哈佛大學實驗既瘋狂又有爭議性的地球降溫計劃

In a lab at Harvard, researchers are trying to replicate the conditions of the stratosphere–the part of the atmosphere that stretches roughly six to 31 miles above the surface of the planet–in test tubes. Their goal: to better understand what might happen if humanity eventually decides to embark on a radical, controversial plan to temporarily cool the planet by spraying clouds of particles into the sky.

在哈佛大學的一個實驗室裏，研究人員試圖在試管中複製平流層的條件--大氣層的一部分，在地球表面上延伸約6至31英里。他們的目標是：更好地理解如果人類最終決定開始一項激進的、有爭議的計劃——通過向天空噴出粒子云來暫時冷卻地球——什麼將會發生。

If it ever happens, the process might involve sending planes into the sky to release particles of a compound like sulfur dioxide that can reflect some sunlight back into space and could temporarily cool the planet. It's not a fix for climate change, and it's a form of geoengineering so extreme that it carries risks that may not be fully predictable. But as climate change progresses, it's possible that the global community may someday decide it has to try it.

如果真的發生了這種情況，這個過程可能包括向空中發射飛機，使其釋放二氧化硫等化合物的粒子，這種化合物能將一些陽光反射回太空，並能暫時讓地球降溫。它不是氣候變化的解決措施，而是一種極端的地球工程方案，它帶來的風險可能無法完全預測。但隨着氣候變化的惡化，地球委員會有可能在某一天決定必須嘗試一下這個方案。

"Our team here is doing the research because we believe there's still a lot of uncertainties around solar geoengineering, and we think there's a chance for potential benefits around the world," says Elizabeth Burns, managing director for Harvard's Solar Geoengineering Research Program. "But we also think there's the chance for very real risks."

哈佛大學太陽能地球工程研究項目總經理伊麗莎白·伯恩斯說:"我們的團隊正在進行這項研究，因爲我們相信太陽能工程仍然存在很多不確定性，我們認爲全世界都有可能從中受益。"。 "但我們也認爲這存在現實的風險。"

In one new study in Nature Climate Change, researchers from Harvard, MIT, and Princeton used a state-of-the-art, detailed computer model to look at what might happen if solar geoengineering was used to cut global temperature increases in half. In the scenario, they found that reducing warming would also offset the increasing intensity of hurricanes and would help moderate extreme rain and a lack of water for farming (in the model, rain decreased, but so did evaporation). Less than 0.5% of the world might see increases in impacts from climate change. That's in contrast to some previous studies that found that this type of geoengineering might benefit some parts of the world while large other areas were harmed. Still, the study is limited, and doesn't look at all of the potential effects.

在《自然氣候變化》雜誌的一項新研究中，來自哈佛大學、麻省理工學院和普林斯頓大學的研究人員使用了一種最先進的、詳細的計算機模型，來觀察如果利用太陽能工程將全球氣溫上升減半會發生什麼。 在這種情況下，他們發現，減緩氣候變暖也會緩解颶風強度，並有助於緩和極端降雨和農業用水的缺乏(在模型中，降雨減少了，但蒸發也減少了)。 世界上受氣候變化影響的地方不到0.5%。這與之前的一些研究相反，那些研究發現，這種類型的工程可能使世界上的一些地區受益，而其他大部分地區則受到損害。 儘管如此，這項研究是有限的，並沒有看到所有的潛在影響。

The concept of spraying chemicals into the sky to cool the Earth is not new. It's the same process that happens naturally when volcanoes erupt. In 1991, when Mount Pinatubo erupted and spewed millions of tons of sulfur dioxide into the atmosphere, it cooled the planet by half a degree Celsius for more than a year. But it's only more recently that researchers have started seriously studying what might happen if humans deliberately do something similar. At this point, it's still a very small area of study, with relatively little funding, and many unknowns.

