《探索》雜誌6月刊：該給地球降降溫嗎？

Amid climate inaction, scientists confront an idea that scares them.

如果氣候不作為，科學家們面臨著一個讓他們感到害怕的想法。

原文：NATHANIEL SCHARPING，Discover 2018年6月刊

翻譯：鳳梨是只胖柯基

校閱：PC

Mount Pinatubo erupted in the Philippines in 1991, spewing millions of tons of ash and chemicals into the atmosphere. Over the next year, large parts of Earth cooled by almost a full degree Fahrenheit.

1991年，皮納圖博火山在菲律賓爆發，向大氣中噴出數百萬噸的火山灰和化學物質。在接下來的一年裡，地球上大部分地區的溫度幾乎都降了1華氏度。

Volcanoes historically have caused some of the planet』s sharpest temperature drops. In addition to ash and fire, they belch sulfur dioxide that lingers as a fine particle spray called an aerosol. These aerosols help Earth』s atmosphere reflect incoming light, creating a cooling effect.

從歷史上看，火山爆發會導致了地球上一些溫度高的地區氣溫下降。除了火山灰和火，它們還會噴出二氧化硫，這是一種叫做氣溶膠的微粒噴霧。這些氣溶膠有助於地球大氣反射入射光，從而產生冷卻效應。

Some scientists speculate that seeding such sulfur aerosols — absent fiery eruptions — could someday be a Hail Mary to counteract climate change. The idea is called geoengineering. Picture fleets of aircraft ferrying sulfur across the stratosphere year-round.

一些科學家推測，在沒有火山爆發的情況下，噴洒這種硫氣溶膠，可能有一天會成為「萬福瑪利亞」，以應對氣候變化。這個想法被稱為地球工程。想像一下每年都有各式飛機在平流層中運送硫。

University of Exeter climatologist Anthony Jones says developing aerosol releasing technology might take a few years — and likely won』t happen for decades — but it is possible.

英國埃克塞特大學的氣候學家安東尼·瓊斯說，研製氣溶膠釋放技術可能需要幾年的時間，而且可能幾十年內都不會發生，但這是可能發生的。

Cost estimates range from around $1 billion to $10 billion per year. That』s less than current spending on climate research and mitigation, and far cheaper than coping with its consequences. Sulfur is even easy to get. It』s a by product of fossil fuel production so abundant that a mining outfit in Alberta, Canada, is stacking the stuff into a sulfur pyramid that could eventually dwarf Egypt』s.

氣溶膠釋放成本預估從每年10億美元到100億美元不等。這比目前在氣候研究和減排方面的支出要少，而且比應對其後果要便宜得多。硫很容易得到，這是化石燃料生產的副產品。在加拿大阿爾伯塔省的一家礦業公司，正把這些東西堆疊在一個硫磺金字塔里，甚至使得埃及的金字塔相形見絀。

The problem? We don』t fully understand the consequences of geoengineering. Few real-world tests have taken place. And that』s driving a surge of new research.

這樣做有沒有什麼問題?我們並不完全了解地球工程的後果。現實中的測試很少發生。但是這推動了一項新的研究。

Later this year, a Harvard University team hopes to gather some of the first real-world data in the Stratospheric Controlled Perturbation Experiment (SCoPEx). The researchers will send a balloon into the stratosphere above Tucson, Arizona, to spray particles across an area roughly half a mile long and a football field wide. A sensor studded gondola will dip back through the cloud to measure how aerosol particles interact with one another and the atmosphere.

今年晚些時候，哈佛大學的一個研究小組希望能在平流層控制的微擾實驗(SCoPEx)中收集到一些真實的數據。研究人員將把一個氣球送到亞利桑那州圖森市上空的平流層，在大約半英里長和一個足球場寬的地方噴洒微粒。一個布滿感測器的狹長小船將會穿過雲層，測量氣溶膠粒子如何相互作用，以及大氣狀況。

「If [geoengineering is] really going to be used in this sort of emergency climate catastrophe scenario, then you』re not going to have that chance to learn about things going into it,」 says climate scientist Ken Caldeira of the Carnegie Institution for Science. 「You pretty damn well better do the research up front.」

卡內基科學研究所的氣候科學家肯·卡爾代拉說:「如果(地球工程)真的要在這種緊急氣候災難場景中使用，那麼了解它的機會就不多了，所以你最好提前做好研究。」

So far, computer climate models simulating solar geoengineering have predicted significant reductions in global warming, Caldeira says.

卡爾代拉說，目前為止，模擬太陽能地球工程的計算機氣候模型已經預測到全球變暖將顯著減少。

Yet researchers are hardly optimistic. 「If you ask me today to vote whether we should geoengineer, or never, ever do it, I would be on the never, ever side,」 says Gernot Wagner, executive director of Harvard』s Solar Geoengineering Research Program.

