打破边界：我们星球的科学（2021）

那就是你的界限？
And that becomes your boundary.
如果科学家能够定义我们星球的界限
If scientists could define our planet’s boundaries,
他们能不能也给我们路线图 引导我们摆脱目前的危机
could they also give us the road map to guide us out of our current crisis?
不仅向我们展示如何避免崩塌
To show us not only how to avoid collapse,
还有如何确保我们自己在地球上蓬勃发展的未来？
but how to secure our own thriving future on planet Earth?
我们大家都知道第一个也是最明显的界限
The first and most obvious boundary is well known to us all.
目前全球气温
With global temperatures now warmer
比文明诞生以来还要高
than they’ve been since the dawn of civilization,
眼下存在一种危险 我们已经越过了地球气候的界限
there is a danger that we have already crossed the boundary in Earth’s climate.
也许最令人震惊的证据
Perhaps the most alarming evidence of this
就是我们星球冰层的变化
is in the change of our planet’s ice.
身为瑞典人 约翰比大多数人更能深切地感受到这一点
As a Swede, Johan feels this more keenly than most.
身为瑞典儿童像所有的瑞典儿童一样
As a kid in Sweden, like all children in Sweden,
我们知道 凯布讷山的南峰是瑞典的最高峰
we learn that the south top at Kebnekaise is the highest peak in this country.
这正是作为瑞典公民
And it’s something that is just ingrained
一种根深蒂固的认同
in the identity of being a Swedish citizen.
因此 这令人黯然神伤
So, of course, it’s…
你知道
You know, with sadness,
人们逐渐意识到情况将会有所改变
one comes to realize that that will no longer be the case.
凯布讷山的南峰
The south peak of Kebnekaise
最近失去了瑞典最高峰的地位
has recently lost its status as the highest peak in Sweden.
在过去的50年里
The glacier that makes up its highest point
构成其最高点的冰川
has been shrinking roughly at the rate of half a meter a year
每年大约以半米的速度缩小
for the last 50 years.
我们在凯布讷山这里看到的
What we’re seeing here at Kebnekaise
本身不会破坏这个星球的稳定
on its own will not destabilize the planet.
但是在北极和南极的
But having two caps of a permanent ice
两个永久性冰盖
in the Arctic and in Antarctica is
是这个星球维持这种状态的先决条件
the very precondition for the planet to stay in this state
使我们能够发展我们所知的文明
that has enabled us to develop civilizations as we know it.
这就是为什么看到冰川消融
And that’s why it’s such an enormous concern
令人非常担忧的原因
to see glaciers melting,
不管是凯布讷山的小冰川
irrespective of whether it’s a small glacier at Kebnekaise,
还是我们正在谈论的格陵兰岛
or whether we’re talking about Greenland,
因为它们加在一起
because they all add together
有着让这个星球降温的神奇能力
to this fantastic capacity of cooling the planet.
这种冷却效应在整个全新世
This cooling effect was fundamental
是维持地球温度的根本
in keeping the Earth’s temperature stable throughout the Holocene.
这个星球的冰层刚好把足够的太阳能量
The planet’s ice was reflecting just the right amount of the Sun’s energy
反射回太空
back into space.
像我们在这里看到的永久性白色表面
A permanent white surface like what we can see around us here
将90、95%来自太阳的能量反射回去
is reflecting back 90, 95% of incoming heat from the Sun.
当这些冰盖开始消融时
When these ice sheets start melting,
它们不仅尺寸缩小
not only do they shrink in size
边缘区域也很暗会吸收热量
so the fringe areas are very dark and absorb heat,
但是即使只是在冰面上得到液体表面的事实
but even just the fact that you get liquid surface on the ice
也会使颜色发生如此显著的变化这样就会达到这种情况
changes the color so significantly, so you can come to a point
冰盖会翻转 从自冷
where the ice sheets tip over from being self-cooling
变成自暖
to becoming self-warming,
这是地球系统里最具戏剧性的
and that is the most dramatic tipping point
临界点
in the Earth’s system.
临界点是指
A tipping point is a point
改变无法逆转的点
beyond which a change becomes irreversible.
它就像是停在坡道上的火车
It’s like a train that’s parked on a slope,
开始移♥动♥
and it’s beginning to move.
火车的刹车失灵了
We’re losing the brakes on the train,
火车在加速
and so the train is accelerating,
开得越来越快在某一刻 我们失去了控制
getting faster and faster, and at some point, we lose control.
我们已经失去了
We are already losing the brakes
可以阻止格陵兰岛冰盖消融的刹车系统
that could prevent the melting of the Greenland ice cap.
我20岁第一次来这里时
When I first came here, aged 20,
感觉就像是场梦…
it felt like kind of a dream,
丹麦和格陵兰岛地质调查局
杰森博克斯教授
…因为我看到了只能在教科书上看到的风景
because I was seeing landscapes that I had only kind of seen in textbooks.
因为其证据和见解杰森是全世界众多
Jason is one of the many scientists around the world
为约翰研究提供基础的科学家中的一员
whose evidence and insights were fundamental to Johan’s research.
