What's the Difference Between 1.5℃ and 2℃ofGlobal Warming? 全球升温1.5℃和2℃有什么不同？

联合国气候报告反复强调，要把全球升温幅度控制在1.5℃以内。此前《巴黎协定》提出的目标是，要把升温幅度控制在2℃以内，同时尽力不超过1.5℃。那么，全球升温1.5℃和 2℃的区别到底有多大？

Over and over at the UN climate summit in Glasgow， world leaders have stressed the need to limit global warming to 1.5℃.

The 2015 Paris Agreement commits countries to limit the global average temperature rise to well below 2℃ above pre-industrial levels， and to aim for 1.5℃.

Scientists  have said crossing the 1.5℃ threshold risks unleeshin6 far more severe climate change effects on people， wildlife and ecosystems.

But what is the difference between 1.5℃ and 2℃ of global warming？

Already， the world has heated to around 1.1℃ above pre-industrial levels. Each of the last four decades was hotter than any decade since 1850.

“We never had such a global warming in only a few decades，” said climate scientist Daniela Jacob at the Climate Service Center Germany.“Halfa  degree  means  much  more  extreme weather， and it can be more intense， or extended in duration.”

在英國格拉斯哥举行的联合国气候变化大会上，世界各国领导人反复强调，必须把全球升温幅度控制在1.5℃以内。

2015年达成的《巴黎协定》中，各国政府承诺将全球平均温度控制在比前工业化水平升温2℃以内，并努力达到升温1.5℃以内的目标。

科学家指出，升温幅度超过1.5℃意味着人类、野生动植物和生态系统都可能遭受气候变化带来的更严重后果。

但全球升温1.5℃和2℃有什么不同呢？

当前，全球温度已经比前工业化水平高出约1.1℃。过去四个十年的气温比1850年以来的任何一个十年都更高。

德国气候服务中心的气候科学家丹妮拉·雅各布说：“仅仅数十年就升温这么多，这样的全球变暖是从未发生过的。升温0.5℃意味着更极端的天气会更频繁地出现，而且极端天气会更恶劣或持续更长时间。”

“Climate change is already affecting every inhabited region across the globe，” said climate scientist Rachel Warren at the University of East Anglia in Britain.

More warming to 1.5℃ and beyond will worsen such impacts . For example， heatwaves would become both more frequent and more severe.

A warmer atmosphere can also hold more moisture， resulting in more extreme rainfall that raises flood risks . It also increases evaporation， leading to more intense droughts.

“At 1.5℃， there's a good chance we can prevent most of the Greenland and west Antarctic ice sheet from collapsing，” said climate scientist Michael Mann at Pennsylvania State University in the US.

But blow past 2℃ and the ice sheets could collapse， Mann said， with sea levels rising  up to 10 meters — though  how quickly that could happen is uncertain.

Warming of 1.5℃ would destroy at least 70% of coral reefs， but at 2℃ more than 99% would  be lost . That would destroy fish habitats and communities that rely on reefs for their food and livelihoods.

英国东英吉利亚大学的气候科学家瑞秋·沃伦说：“气候变化已经影响到了人类居住的每个角落。”

全球升温超过1.5℃将会加剧气候变化的影响。比如，高温将会更频繁地来袭，程度也会更严重。

气温升高还会让大气聚集更多水汽，引发更多强降雨，从而增加洪水风险。气温升高还会使得蒸发量增加，从而导致更严重的干旱。

美国宾夕法尼亚州立大学的气候科学家迈克尔·曼恩说：“如果升温幅度在1.5℃以内，我们还有可能防止格陵兰岛和南极西部的大部分冰盖融化崩塌。”

曼恩说，但是如果升温幅度超过2℃，冰盖就会瓦解，海平面会上升10米之多。不过，不确定这一天来得会有多快。

全球升温1.5℃会摧毁至少70%的珊瑚礁，升温2℃则会使得超过99%的珊瑚礁死亡。这对于依赖珊瑚觅食和栖息的鱼群来说是一个毁灭性打击。

Warming of 2℃， versus 1.5℃， would also increase the impact on food production.

“If you have crop failures in a couple of the breadbaskets of the world at the same time， then you could see extreme food price spikes and hunger and famine across wide swathes of the world，” said climate scientist Simon Lewis at University CollegeLondon.

A warmer world could see the mosquitoes that carry diseases such as malaria and dengue fever expand across a wider range. But 2℃ would also see a bigger share of insects and animals lose most of their habitat range， compared with 1.5℃， and increase the risk of forest fires—another risk to wildlife.

As the world heats up， the risk increases that the planet will reach “tipping points” ， where Earth's systems cross a threshold that triggers irreversible or cascading impacts. Exactly when those points would be reached is uncertain.

全球升溫由1.5℃到2℃，还会加大对粮食生产的影响。

伦敦大学学院的气候科学家西蒙·路易斯说：“如果世界上的几个粮食主产地同时发生农作物歉收，大范围的食品价格飞涨和饥荒将会席卷全球。”

全球变暖会导致携带疟疾和登革热病毒的蚊虫大范围滋生。相比升温1.5℃，升温2℃会让更多昆虫和动物失去大部分栖息地，还会增加森林火灾风险，进而危及野生动植物的生存。

随着全球变暖，地球达到“临界点”的风险也会增加。一旦到达这个临界点，就会触发地球系统不可逆转的连锁效应。但具体何时到达临界点还不确定。”

Word Study

unleash /ʌn'liːʃ/ v.突然释放；使爆发

collapse /kə'læps/ v.崩塌；崩溃

The roof collapsed under the weight of snow.

price spike 价格飙升；价格激增