宇宙时空之旅（2014）

Cosmos: A SpaceTime Odyssey S01E12

Part 2 April 25, 2021, 12:41 p.m.

但他也发现了一个令人震惊的事实
But he also discovered something shocking--
有一个数字以人类历史上前所未有的速度增长
a rapid rise, unprecedented in human history,
那就是二氧化碳的总含量
in the overall level of CO2,
至今这个趋势仍在继续
one that has continued ever since.
二氧化碳含量已经远远超过了
It's a striking departure from the CO2 levels that prevailed
农业和文明兴起阶段的水平
during the rise of agriculture and civilization.
实际上地球三百万年以来
In fact, the Earth has seen nothing like it
从未有过这样的经历
for three million years.
我们为何能如此肯定
How can we be so sure?
证据就蕴含在水中
The evidence is written in water.
地球一直用过往年份降下的雪
The Earth keeps a detailed diary
保存着详尽的记录
written in the snows of yesteryear.
气候学家从格陵兰和南极洲的
Climate scientists have drilled ice cores
冰川深处钻出冰芯
from the depths of glaciers in Greenland and Antarctica.
远古空气被困在冰层中
The ice layers have ancient air trapped inside them.
我们能读到地球大气的完整记录
We can read the unbroken record of Earth's atmosphere
一直可追溯至80万年前
that extends back over the last 800,000 years.
在过去的所有时间里
In all that time,
大气中的二氧化碳含量从未超过
the amount of carbon dioxide in the air never rose
百万分之三
above three-hundredths of one percent.
直到二十世纪才有了变化
That is, until the turn of the 20th century.
从那以后它就开始稳定而迅速地增长
And it's been going up steadily and rapidly ever since.
现在这个数字比工业革命之前
It's now more than 40% higher
高出了40%
than before the Industrial Revolution.
通过燃烧煤石油和天然气
By burning coal, oil and gas,
人类文明在不断排放二氧化碳
our civilization is exhaling carbon dioxide
排放的速度远超过了地球能吸收的速度
much faster than Earth can absorb it.
二氧化碳就在大气中不断累积
So CO2 is building up in the atmosphere.
整个星球都在升温
The planet is heating up.
所有发热的物体都在发出一种
Every warm object radiates a kind of light
我们用肉眼看不见的光线
we can't see with the naked eye--
红外线
thermal infrared light.
我们都在向外发出热辐射即使身处黑暗
We all glow with invisible heat radiation, even in the dark.
这就是红外线下的地球
This is what the Earth looks like in the infrared.
你可以看见地球本身的热量
You're seeing the planet's own body heat.
太阳发出的光到达地球表面
Incoming light from the Sun hits the surface.
地球本身吸收了大部分能量
The Earth absorbs much of that energy,
使地球升温
which heats the planet up
也使地表发出红外线
and makes the surface glow in infrared light.
但大气中的二氧化碳
But the carbon dioxide in the atmosphere
吸收了散发出的大部分热量
absorbs most of that outgoing heat radiation,
将大部分热量传送回地表
sending much of it right back to the surface.
这就使地球更加温暖
This makes the planet even warmer.
这就是所谓的温室效应
That's all there is to the greenhouse effect.
它的基本原理
It's basic physics,
就是使能量留存下来
just bookkeeping of the energy flow.
这一点是毫无争议的
There's nothing controversial about it.
如果大气中没有任何二氧化碳
If we didn't have any carbon dioxide in our atmosphere,
地球就会变成一个大雪球
the Earth would just be a great big snowball,
我们人类也不会存在
and we wouldn't be here.
所以适度的温室效应是件好事
So, a little greenhouse effect is a good thing.
但严重的温室效应会使气候失常
But a big one can destabilize the climate
毁掉我们的生活
and wreck our way of life.
好吧但我们怎么知道自己就是问题所在
All right... but how do we know that we're the problem?
也许二氧化碳含量升高是地球本身造成的
Maybe the Earth itself is causing the rise in CO2.
也许这与我们燃烧煤和石油毫无关系
Maybe it has nothing to do with the coal and oil we burn.
也许是因为那些该死的火山
Maybe it's those damn volcanoes.
每过几年西西里岛的埃特纳火山就会喷发
Every few years, Mount Etna, in Sicily, blows its stack.
每次大型喷发都会把百万吨♥二氧化碳
Each big eruption sends millions of tons of CO2
排放到大气中
into the atmosphere.
现在如果把它与
Now, combine that with the output
地球上所有其他的火山活动都加在一起
of all the other volcanic activity on the planet.
我们就按估计值的最大值算