格陵兰岛上的千年积雪
The millennia snowfall onto Greenland has accumulated,
产生了这个冰穹
produced this dome of ice.
冰穹有3,2公里里厚而且就在大气层里
It’s two miles thick and, you know, well up in the atmosphere.
那里真的很冷
It’s really cold up there.
冰穹在消融时 冰盖表面
As it melts, the surface of the ice cap
降低到更温暖的空气中
lowers into warmer air,
加快了消融速度
speeding up the melt.
冰穹消融得越多
The more it melts,
气候就需要变得越冷 才能使冰穹逆转
the cooler the climate would need to become in order to reverse it.
但如今的气候对格陵兰岛来说已经太热了
But today’s climate is already too hot for Greenland.
所以在目前的气候下格陵兰岛已经超出了它的临界值
So in the current climate, Greenland is already beyond its threshold,
它现在每秒有1万立方米的冰块消失
er, where it’s now losing 10,000 cubic meters of ice per second.
这是平均损失率
That’s the average loss rate.
现在 损失率只会随着
Now, that loss rate will only continue
气候变暖持续下去
as the climate heats up.
格陵兰岛无法恢复了吗？
So is Greenland lost?
显然是的
Evidently, it is.
除非我们能显著冷却地球的气候
Unless we can significantly cool the Earth’s climate,
否则格陵兰岛冰盖的消融将会不可避免地继续下去
the melting of the Greenland ice cap will inevitably continue.
这里的戏剧性在于临界点的一个特点是
The drama here is that one characteristic of tipping points
一旦你按下了开始按钮就无法加以阻止
is that once you’ve pressed the on button, you cannot stop it.
它占了上风 一切太迟了你又不能说：
It takes over. It’s too late. It’s not like you could say,
“糟糕 现在我才意识到我不想让格陵兰岛的冰层消融
“Oops. Now I realize I didn’t want to melt the Greenland ice sheet.
我们退回去吧”
Let’s… Let’s back off.”
那就太迟了
Then, it’s too late.
但你越过这些临界点时就进入到不可逆转的点
When you cross these tipping points, you can enter a point of no return
像我们这种情况 你基本上可以确定这个星球
that you basically commit the planet to an irreversible sliding away
从支持我们人类的状态 滑向不可逆转的未来
from a state that, in our case, can support us humans.
格陵兰岛冰盖的消融
The melting of Greenland’s ice cap
将使全世界的海平面上升七米
would raise sea levels around the world by seven meters.
想象一下海平面变化的世界
Imagine a world where sea level is not static.
随着它的改变Where it’s changing.
数以百计的沿海城市 现在正受到海平面上升的威胁
Cities, hundreds of coastal cities now are threatened by rising seas.
海平面的稳定
Er, that stability in sea level was key
是文明发展的关键
to the development of civilization.
我们面临的是《疯狂麦克斯》那样的未来
It’s… It’s a… It’s a Mad Max future that we’re facing.
但是格陵兰岛只是地球极地冰盖中的一个
But Greenland is just one of Earth’s polar ice caps,
但跟它南边的冰盖相比要小得多
and it’s dwarfed by its southern twin.
就在几年前
Not so many years ago,
人们还在认为 南极洲是能够迅速恢复的系统
it was thought that Antarctica was the resilient system.
因为冰层受气候的影响不算大
This was the ice sheet that was not very much affected by climate change.
但是如今 这种情况已经完全改变了
But today, that has changed completely.
如今 我们看到南极洲消融的块体和冰块
Today we’re seeing accelerated loss of mass
加快了进入海洋的速度
and loss of ice into the ocean in Antarctica.
如果南极洲西部完全消融
West Antarctica would lead to sea-level rise of more than five meters
将导致海平面上升超过5米
if it were to melt down completely,
而南极洲东部是西部的十倍
and then east Antarctica actually holds the tenfold of that,
所以海平面有上升超过50米的可能性
so more than 50 meters worth of sea-level potential.
里卡达是约翰的一位同事
Ricarda is one of Johan’s colleagues,
她研究的是临界点如何相互影响
and she studies how tipping points can interact.
这里要说明的重要一点是
The important point to make here is that everything
地球系统中的所有事物都是相互关联的
in the Earth’s system is connected.
如果气候系统的一部分
If one part of the climate system
越过了临界点
crosses its tipping point,
那么系统中的其他部分
then that might make it more likely
也很有可能越过其关键临界值
for other parts of the system to also cross their critical threshold,
你可以用多米诺骨牌来思考这个问题
so you can think of this in terms of dominoes.
如果你翻倒其中一个
If you tip one of them over,
那就可能会导致串联反应
then this might lead to a cascading effect.
显然 随着全球气候持续变暖
What is clear is that with ongoing global warming,
我们正在增加
we’re increasing the risk
越过地球系统临界点的风险
of crossing tipping points in the Earth’s system.
当我们越过临界点时我们就启动了不可逆转的变化
When we cross tipping points, we unleash irreversible changes
这就意味着这个星球将从我们最好的朋友
that would mean that the planet will go from our best friend
变成抑制并降低压力的状态