然而，研究人員們並不樂觀。哈佛大學太陽地球工程研究項目執行主任傑恩·瓦格納說:「如果你今天讓我投票決定我們是否應該做地球工程，做或者永遠不做，我將永遠站在不做那邊。」

Many climate scientists agree. One reason is that aerosols aren』t the opposite of carbon dioxide, says Peter Irvine, a Harvard expert in climate models. Aerosols counteract some symptoms of excess greenhouse gases, but not others, like ocean acidification. And sulfur depletes Earth』s ozone layer. It』s also a long-term commitment: Stop pumping out aerosols, and the climate would snap back. In fact, a January study in Nature Ecology and Evolution showed sporadic geoengineering could be more dangerous for animals adapting to climate change than never attempting it at all.

許多氣候科學家也覺得不該開展地球工程。哈佛大學氣候模型方面專家彼得·歐文說，其中一個原因是氣溶膠並不完全是二氧化碳的對立面。氣溶膠抵消了一些過量的溫室氣體的癥狀，但沒有其他的作用，比如海洋酸化。而硫會耗盡地球的臭氧層。這也是一個長期的保證:停止排放氣溶膠，氣候將會恢復。事實上，1月的《自然生態與進化》研究顯示，對於適應氣候變化的動物來說，偶爾的地球工程可能比從未嘗試過更加危險。

Aerosols also reflect sunlight — instead of trapping heat like CO2 — so they』d overcool the tropics and undercool the poles, creating unpredictable results.

氣溶膠也反射太陽光，而不是像二氧化碳那樣吸收熱量，所以他們會給熱帶地區降溫，給兩極降溫，造成無法預測的結果。

All this makes researchers worry about a rogue nation altering climate without considering global impacts. In Nature Communications last fall, Jones』 team studied the impacts of releasing aerosols in one hemisphere. In short, it would be bad. Releasing aerosols in the Northern Hemisphere could suppress tropical cyclones. Doing the same thing in the Southern Hemisphere would increase their frequency in the north. And both would shift monsoons critical to tropical agriculture.

所有這一切使得研究人員擔心一個流氓國家會因為本國的利益改變氣候，而不考慮對全球影響。在去年秋天的《自然通訊》中，瓊斯的團隊研究了在一個半球釋放氣溶膠的影響。簡而言之，這將是糟糕的。在北半球釋放氣溶膠可以抑制熱帶氣旋。在南半球如果做同樣的事情，也同樣會增加熱帶氣旋在北方的頻率。這兩種情況都將改變季風對熱帶農業的影響。

But if the world ramped up aerosols in a measured way — say, 1 percent of Pinatubo』s sulfur emissions this year, 2 the next, and so on — that might slowly and smoothly even out the rise in temperatures, Caldeira thinks.

但是，如果測量整個世界的氣候改變——比方說，今年排放皮納圖博火山爆發的硫排放量的1%，接下來2%，等等——來增加氣溶膠，那麼這可能會緩慢而平穩地使氣溫上升，卡爾代拉認為。

That still leaves a more human concern, though. In behavioural economics, it』s called a moral hazard: When humans feel protected, we』re more likely to take risks — like driving recklessly after putting on a seat belt. If we see scientists trying to save us, we may stop worrying about greenhouse gases. And geoengineering isn』t a real ix — sulfur only covers up climate change.

不過，最應該關注的還是人類自己的行為。在行為經濟學中，這被稱為道德風險:當人類感到受保護時，我們更有可能去冒險——比如在系好安全帶後魯莽駕駛。如果我們看到科學家試圖拯救我們，我們可能就不再擔心溫室氣體了。而地球工程並不是簡單的離子交換——硫只是掩蓋了氣候變化。

That leaves many climate scientists concerned about overselling geoengineering』s potential. Researchers on Harvard』s SCoPEx team even declined interviews for this piece, saying their project 「gets too much hype.」

這使得許多氣候科學家擔心過度銷售地球工程的潛力。哈佛大學的SCoPEx團隊的研究人員甚至拒絕了對這篇文章的採訪，稱他們的項目「受到了太多的炒作」。

「Will somebody, somewhere, try things? That』s a yes, within 50 or 100 years,」 Wagner says. 「Will it happen as part of a semi-rational climate policy globally coordinated? That』s a bigger question.」?

「有人會去嘗試一些東西嗎?這是肯定的，在50或100年內，」瓦格納說。「這是全球協調的半理性氣候政策的一部分嗎?這是一個更大的問題。」?

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