美国国家公共电台 NPR--Here are 3 dangerous climate tipping points the world is on track for

Here are 3 dangerous climate tipping points the world is on track for

Transcript¹

The goal of the international climate meeting underway in Egypt is to limit global warming to 1.5 degrees Celsius², compared to temperatures in the late 1800s. Even at that level, communities will experience more dangerous storms, flooding and heat waves.

But if the planet heats up beyond 1.5 degrees, the impacts don't get just slightly worse. Scientists warn that abrupt³ changes could be set off, with devastating⁴ impacts around the world.

Such changes are sometimes called climate tipping points, although they're not as abrupt as that term would suggest. Most will unfold over the course of decades. Some could take centuries. Some may be partially⁵ reversible or avoidable. But they all have enormous and lasting⁶ implications for the humans, plants and animals on Earth. And they are looming⁷.

It's still possible to avoid such widespread calamities⁸, but only if countries move far more aggressively to cut the pollution driving climate change. The Earth has warmed about 1 degree Celsius so far. If countries, including the United States, follow through on current promises to reduce greenhouse gas emissions¹⁰, the latest estimates suggest that Earth's temperature will still top out around 2.8 degrees Celsius of warming.

Here are the three most important and well-studied changes, from collapsing¹¹ ice sheets to thawing¹³ Arctic permafrost, to disappearing coral reefs.

Change #1: Ice sheets in Greenland and West Antarctica could collapse¹⁴

Ice sheets are the massive expanses of ice that cover Greenland and Antarctica, and which contain about two thirds of the freshwater on Earth. Climate change is already causing them to melt, and raising sea levels around the world.

But if the Earth lingers at, or above, 2 degrees Celsius of warming, as it is on track to, that melting will steadily¹⁵ accelerate. Scientists warn that will cause parts of the ice sheets to collapse, sending massive amounts of water into the world's oceans.

The million dollar question is how quickly that collapse will occur. "Collapse tends to be a bit of a loaded world. People think of it like a building collapse," says Ian Joughin, a glaciologist at the University of Washington who has spent decades studying how giant glaciers¹⁷ move and change.

"Maybe a better timescale for an ice sheet [collapsing] is the Roman Empire," Joughin explains. Like a dying empire, the ice sheets in Greenland and West Antarctica are huge. It will take decades or even centuries for them to disintegrate¹⁸.

This year marks the 26th year that Greenland has lost more ice than it gained. Last year, rainfall was recorded at the ice sheet's highest point, rather than snow, a sign that warmer temperatures were triggering widespread melting.

As temperatures continue to warm, scientists say the two-mile thick ice sheet is getting out of balance. Snow and ice are melting faster than they're being replaced, and as the ice melt accelerates, the process is difficult to stop. One study found that no matter how humans cut greenhouse gas emissions going forward, the melting of the Greenland ice sheet is likely to cause 10 inches of sea level rise.

Research suggests that the collapse of the West Antarctic ice sheet may already be underway. A massive glacier¹⁶ there, which covers an area about the size of the state of Washington, is melting quickly in response to climate change, and could splinter into the ocean in the coming decades.

If that glacier melts entirely¹⁹, it will add so much water to the oceans that sea levels will rise about 2 feet. If the entire West Antarctic ice sheet melts, scientists estimate that sea levels will rise about 12 feet.

Due to their enormous size, ice sheets have a huge amount of inertia²⁰. Once the melt process gets underway, it's difficult to stop.

"It takes a few hundred years to really get going," says Joughin. "And it's kind of a snowball effect, where the faster it goes, the more it's going to go."

But it will take a long time for people around the world to feel the most extreme effects of that melt. "It could be anywhere from two or three hundred years to a thousand years," says Joughin.

If humans slow down the pace of global warming, it will help slow down the pace of ice melting, giving the billions of people who live along coastlines more time to adapt.

Change #2: Permanently²¹ frozen ground could thaw¹²

Climate change is causing permafrost – the permanently frozen ground in the Arctic – to thaw. And as the Earth approaches 2 degrees Celsius of warming, that thawing ground will cause both local and global problems.

