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下一次冰河世纪何时来临?

When will the next ice age happen? - Lorraine Lisiecki

两万年前
Twenty thousand years ago,
地球是个被严寒笼罩的大陆 猛犸象在此游荡
the Earth was a frigid landscape where woolly mammoths roamed.
巨大的冰块 有几千米厚
Huge ice sheets,several thousand meters thick,
冰封了北美的部分 亚洲和欧洲
encased parts of North America,Asia, and Europe.
我们通常称之为“冰河时代”
We commonly know it as the”Ice Age.”
但是地理学家称之为末次盛冰期
But geologists call itthe Last Glacial Maximum.
那是因为它是最近的
That ’ s because it ’ s the most recent time
形成这么大的冰块覆盖范围的时代
that ice reached such a huge extent,
并且“冰河时代”是个非正式的定义 没经过一致的定义
and “ ice age ” is an informal term without a single agreed-upon definition.
在过去的百万年里
Over the last million years,
实际上经历了10次不同的盛冰期
there have actually been about 10 different glacial maxima.
纵观地球历史 气候经历了极大地变化
Throughout Earth’s history,climate has varied greatly.
数百万年以来 这个星球都没有极地冰盖
For hundreds of millions of years, the planet had no polar ice caps.
没有这些冰 海平面会比现在高70米
Without this ice,the sea level was 70 meters higher.
在另一种极端情况 大约七亿年前
At the other extreme,about 700 million years ago,
地球几乎完全被冰所覆盖
Earth became almostentirely covered in ice
在众所周知的“雪球地球”时期
during an event knownas “Snowball Earth.”
是什么导致了地球气候发生如此大的波动?
So what causes these massive swingsin the planet’s climate?
最主要的诱因是大气中的二氧化碳
One of the main driversis atmospheric carbon dioxide,
一种吸热的温室气体
a greenhouse gas that traps heat.
自然作用 像火山作用
Natural processes, such as volcanism,
岩石的化学风化 有机物的掩埋
chemical weathering of rocks, and the burial of organic matter,
经过数百万年的持续作用都能导致二氧化碳含量的巨大变化
can cause huge changes in carbon dioxide when they continue for millions of years.
过去的百万年间 二氧化碳含量相对较低
Over the past million years,carbon dioxide has been relatively low,
并且盛冰期的反复是由
and repeated glacial maxima have been caused by cycles
地球围着太阳转的周期所引起
in Earth ’ s movement around the sun.
随着地球的转动
As Earth rotates,
地轴发生变化 其倾斜度改变了
it wobbles on its axis and its tilt changes,
照在地球表面不同区域的日照量发生了变化
altering the amount of sunlight that strikes different parts of its surface.
这种偏离 再结合地球的椭圆轨道
These wobbles, combinedwith the planet’s elliptical orbit,
引起了夏季温度的变化
cause summer temperatures to vary depending
其取决于夏至的到来 是在靠近太阳的时候
on whether the summer solstice happens when Earth is closer
或者是在远离太阳的时候
or farther from the sun.
大约每十万年
Approximately every 100,000 years,
这些因素相结合会产生显著的 比上个千年更冷的气候条件
these factors align to create dramatically colder conditions that last for millennia.
凉爽的夏天不够热
Cool summers that aren ’ t warm enough
无法融化之前冬季的雪
to melt the preceding winter ’ s snow
从而导致雪一年一年的不断积累
allow ice to accumulate year after year.
这些冰层将更多的太阳能反射到空中
These ice sheets produceadditional cooling
来实现近一步的降温
by reflecting more solar energyback into space. Simultaneously,
与此同时 更冷的气候条件
cooler conditionstransfer carbon dioxide
将二氧化碳从大气中转移到海洋里
from the atmosphere into the ocean,
引起更严重的降温和冰封扩散
causing even more coolingand glacier expansion.
大概两万年前
About 20,000 years ago,
当地球轨道发生变化后 这一趋势发生了转变
these trends reversed when changesin Earth’s orbit increased summer sunshine
随着夏日不断变强的日光照射在巨大的冰川上 冰川开始融化
over the giant ice sheets,and they began to melt.
海平面上升了130米
The sea level rose 130 meters
二氧化碳从海底重新释放到大气当中
and carbon dioxide was released from the ocean back into the atmosphere.
通过分析花粉和海洋化石
By analyzing pollen and marine fossils,
地理学家能够断定气温在6000年前达到顶峰
geologists can tell that temperaturespeaked about 6,000 years ago,
至少在下次地球轨道转换引起新一轮降温前
before another shift in Earth’s orbitcaused renewed cooling.
那么下次会发生什么呢
So what’s coming next?
根据已有气候数据所体现的自然周期
Based on the repeated natural cycle seenin the climate record,
我们一般认为
we ’ d normally expect the
地球在接下来的数千年
Earth to continue a trend of gradual cooling
将一直保持逐渐降温的趋势 然而
for the next few thousand years. However,
这种降温在150年前突然发生了转变
this cooling abruptlyreversed about 150 years ago.
这是为什么呢?
Why?
大气中的二氧化碳水平
Carbon dioxide levels
从19世纪开始一直上升
in the atmosphere have been rising since the 19th century,
主要是由于化石燃料的使用
when fossil fuel use increased.
这是根据对南极洲的冰中气泡的研究得知的
We know that from studying air bubblestrapped in Antarctic ice.
二氧化碳的大量释放同样和
This surge in carbon dioxidealso coincides
全球气温上升了将近一摄氏度相符
with a global temperature increaseof nearly one degree Celsius.
冰核以及大气监测站
Ice coresand atmospheric monitoring stations
告诉我们 二氧化碳的含量增长速度在不断加快
show us that carbon dioxide levelsare rising faster,
并达到了比过去80万年都要高的程度
and to higher levels, than at any point in the last 800,000 years.
计算机模型预测下一个一到四摄氏度的增长
Computer models forecast another one to
将发生在2100年前
four degrees Celsius of warming by 2100,
这取决于我们使用多少额外的化石燃料
depending on how muchadditional fossil fuel we burn.
这对于当前格陵兰岛和南极的冰层意味着什么?
What does that mean for the ice currently on Greenland and Antarctica?
过去的气候变化表明 即便温度微微上升
Past climate changes suggest that evena small warming shift
都会导致冰融化的过程持续上千年
can begin a process of ice melt that continues for thousands of years.
在本世纪末
By the end of this century,
冰川的融化预计将
ice melt is expected to raise
导致海平面上升30到100厘米
the sea level by 30 to 100 centimeters,
足以影响许多海滨城市和岛国
enough to impact many coastal citiesand island nations.
如果每一千年增加四摄氏度的趋势一直持续
If a four-degree Celsius warming persistedfor several millennia,
海平面将上升10米之多
the sea level could riseby as much as 10 meters.
通过研究过去的气候
By studying past climates,
科学家更深入的了解了究竟是什么使冰的转变
scientists learn more about what drives the shifts in ice
在百万年间影响着我们的星球
that have shaped our planetfor millions of years.
研究表明 现在就开始采取行动
Research suggests thatby taking action now
快速地减少二氧化碳排放
to reduce carbon dioxideemissions quickly,
我们将有机会控制冰川融化 拯救海滨城市
we still have the opportunity to curb ice loss and save our coastal communities.

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视频概述

分析了气候变暖的原因以及后果,呼吁国际采取行动

听录译者

收集自网络

翻译译者

九霄

审核员

审核员 V

视频来源

https://www.youtube.com/watch?v=I4EZCy14te0

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