宇宙时空之旅（2014）

Cosmos: A SpaceTime Odyssey S01E12

Part 3 April 25, 2021, 12:41 p.m.

在海军实验室里
at the Naval Research Laboratory,
证实了这一结果
confirmed that result.
二氧化碳使地球升温
截至到那时这些都仍然只是理论
So far, it was still just theoretical.
《论人类活动产生的二氧化碳及其对气温的影响》
但随后英国工程师盖伊·卡伦德
But then, the English engineer Guy Callendar
搜集整理了
assembled the evidence to show
二氧化碳和全球平均气温
that both the CO2 and the average global temperature
确实都在上升的证据
were actually increasing.
即使现在人们也可能通过文明排放的废物
Even now, man may be unwittingly changing the world's climate
弗兰克·百特博士 1958《天空之上:挣脱束缚的神》
无意间改变了全球气候
through the waste products of his civilization.
人类每年通过工厂和
Due to our release, through factories
汽车排放大量废气
and automobiles every year, of more than
含有超过六十亿吨♥二氧化碳
six billion tons of carbon dioxide,
这有助于大气从阳光中吸热
which helps air absorb heat from the Sun,
我们的大气似乎越来越暖
our atmosphere seems to be getting warmer.
这是坏事吗
This is bad?
计算表明如果地球的温度
Well, it's been calculated, a few degrees rise
升高几度
in the Earth's temperature
会使两极冰盖融化
would melt the polar ice caps.
1960年卡尔·萨根的博士论文中
In 1960, Carl Sagan's PhD thesis
首次写到
included the first calculation
金星上失控的温室效应的计算
of the runaway greenhouse effect on Venus.
这是他毕生兴趣的一部分
This was part of a career-long interest
长♥期♥致力于研究行星大气也包括地球大气
in the atmospheres of the planets, including our own.
在1980年版《宇宙》中
In the original Cosmos series, in 1980,
卡尔·萨根提出警告
Carl Sagan warned...
我们正在排放大量二氧化碳
We are releasing vast quantities of carbon dioxide,
加剧了温室效应
increasing the greenhouse effect.
用不了多久
It may not take much
地球气候就会失稳
to destabilize the Earth's climate,
这会把这个天堂我们在宇宙中的唯一家园
to convert this heaven, our only home in the cosmos,
变为地狱
into a kind of hell.
卡尔说完这些话之后
Since Carl spoke those words,
我们还在继续加重大气的负担
we've burdened the atmosphere of our world with an additional
又排放了四千亿吨♥二氧化碳
400 billion tons of carbon dioxide.
如果我们不改变生产方式
If we don't change our ways,
我们的子孙将会面对一个什么样的地球
what will the planet be like in our children's future?
根据科研结果
Based on scientific projections,
如果我们保持现有的经济模式不变
if we just keep on doing business as usual,
我们子孙的未来不容乐观
our kids are in for a rough ride.
致命的热浪空前的干旱
Killer heat waves, record droughts,
海平面升高大量物种灭绝
rising sea levels, mass extinction of species.
从祖先那里我们继承了一个富饶的世界
We inherited a bountiful world
它因相对温和的气候而存在
made possible by a relatively stable climate.
农业和文明繁荣发展
Agriculture and civilization flourished
延续数千年
for thousands of years.
但是现在我们的大意和贪婪
And now, our carelessness and greed
将这一切置于险境
put all of that at risk.
好如果我们的科学家是如此出色
Okay, so if we scientists are so good
能作出这些可怕的关于气候的长远预测
at making these dire, long-term predictions about the climate,
那为什么预测天气就这么差劲呢
how come we're so lousy about predicting the weather?
再说了今年我们镇冬天特别寒冷
Besides, this year, we had a colder winter in my town.
我们这些科学家知不知道
For all us scientists know,
全球可能正在变冷
we could be in for global cooling.
这就是天气与气候的差别
Here's the difference between weather and climate...
天气是短期内的大气状态变化
Weather is what the atmosphere does in the short term--
每小时的每天的
hour to hour, day to day.
天气是复杂多变的也就意味着
Weather is chaotic, which means that even
即使是微小的干扰也会引起大规模的变化
a microscopic disturbance can lead to large-scale changes.
这就是为什么十天天气预报几乎没用
That's why those ten-day weather forecasts are useless.
在巴厘岛上有只蝴蝶扇动翅膀六周后
A butterfly flaps its wings in Bali, and six weeks later,
坏天气就毁掉了你在缅因州的户外婚礼
your outdoor wedding in Maine is ruined.
气候是天气长♥期♥的平均状态跨越多年
Climate is the long-term average of the weather, over a number of years.