Let's start local. When permafrost thaws²², the ice that's trapped in the ground turns into water and drains away. "It can have really profound consequences," says Merritt Turetsky, the director of the Institute of Arctic and Alpine²⁴ Research at the University of Colorado, Boulder²⁵. "We can see lakes draining overnight. We can see ecosystems²⁷ becoming much drier in some areas, because the permafrost was actually holding the water up at the surface."

That's because when the ground is frozen, it's impermeable²⁸ to moisture, like the lining²⁹ of a bathtub. "When it thaws, we pull the drain out of the bathtub," Turetsky explains.

Thawing permafrost has profound impacts for the millions of people who live in the Arctic. In many places, the land is sinking as it thaws, cracking the foundations of buildings, buckling³⁰ roads and runways and kinking pipelines³¹. That will accelerate as the Earth heats up more.

Thawing permafrost also has global climate implications. Permanently frozen ground is like the world's freezer: millennia³² of dead plants and animals are locked up in permafrost.

"When permafrost thaws it's a little like losing power to your freezer. That food starts to rot," explains Ted⁹ Schuur, a permafrost expert at Northern Arizona University. Bacteria and fungi³³ start to digest the carbon-rich soil, releasing planet-warming methane³⁴ and carbon dioxide into the atmosphere.

Basically, it's an infinite loop of greenhouse gasses: human emissions cause the planet to heat up. That heat thaws permafrost, which releases more emissions.

But how much extra carbon ultimately gets released by Arctic permafrost in the future is up to humans. "The faster we can decarbonize society today, the more permafrost carbon we can keep in the Arctic ground where it belongs," says Turetsky. For example, by using renewable energy instead of burning fossil fuels.

But, she warns, there will be a lag: the warming that has already occurred will keep thawing permafrost for decades. "Our climate warming today is going to thaw permafrost and cause that permafrost to lose carbon 50 years from now," Turetsky explains.

Change #3: Coral reefs could be gone forever

By overall area, coral reefs are a tiny part of the ocean. But they're a bedrock ecosystem²⁶ for marine³⁵ life, supporting an estimated 25% of all species.

Corals are highly sensitive to heat, and as the oceans warm, the future of reefs is in peril³⁶. When marine heat waves hit, corals under stress expel their algae³⁷ companions, which they need to survive. The reefs turn a ghostly white color.

A bleaching³⁸ event doesn't necessarily mean the end for a coral reef. Corals have the ability to recover, given enough time. But repeated heat waves, as seen at Australia's Great Barrier Reef, can kill a reef, leading to the collapse of the ecosystem.

Oceans are also becoming more acidic, as they absorb the carbon dioxide that humans emit from burning fossil fuels. That also stresses corals, making it difficult for them to build their skeletons.

If the world passes 2 degrees Celsius of heating, an estimated 99% of the world's coral reefs could be lost. The damage is happening faster than scientists expected. Combined with the effects of pollution and human development, half of all reefs worldwide will be in unlivable conditions by 2035, according to a new study.

"The coming decades will bring, I think, unprecedented³⁹ change for both these reef systems and humanity in general," says Erik Franklin, professor at Hawaii Institute of Marine Biology at the University of Hawaii at Manoa, who worked on the study.

It's estimated that half a billion people around the world depend on coral reefs for food, income and livelihoods⁴⁰. Losing reefs would destabilize many countries, along with risking extinction⁴¹ for marine life that can only be found on coral reefs.

"There's entire societies and economies that are built around reef systems, especially in equatorial and tropical regions," Franklin says. "So these societies will be in dire²³ straits."

Many scientists are searching for "refuges" – pockets of the ocean where conditions might remain livable for coral reefs. The hope is that coral reefs can hold on there, surviving just long enough until humans can get their heat-trapping emissions under control.

1 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

2 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

3 abrupt   

adj.突然的，意外的；唐突的，鲁莽的

参考例句：

• The river takes an abrupt bend to the west.这河突然向西转弯。
• His abrupt reply hurt our feelings.他粗鲁的回答伤了我们的感情。

4 devastating   

adj.毁灭性的，令人震惊的，强有力的

参考例句：

• It is the most devastating storm in 20 years.这是20年来破坏性最大的风暴。
• Affairs do have a devastating effect on marriages.婚外情确实会对婚姻造成毁灭性的影响。

5 partially   

adv.部分地，从某些方面讲

参考例句：

• The door was partially concealed by the drapes.门有一部分被门帘遮住了。
• The police managed to restore calm and the curfew was partially lifted.警方设法恢复了平静，宵禁部分解除。

