阳，但即使是剩下10%的紫外线辐射
it causes a lot of problems: cataracts, damage to crops, damage to immune systems and also skin cancer.
也能造成很多麻烦：如白内障，损害农作物，损伤免疫系统以及皮肤癌。
It's not an exaggeration to say that a threat to the ozone layer is a threat to human safety.
对臭氧层的威胁就是对人类安全的威胁，并不是夸大其词。
And actually, ironically, it was human safety that motivated the invention of CFCs in the first place.
讽刺的是，正是处于对人类安全的担忧，促成了氟利昂的发明。
You see, in the early days of refrigeration, refrigerators used toxic and flammable chemicals like propane and ammonia.
在电冰箱刚刚投入使用时，会使用有毒，易燃的化学品，如丙烷和氨。
For good reason, the refrigeration industry wanted a safe alternative, and they found that in 1928,
所以制冷工业想要一个更安全的替代物，他们在1928年找到了它，
when a scientist named Thomas Midgley synthesized the first commercially viable CFCs.
一位叫做Thomas Midgley的科学家率先合成了商业上可用的CFC。
And in fact, Midgley famously inhaled CFCs and blew out a candle to demonstrate, at a scientific conference,
事实上，Midgley在一场学术论坛上亲自吸入了CFC并用其吹灭了一支蜡烛，
that they were safe and nonflammable.
来证明CFC十分安全并不易燃。
And in fact, as a scientist, I can tell you there is no way you could get away with that kind of antic today. I mean, wow.
其实，作为一名科学家，我可以告诉你，现在你可没办法像他这样演示。真的，这让人感觉不可思议。
But really, at the time, CFCs were a really remarkable invention.
而在那时，CFC是一项十分卓越的发明。
They allowed what we now know as modern-day refrigeration and air-conditioning and other things.
它促成了当代的制冷技术，还有空调等等。
So it wasn't actually until over 40 years later, in the 1970s,
直到四十年之后的1970年代，
when scientists realized that CFCs would break down high in the atmosphere and damage the ozone layer.
科学家们才意识到CFC会在大气层的高处降解，破坏臭氧层。
And this finding really set off a lot of public concern.
这个发现引发了公众的担忧。
It led, ultimately, to the banning of CFC usage in aerosol spray cans in the US and a few other countries in 1978.
最后在1978年，美国和一些其他国家禁止在喷雾剂中使用CFC。
Now, the story doesn't end there, because CFCs were used in much more than just spray cans.
而故事可没在那时结束，因为CFC不止被用在喷雾剂中。
In 1985, scientists discovered the Antarctic ozone hole, and this was a truly alarming discovery.
在1985年，科学家发现了南极上空的臭氧层空洞，这是一项十分让人警醒的发现。
Scientists did not expect this at all.
科学家们完全没有预料到。
Before the Antarctic ozone hole, scientists expected maybe a five or 10 percent reduction in ozone over a century.
在此前，科学家们预期一个世纪中大概会有5%至10%的臭氧衰减。
But what they found over the course of less than a decade was that more than a third of the ozone had simply vanished,
但他们发现，在不到十年中，在面积超过美国的地区上方，
over an area larger than the size of the US.
超过三分之一的臭氧消失了。

And although we now know that CFCs are the root cause of this ozone hole, at the time, the science was far from settled.
虽然我们现在知道CFC是臭氧层空洞的祸根，当时学术上还远远没有定论。
Yet despite this uncertainty, the crisis helped spur nations to act.
而尽管有这样的不确定性，那场危机却得以促使各个国家采取行动。
So that quote that I started this talk with, about the Montreal Protocol, from President Reagan
回到我开始时引用里根总统关于蒙特利尔协定的那句话，
that was his signing statement when he signed the Montreal Protocol after its unanimous ratification by the US Senate.
那是美国参议院一致通过之后，里根总统签订协议时候的声明。
And this is something that's truly worth celebrating.
这是一件真正值得庆祝的事。
In fact, yesterday was the 30th anniversary of the Montreal Protocol.
其实，昨天就是蒙特利尔协定签订的三十周年。
Because of the protocol, ozone-depleting substances are now declining in our atmosphere,
因为这项协定，大气层中侵害臭氧的物质正在减少，
and we're starting to see the first signs of healing in the ozone layer.
而我们也已经看到了臭氧层恢复的初步征兆。
And furthermore, because many of those ozone-depleting substances are also very potent greenhouse gases,
而且，因为很多侵害臭氧的物质同时也是强力的温室气体，
the Montreal Protocol has actually delayed global warming by more than a decade. That's just wonderful.
蒙特利尔协定将全球变暖的发生推迟了十年。那太棒了。
But I think it's worth asking the question, as we face our current environmental crisis, global warming,
但我觉得我们应该思索这个问题，特别是当我们面对当下全球变暖的环境问题时，
what lessons can we learn from Montreal? Are there any? I think there are.