它是由这个星球上能改变大气能量平衡的
It's shaped by global forces that alter the energy balance
力量决定的比如日照的变化
in the atmosphere, such as changes in the Sun,
地轴倾角的变化
the tilt of the Earth's axis,
地球反射回太空的太阳光
the amount of sunlight the Earth reflects back to space
还有大气中温室气体的浓度
and the concentration of greenhouse gases in the air.
以上任意一个因素变化都可以影响气候
A change in any of them affects the climate
而且我们基本可以预测它们的变化方式
in ways that are broadly predictable.
我的这位朋友在左摇右摆地散步
My friend's meandering
好比是短期的波动
represents the short-term fluctuations--
也就是天气
that's weather.
人们几乎不可能预测
It's almost impossible to predict
他下一秒被什么东西所吸引
what'll attract his interest next,
但我们不难得知他前进的大体方向
but not hard to know what the range of his meandering will be,
因为我用皮带拴着他
because I'm holding him on a leash.
我们无法直接观测气候
We can't observe climate directly--
我们所见皆是天气
all we see is the weather--
但天气的平均值经过几年的积累
but the average weather, over the course of years,
会体现出某种模式
reveals a pattern.
我就好比是这个长♥期♥趋势
I represent that long-term trend,
也就是气候
which is climate.
把注意力放在人上别放在狗上
Keep your eye on the man, not the dog.
天气难以预测就像我的这位朋友
Weather is hard to predict, like my friend here,
但气候是可以预知的
but climate is predictable.
在地球漫长的历史中气候曾有过多次变迁
Climate has changed many times in the long history of the Earth
每一次都是某种全球性力量的结果
but always in response to a global force.
目前影响气候变化的最强的力量
The strongest force driving climate change right now
就是因燃烧化石燃料而不断增加的二氧化碳
is the increasing CO2 from the burning of fossil fuels,
这使大气保留住更多阳光的热量
which is trapping more heat from the Sun.
这些多余的能量必须有个去处
All that additional energy has to go somewhere.
其中一部分加热空气
Some of it warms the air.
但大多数都被海洋吸收
Most of it ends up in the oceans.
全世界的海洋都在变暖
All over the world, the oceans are getting warmer.
最明显的例子在北冰洋
It's most obvious in the Arctic Ocean
以及环绕北冰洋的陆地
and the lands that surround it.
就算某个人迹罕至的地方
Okay, so we're losing the summer sea ice
少了一块夏季海冰又如何
in a place where hardly anyone ever goes.
北极有没有冰关我什么事呢
What do I care if there's no ice around the North Pole?
冰是地球最亮的自然表面
Ice is the brightest natural surface on the Earth,
开阔的海域则是最暗的自然表面
and open ocean water is the darkest.
冰可以将阳光反射回太空
Ice reflects incoming sunlight back to space.
水则会吸收阳光
Water absorbs sunlight
并受热变暖这会使更多冰融化
and gets warmer, which melts even more ice,
也就会露出更多海面
which exposes still more ocean surface
来吸收更多阳光
to absorb even more sunlight.
我们把这种现象称为正反馈循环
This is what we call a positive feedback loop.
这是能把二氧化碳引起的热效应放大的
It's one of many natural mechanisms that magnify
诸多自然机制中的一个
any warming caused by CO2 alone.
我们在阿♥拉♥斯加的德鲁角
We're at Drew Point, Alaska,
地处北冰洋的边缘
on the edge of the Arctic Ocean.
我出生时
When I was born,
这里的海岸线比现在多伸出约1.6千米
the shoreline was a mile farther out,
它过去曾以每年6米多的速度回缩
and it was breaking off at a rate of about 20 feet per year.
而现在...
Now...
回缩的速度超过每年15米
it's being eaten away at about 50 feet per year.
北冰洋正在变暖
The Arctic Ocean is warming
而且是加速变暖
and at an increasing rate.
所以每年的无冰期延长了
So it's ice-free during more of the year.
有更多的海岸线
That leaves the shore here
因此暴露出来更易被风暴侵蚀
more exposed to erosion from storms,
这也让另一种力量变得更强大
which are also getting more powerful,
气候变化带来的另一种影响
another effect of climate change.
阿♥拉♥斯加西伯利亚加拿大的北部
The northern reaches of Alaska, Siberia and Canada
大部分都被永久冻土所覆盖
are mostly permafrost,
地面冻结超过千年
ground that has been frozen year-round for millennia.
这里面含有很多有机质
It contains lots of organic matter,
包括千年以前的
old leaves and roots from plants
旧叶与树根