6 lasting   

adj.永久的，永恒的；vbl.持续，维持

参考例句：

• The lasting war debased the value of the dollar.持久的战争使美元贬值。
• We hope for a lasting settlement of all these troubles.我们希望这些纠纷能获得永久的解决。

7 looming   

n.上现蜃景（光通过低层大气发生异常折射形成的一种海市蜃楼）v.隐约出现，阴森地逼近( loom的现在分词 )；隐约出现，阴森地逼近

参考例句：

• The foothills were looming ahead through the haze. 丘陵地带透过薄雾朦胧地出现在眼前。 来自《简明英汉词典》
• Then they looked up. Looming above them was Mount Proteome. 接着他们往上看，在其上隐约看到的是蛋白质组山。 来自英汉非文学 - 生命科学 - 回顾与展望

8 calamities   

n.灾祸，灾难( calamity的名词复数 )；不幸之事

参考例句：

• They will only triumph by persevering in their struggle against natural calamities. 他们只有坚持与自然灾害搏斗，才能取得胜利。 来自《现代汉英综合大词典》
• One moment's false security can bring a century of calamities. 图一时之苟安，贻百年之大患。 来自《现代汉英综合大词典》

9 ted   

vt.翻晒，撒，撒开

参考例句：

• The invaders gut ted the village.侵略者把村中财物洗劫一空。
• She often teds the corn when it's sunny.天好的时候她就翻晒玉米。

10 emissions   

排放物( emission的名词复数 )； 散发物（尤指气体）

参考例句：

• Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
• Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。

11 collapsing   

压扁[平]，毁坏，断裂

参考例句：

• Rescuers used props to stop the roof of the tunnel collapsing. 救援人员用支柱防止隧道顶塌陷。
• The rocks were folded by collapsing into the center of the trough. 岩石由于坍陷进入凹槽的中心而发生褶皱。

12 thaw   

v.（使）融化，（使）变得友善；n.融化，缓和

参考例句：

• The snow is beginning to thaw.雪已开始融化。
• The spring thaw caused heavy flooding.春天解冻引起了洪水泛滥。

13 thawing   

n.熔化，融化v.（气候）解冻( thaw的现在分词 )；（态度、感情等）缓和；（冰、雪及冷冻食物）溶化；软化

参考例句：

• The ice is thawing. 冰在融化。 来自《现代英汉综合大词典》
• It had been snowing and thawing and the streets were sloppy. 天一直在下雪，雪又一直在融化，街上泥泞不堪。 来自英汉文学 - 嘉莉妹妹

14 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

15 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

16 glacier   

n.冰川，冰河

参考例句：

• The glacier calved a large iceberg.冰河崩解而形成一个大冰山。
• The upper surface of glacier is riven by crevasses.冰川的上表面已裂成冰隙。

17 glaciers   

冰河，冰川( glacier的名词复数 )

参考例句：

• Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
• It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川，又有雨林和秀丽的山峰。 来自英语晨读30分（高一）

18 disintegrate   

v.瓦解，解体，（使）碎裂，（使）粉碎

参考例句：

• The older strata gradually disintegrate.较老的岩层渐渐风化。
• The plane would probably disintegrate at that high speed.飞机以那么高速飞行也许会四分五裂。

19 entirely   

ad.全部地，完整地；完全地，彻底地

参考例句：

• The fire was entirely caused by their neglect of duty. 那场火灾完全是由于他们失职而引起的。
• His life was entirely given up to the educational work. 他的一生统统献给了教育工作。

20 inertia   

adj.惰性，惯性，懒惰，迟钝

参考例句：

• We had a feeling of inertia in the afternoon.下午我们感觉很懒。
• Inertia carried the plane onto the ground.飞机靠惯性着陆。

21 permanently   

adv.永恒地，永久地，固定不变地

参考例句：

• The accident left him permanently scarred.那次事故给他留下了永久的伤疤。
• The ship is now permanently moored on the Thames in London.该船现在永久地停泊在伦敦泰晤士河边。

22 thaws   

n.（足以解冻的）暖和天气( thaw的名词复数 )；（敌对国家之间）关系缓和v.（气候）解冻( thaw的第三人称单数 )；（态度、感情等）缓和；（冰、雪及冷冻食物）溶化；软化

