Daybreak and Mount Pinatubo bursts angrily into life again.

皮納土波火山的火光在黎明猛然地點亮大地。

It happened on June 15th, 1991 in the north-west of the Philippines.

事件發生在 1991 年 6 月 15 日，菲律賓的西北方。

It was so powerful it produced a gas cloud that reached the stratosphere.

爆炸的威力之大，它所噴發出的氣塵雲到達了平流層的高度。

The explosion caused a lot of damage locally, but the cloud itself did something extraordinary.

火山爆發對當地帶來許多損害，但是它所噴發的雲卻造成了更令人意想不到的事情。

It lowered the Earth's temperature for four years.

它降低了地球的溫度四年。

Sulphur dioxide in the cloud created particles which spread around the Earth.

雲裡的二氧化硫製造出散落到地球各處的粒子。

These then reflected some of the sun's rays into space.

而這些粒子將部分紫外線反射到外太空。

Scientists are looking to mimic the effects of this phenomenon to counter global warming.

科學家在試圖模仿這個現象所產生的效果來對抗地球暖化。

It's a highly controversial concept known as solar geoengineering.

這是一個具有高度爭議性的概念，叫作太陽能地球工程。

Climate change is probably the biggest problem humanity faces today.

氣候變遷大概是人類目前所面臨最大的問題。

In the past 25 years the global average temperature has risen by around 0.5°C.

在過去 25 年全球的平均溫度已經上升了約攝氏 0.5 度。

The accumulation of carbon in the atmosphere is warming the Earth up, making more intense hurricanes, rains, higher temperatures.

大氣中累積的二氧化碳正在使地球升溫，造成更加強烈的颶風、降雨和高溫。

So far governments have focused on policies for cutting emissions but they keep rising.

目前為止各國政府聚焦在制定減少排放量的政策，但排放量仍持續上升。

The concentration of carbon dioxide in the atmosphere has risen 15% since 1994.

從 1994 年起，大氣中二氧化碳的濃度已經上升了百分之 15 。

The Paris Agreement, signed by 175 parties in 2016, was a sign that countries were willing to work together to cut emissions.

《巴黎協議》在 2016 年由 175 個國家及團體共同簽署，這象徵著各國願意攜手合作，共同減低溫室氣體的排放量。

But not every world leader is on board.

然而，並非所有國家領袖都站在同一個陣線。

The Paris Climate Accord is simply the latest example of Washington entering into an agreement that disadvantages the United States.

《巴黎氣候協議》只是華盛頓加入不利於美國的協議的一個最新例子。

If emissions aren't reduced, what next?

如果排放量沒有減少，接下來會發生什麼事？

Theoretically solar geoengineering could cool the entire planet.

理論上來說，太陽能地球工程是可以降低整個星球的溫度。

It's actually potentially incredibly simple because all you need to do is inject a bunch of particles into the stratosphere and there's a number of ways you could do that.

它事實上應該是非常地簡單，因為我們只需要將一堆粒子注入到大氣層，而我們有很多方法可以達成。

Recently a study out of Yale and Harvard looked at the details of how this would be done.

最近耶魯和哈佛的一項研究構思出如何執行這個計畫的細節。

In that Harvard and Yale study, they imagined building a fleet of planes.

在那項耶魯和哈佛的研究中，他們設想打造一支機隊。

Up to 95 of them.

高達 95 架飛行器。

That would make 60,000 flights a year.

它們能夠在一年執行 6 萬次飛行。

The fleet would spread hundreds of thousands of tonnes of sulphur dioxide into the stratosphere every year.

機隊每年會將幾十萬公噸的二氧化硫散佈至平流層。

After 15 years they reckon the world would cool by 0.3°C.

他們預估 15 年後全世界可以降低攝氏 0.3 度。

But there are reasons not to do this.

但是有一些不能這麼做的原因。

One of the biggest concerns is that it could make governments complacent.

其中最大的一個隱憂就是，各國政府可能會滿足於此。

The big worry is that it will be exploited to argue against emissions cuts.

最擔心的就是這會成為反對減少排放量的藉口。

Geoengineering is a supplement to cutting emissions, not a substitute for cutting emissions.

地球工程是協助降低排放量的一個工具，而不是替代方案。

It would also be politically messy.

它還會造成政治混亂。

If the plan is to put a thermostat on the Earth, deciding who has their hand on the dial won't be easy.

假設這個計畫是在地球上架設一台溫度調節器，決定誰能夠掌控調節器將非常困難。

For it to have a global effect, you're going to need all governments on board, and that is going to be extremely difficult.

要讓它達到一個全球性的效果，我們會需要所有政府的同意，而那將會非常地困難。

If a country went alone and decided to do it on its own then obviously because the impacts are going to be regional or global, you could create a lot of international tension.

如果一個國家決定獨自進行這個計畫，那麼，很明顯地，由於這個影響會是地區性甚至是全球性的，那將會造成許多緊張的國際情勢。

A Swiss proposal to study geoengineering and how it should be regulated was recently put forward at the UN Environment Assembly.

在最近一次的聯合國環境大會 (2019.03) 上，瑞士提出一項關於研究地球工程以及該如何規範它的提案。

But America and Saudi Arabia opposed the motion.

但是美國及沙烏地阿拉伯反對了這項提案。

Possibly because they don't want international regulation of geoengineering.

大概是因為他們不希望地球工程有國際法規。

As things stand, not enough is known about how it could impact the climate or the chemistry of the atmosphere.

就目前的情況來說，這會對氣候或是大氣中的化學反應造成什麼樣的影響，我們所掌握的仍然有限。

There could be unexpected consequences.

有可能會出現我們預想不到的後果。

You can affect rain patterns and you might cause a region that is already suffering from drought to have even less water.

這可能影響降雨模式，可能會使一個原本就受乾旱所苦的地區變得更加缺水。

A lot more basic research both into how we would do it but also what the consequences of it would be if we did it in one way or in another way is needed.

我們仍需要做許多基本的研究，不論是該如何進行，或是如果以不同方法進行會帶來怎麼樣不同的結果。

But of course, if we don't do it, there's deep uncertainty about how much climate change we get for a given amount of CO₂ in the air.

不過，當然，如過我們不這麼做，我們完全無法確定空氣中這麼多的二氧化碳會帶來什麼樣程度的氣候變遷。

Both of those are risky, both are uncertain, the question is which has higher risk?

兩者都有風險，兩者都充滿未知，重點是哪一個的風險更高？

The politics of solar geoengineering are so complex that it might never happen.

太陽能地球工程所牽涉到的政治因素太過複雜，它大概永遠無法實施。

That said, as the world continues to warm the case for exploring radical measures grows stronger.

也就是說，隨著地球繼續升溫，找出根本性的解決方案日益迫切。