Let's take the largest scientific estimate--
每年火山大概会把五亿吨♥二氧化碳
about 500 million tons of volcanic CO2
排放到大气中
entering the atmosphere ever year.
听起来可真不少是不是
Sounds like a lot, right?
但这几乎还达不到人类每年产生的百分之二
But that's not even two percent of the 30 billion tons of CO2
也就是每年三百亿吨♥二氧化碳
that our civilization is cranking out every year.
而且有趣的是
And, funny thing,
测量出的大气中二氧化碳的增量
the measured increase in CO2 in the atmosphere
与已知的燃烧煤石油和天然气排放量
tallies with the known amount we're dumping there
刚好吻合
by burning coal, oil and gas.
火山喷发排放的二氧化碳有一个明显特征
Volcanic CO2 has a distinct signature--
它比燃烧化石燃料排放的
it's slightly heavier than the kind produced
要稍重一些
by burning fossil fuels.
当我们在原子层面检测时
We can tell the difference between the two
我们可以分辨出两者的区别
when we examine them at the atomic level.
很明显大气中增长的二氧化碳
It's clear that the increased CO2 in the air
并非来自火山
is not from volcanoes.
还有人们观测到的地球变暖程度
What's more, the observed warming is as much as predicted
与二氧化碳的增幅几乎同步
from the measured increase in carbon dioxide.
这二者紧密相关
It's a pretty tight case.
证据充足我们无法开脱
Our fingerprints are all over this one.
每年排放三百亿吨♥二氧化碳是什么概念
How much is 30 billion tons of CO2 per year?
如果你把它压成固体
If you compressed it into solid form,
它的体积将与
it would occupy about the same volume
多佛白崖差不多
as the White Cliffs of Dover.
而且我们每年都向大气中排放这么多二氧化碳
And we're adding that much CO2 to the air every year,
无休止地年复一年地
relentlessly, year after year.
不幸的是人类文明产生的
Unlucky for us, the main waste product
主要废弃物不是其他的什么物质
of our civilization is not just any substance.
这种气体恰恰是年复一年
It happens to be the chief climate-regulating gas
保持地球气候稳定的主要成分
of our global thermostat, year in, year out.
二氧化碳是一种看不见的气体真是糟糕
Too bad CO2 is an invisible gas.
如果我们能看见它...
Maybe if we could see it...
如果我们的眼睛能感受到二氧化碳
If our eyes were sensitive to CO2--
也许宇宙中真的存在这种生物
and perhaps there are such beings in the cosmos--
如果我们看见所有的二氧化碳
if we could see all that carbon dioxide,
那样我们就不会再否认
then we would overcome the denial
而是理解我们对于大气的严重影响
and grasp the magnitude of our impact on the atmosphere.
但全球变暖的证据
But the evidence that the world is getting warmer
就在我们身边
is all around us.
首先我们来检查一下温度计
For starters, let's just check the thermometers.
全世界的气象站
Weather stations around the world
自十九世纪八十年代起
have been keeping reliable temperature records
就开始记录可靠的温度数据
since the 1880s,
美国航♥天♥局用这些数据
and NASA has used the data to compile a map
编制了一份不同年份中
tracking the average temperatures
地球平均气温的地图
around the world through time.
黄色表示对于这一地区
Yellow means warmer temperatures
气温高于十九世纪八十年代水平
than the average, for any region in the 1880s.
橙色表示炎热
Orange means hot.
红色表示更热
And red means hotter.
世界比它在十九世纪时更暖了
The world is warmer than it was in the 19th century.
当年在全球最伟大的世界博览会上
Back then, at the greatest fair the world has ever seen,
一个被遗忘的天才找到了问题的解决方法
a forgotten genius demonstrated the solution to this problem.
跟我来
Come with me.
曾经存在过这样一个世界
Once there was a world
既不太炎热也不太寒冷
that was not too hot and not too cold.
气温适中
It was just right.
接下来上面繁衍的生命
Then there came a time when the life it sustained
开始注意到可爱的地球起了变化
began to notice our lovely planet was changing.
这并不意味着我们未曾预见到它的出现
And it's not as if we didn't see it coming.
早在1♥8♥9♥6年
As far back as 1♥8♥9♥6,
瑞典科学家斯凡特·阿伦尼斯
the Swedish scientist Svante Arrhenius
《空气中的碳酸将影响地表温度》
计算出如果大气中二氧化碳的量翻倍
calculated that doubling the amount of CO2 in the atmosphere
大气的作用就好像温室的玻璃
北极的冰就会融化
would melt the Arctic ice.
在二十世纪三十年代
In the 1930s,
美国物理学家E. O. 赫尔伯特
the American physicist E. O. Hulburt,