参考例句：

• The sun at noon thaws the ice on the road. 中午的阳光很快把路上的冰融化了。 来自辞典例句
• It thaws in March here. 在此地化雪的季节是三月。 来自辞典例句

23 dire   

adj.可怕的，悲惨的，阴惨的，极端的

参考例句：

• There were dire warnings about the dangers of watching too much TV.曾经有人就看电视太多的危害性提出严重警告。
• We were indeed in dire straits.But we pulled through.那时我们的困难真是大极了，但是我们渡过了困难。

24 alpine   

adj.高山的；n.高山植物

参考例句：

• Alpine flowers are abundant there.那里有很多高山地带的花。
• Its main attractions are alpine lakes and waterfalls .它以高山湖泊和瀑布群为主要特色。

25 boulder   

n.巨砾；卵石，圆石

参考例句：

• We all heaved together and removed the boulder.大家一齐用劲，把大石头搬开了。
• He stepped clear of the boulder.他从大石头后面走了出来。

26 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

27 ecosystems   

n.生态系统( ecosystem的名词复数 )

参考例句：

• There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
• Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样，从雨林到半荒漠等不一而足。 来自辞典例句

28 impermeable   

adj.不能透过的，不渗透的

参考例句：

• The canoe is made from an impermeable wood.独木舟由防水木头制成。
• The external layer of the skin is relatively impermeable to water.皮肤的外层不透水。

29 lining   

n.衬里，衬料

参考例句：

• The lining of my coat is torn.我的外套衬里破了。
• Moss makes an attractive lining to wire baskets.用苔藓垫在铁丝篮里很漂亮。

30 buckling   

扣住

参考例句：

• A door slammed in the house and a man came out buckling his belt. 房子里的一扇门砰地关上，一个男子边扣腰带边走了出来。
• The periodic buckling leaves the fibre in a waved conformation. 周期性的弯折在纤维中造成波形构成。

31 pipelines   

管道( pipeline的名词复数 )； 输油管道； 在考虑（或规划、准备） 中； 在酿中

参考例句：

• The oil is carried to the oil refinery by pipelines. 石油通过输油管输送到炼油厂。
• The oil carried in pipelines. 石油用管道输送。

32 millennia   

n.一千年，千禧年

参考例句：

• For two millennia, exogamy was a major transgression for Jews. 两千年来，异族通婚一直是犹太人的一大禁忌。
• In the course of millennia, the dinosaurs died out. 在几千年的时间里，恐龙逐渐死绝了。

33 fungi   

n.真菌，霉菌

参考例句：

• Students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
• The lawn was covered with fungi.草地上到处都是蘑菇。

34 methane   

n.甲烷，沼气

参考例句：

• The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
• Methane may have extraterrestrial significance.甲烷具有星际意义。

35 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

36 peril   

n.(严重的)危险；危险的事物

参考例句：

• The refugees were in peril of death from hunger.难民有饿死的危险。
• The embankment is in great peril.河堤岌岌可危。

37 algae   

n.水藻，海藻

参考例句：

• Most algae live in water.多数藻类生长在水中。
• Algae grow and spread quickly in the lake.湖中水藻滋蔓。

38 bleaching   

漂白法，漂白

参考例句：

• Moderately weathered rock showed more intense bleaching and fissuring in the feldspars. 中等风化岩石则是指长石有更为强烈的变白现象和裂纹现象。
• Bleaching effects are very strong and show on air photos. 退色效应非常强烈，并且反映在航空象片上。

39 unprecedented   

adj.无前例的，新奇的

参考例句：

• The air crash caused an unprecedented number of deaths.这次空难的死亡人数是空前的。
• A flood of this sort is really unprecedented.这样大的洪水真是十年九不遇。

40 livelihoods   

生计，谋生之道( livelihood的名词复数 )

参考例句：

• First came the earliest individualistic pioneers who depended on hunting and fishing for their livelihoods. 走在最前面的是早期的个人主义先驱者，他们靠狩猎捕鱼为生。 来自英汉非文学 - 政府文件
• With little influence over policies, their traditional livelihoods are threatened. 因为马赛族人对政策的影响力太小，他们的传统生计受到了威胁。

41 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。