向天空噴灑化學物質以冷卻地球的想法並不新鮮。這和火山爆發時自然發生的過程是一樣的。1991年，皮納圖博火山爆發，向大氣中噴射了數百萬噸二氧化硫，使地球降溫0.5攝氏度，持續了一年多。但直到最近，研究人員纔開始認真研究如果人類故意做類似的事情會發生什麼。在這一點上，這仍然是一個非常小的研究領域，資金相對較少並且存在許多未知數。

Burns emphasizes, repeatedly, that the world's priority needs to be reducing emissions to zero. "Solar geoengineering cannot be a substitute for reducing emissions, because it does not address the root cause of climate change," she says. "So if we are to achieve a stable climate, we really do need to reduce emissions to zero, and then also eventually remove the carbon dioxide that's in the atmosphere and store it underground or elsewhere. Those actions actually address the root cause. Solar geoengineering does not."

伯恩斯一再強調，世界的首要任務是實現零排放。 "太陽能工程不能替代減排，因爲它不能解決氣候變化的根本原因,"她說。 "因此，如果我們要實現一個穩定的氣候，我們確實需要將排放量減少到零，然後最終消除大氣中的二氧化碳，並將其儲存在地下或其他地方。這些行動實際上解決了問題的根本。太陽能地球工程則不然。"

"It would only potentially be used temporarily while we rapidly reduce our emissions to the atmosphere and figure out cheap ways to separate carbon dioxide out," says Alan Robock, an environmental sciences professor at Princeton. "So nobody talks about doing it instead of mitigation. It would be on top of our best efforts at mitigation." Robock has documented 27 potential risks of the idea, from the possibility of ozone depletion to potential droughts and a reduction in solar energy generation. The paper lists only six potential benefits, but one is significant: a reduction in surface air temperatures could "reduce or reverse negative impacts of global warming, including floods, droughts, stronger storms, sea ice melting, and sea level rise."

普林斯頓大學環境科學教授艾倫·羅博克(Alan Robock)表示:“在我們迅速減少對大氣的排放，並找到廉價的方法將二氧化碳分離出去的時候，它只可能被暫時使用。”“因此，沒有人談論減排而不是減排。這將是我們在減緩氣候變化方面最大的努力。羅伯克記錄了這個想法的27個潛在風險，從臭氧損耗的可能性到潛在的乾旱和太陽能發電的減少。這篇論文只列出了六個潛在的好處，但其中一個很重要：地表空氣溫度的降低可以"減少或扭轉全球變暖的負面影響，包括洪水、乾旱、強風暴、海冰融化和海平面上升。"

At Harvard, the researchers are studying the possibility of using calcium carbonate (the same particle found in chalk or toothpaste) rather than sulfur dioxide; while sulfur dioxide can speed up the destruction of the ozone layer, calcium carbonate could potentially help it and avoid some other risks. While their work is focused in the lab and computer modeling now, the team may be the first to do a real-world experiment, which would involve launching a balloon into the stratosphere, releasing a small amount of calcium carbonate, and then measure how the light scatters and changes in atmospheric chemistry. The team was interested in conducting the experiment this year, but won't move forward without the recommendation of an external, independent advisory committee that it's creating. "To us, the governance of this is equally as important as the scientific goals for the experiment," says Burns.

哈佛大學的研究者們正在研究使用碳酸鈣的可能性（就是粉筆和牙膏的顆粒成分）而不是二氧化硫，因爲SO2會加速破壞臭氧層。而碳酸鈣能夠防止這種情況同時避免一些其他的風險。而他們的工作是集中在實驗室和計算機建模,團隊可能首先做一個真實的實驗,這將涉及向平流層發射一個氣球,釋放出少量的碳酸鈣,然後測量光散射和大氣化學的變化。該團隊對今年進行這項實驗很感興趣，但如果沒有它正在創建的一個外部獨立諮詢委員會的建議，他們不會推進這項實驗。伯恩斯說:“對我們來說，對這一問題的管理與實驗的科學目標同樣重要。”