我们可以从蒙特利尔协定中学到什么？有值得借鉴之处吗？我觉得有。
First, we don't need absolute certainty to act.
首先，我们并不需要百分之百确定才采取行动。
When Montreal was signed, we were less certain then of the risks from CFCs than we are now of the risks from greenhouse gas emissions.
当蒙特利尔协定签订时，我们对于CFC的危害远不如我们现在对温室气体的危害来的确定。
A common tactic that people who oppose climate action use is to completely ignore risk and focus only on uncertainty.
有些反对针对气候变化采取行动的人常用的说辞就是无视风险而单单强调不确定性。
But so what about uncertainty? We make decisions in the face of uncertainty all the time, literally all the time.
不确定又如何呢？我们每时每刻都在面对不确定性。真的，每时每刻。
You know, I'll bet those of you who drove here tonight, you probably wore your seat belt.
我想你们很多人都是开车来这里的，你们大概系了安全带。
And so ask yourself, did you wear your seat belt because someone told you
请想一下，你系安全带是因为有人告诉你，
with a hundred percent that you would get in a car crash on the way here?
你有百分之百的可能会在来这儿的路上出车祸吗？
Probably not. So that's the first lesson.
大概不是。所以这就是我们学到的第一件事。
Risk management and decision making always have uncertainty.
风险管理和决策制定永远都伴随着不确定性。
Ignoring risk and focusing only on uncertainty is a distraction. In other words, inaction is an action.
忽视风险而专注于不确定性只会分散我们的注意力。换句话说，不做选择也是一种选择。
Second, it takes a village to raise a healthy environment.
第二，创造健康的环境需要来自多方的努力。
The Montreal Protocol wasn't just put together by industry and governments or environmental advocacy groups and scientists.
蒙特利尔协定不仅仅是由行业机构和政府或是环保活动家和科学家单独制定的。
It was put together by all of them.
而是由他们所有人一起制定的。
They all had a seat at the table, and they all played an important role in the solution.
他们都有所参与，都在解决臭氧层问题中发挥了重要作用。
And I think in this regard, we're actually seeing some encouraging signs today.
我想在这个方面，我们在今天也做得很好。
We see not just environmental groups concerned about climate change but also civic and religious groups, the military and businesses.
我们不仅看到环保组织致力于对抗气候变化，还有公民运动和宗教组织，军事组织和商业组织。
So wherever you find yourself on that spectrum, we need you at the table,
所以不管你是谁，我们需要你的参与，
because if we're going to solve global warming, it's going to take actions at all levels,
因为解决全球变暖需要各个层面的行动，从个人到国际，
from the individual to the international and everything in between.
还有两者之间的每个层面。
Third lesson: don't let the perfect be the enemy of the good.
第三点：不要拘泥于完美而止步不前。
While Montreal has become the brake pedal for stopping ozone depletion,
虽然蒙特利尔协定最终成为了臭氧损耗的休止符，
at its beginning, it was more just like a tap on the brakes.
在最开始，它的效果并不明显。
It was actually the later amendments to the protocol that really marked the decision to hit the brakes on ozone depletion.
其实是之后对协定的修正真正阻止了臭氧损耗。
So to those who despair that the Paris Climate Accord didn't go far enough
所以对那些悲观主义者，他们觉得巴黎气候协定做的远远不够，
or that your limited actions on their own won't solve global warming,
或是一个人的努力解决不了全球变暖，
I say don't let the perfect be the enemy of the good.
我会说，不要拘泥于完美而止步不前。
And finally, I think it helps us to contemplate the world we've avoided.
最后，我想这有助于我反思所避免的危害。
Indeed, the world we have avoided by enacting the Montreal Protocol is one of catastrophic changes to our environment and to human well-being.
的确，我们通过蒙特利尔协定避免的是对环境和人类的灾难性的变化。
By the 2030s, we'll be avoiding millions of new skin cancer cases per year with a number that would only grow.
到2030年，我们会避免每年数以百万计的皮肤癌病例，这个数字只会增长。
If I'm lucky, I'll live long enough to see the end of this animation and to see the ozone hole restored to its natural state.
如果我够幸运，就能够见证这场变化的结尾，看到臭氧层恢复到它原初的状态。
So as we write the story for earth's climate future for this century and beyond, we need to ask ourselves,
所以，当我们在这个世纪以及未来书写地球气候的历史时，我们要问自己，
what will our actions be so that someone can stand on this stage in 30 or 50 or a hundred years
我们要做什么才能让30、50或者100年后，有人能够站在这个舞台上，
to celebrate the world that they've avoided. Thank you.
庆祝他们避免的种种灾害。谢谢。