Solar geoengineering rises in the East - 節選
The year is 2040 and the planet is hot, more than 1.5 degrees Celsius warmer on average than before the start of the Industrial Revolution. Residents of coastal cities are retreating to higher ground as rising tides encroach on their neighbourhoods. Summer has become synonymous with extreme heat waves in Eastern China and violent floods along the Yangtze River. To mitigate further catastrophe, China and other world powers decide to dim the sun. 2040年的地球很熱——平均氣溫比工業革命前高1.5攝氏度。由於家園被不斷上漲的潮水侵蝕，沿海城市的居民正向更高的地方撤退。夏季已經成為中國東部極端熱浪和長江沿線洪水肆虐的代名詞。為了緩解災難的進一步惡化，中國和其他大國決定想辦法遮蔽太陽光。
Once limited to the realm of science fiction, scientists are now considering how to engineer the climate to avert the worst impacts of global warming. 這曾是科幻小說中的場景，但現在科學家們正在考慮如何管理氣候，以避免全球變暖帶來的最嚴重的影響。
Geoengineering has entered mainstream scientific debate in recent years as the window to reduce greenhouse gas emissions narrows. A draft report by the United Nations Intergovernmental Panel on Climate Change (IPCC) shows that by 2040 the global average temperature is projected to exceed 1.5 degrees Celsius above pre-industrial levels. This is the threshold established by the Paris Agreement after which the risk of catastrophic climate impacts increases. 近年來，隨著減少溫室氣體排放的機會愈發渺茫，地球工程已經成為主流科學辯論的議題。聯合國政府間氣候變化專門委員會（United Nations Intergovernmental Panel on Climate Change ，以下簡稱IPCC）撰寫的一份報告草案顯示，到2040年全球平均氣溫預計將上升超過1.5攝氏度——這是《巴黎協定》規定的溫升限值，一旦超過，出現災難性氣候影響的風險將大大增加。
If it proves feasible, geoengineering could buy nations some time to decarbonise by temporarily turning down the global thermostat and slowing the impacts of climate change. However, critics argue that even researching it creates a moral hazard because it sends a false signal to the public that a hitherto unproven technological fix can be relied on. 如果證明可行，地球工程可以通過暫時關閉全球恆溫調節機制以及減緩氣候變化的影響，為各國贏得一些脫碳的時間。然而批評者認為，即便是研究這個話題也會產生“道德風險”，向公眾發出錯誤信號，讓他們認為可以依靠目前尚未證實的技術來修復氣候變化。
China is more vulnerable than most countries to extreme weather events linked to a changing climate. The government is focusing on reducing emissions by decarbonising the economy, but it has also launched a research programme to study geoengineering’s potential to mitigate climate change. Although it is still in its infancy, the three-year-old programme raises the question of whether China would deploy solar geoengineering.中國比大多數國家都更容易受到氣候變化相關極端天氣事件的影響。中國政府目前正集中力量通過推動經濟去碳化來減少排放，但3年前中國政府還啟動了一個項目，研究地球工程在減緩氣候變化方面的潛力。儘管該項目仍處於起步階段，但卻讓人們對於中國是否將部署太陽能地球工程的問題提出了質疑。
Uncharted territory
未知領域
Geoengineering involves the deliberate, large-scale intervention in the Earth’s natural systems to counteract climate change. It works in two main ways: blocking sunlight and sucking carbon dioxide out of the atmosphere. Scientists in China have largely focused on techniques to block the sun because they offer the potential to rapidly cool the planet. But they pose risks that require careful study. 地球工程是指人類主動大規模干預地球自然系統以抗擊氣候變化的活動，主要有兩種方式：阻擋太陽光和吸收大氣中的二氧化碳。中國科學家大多專注於研究阻擋陽光的技術，這種技術為迅速降低地球溫度提供了可能，但隨之而來的風險還需仔細研究。
Solar geoengineering is untested but volcanic eruptions are a natural analogue for one approach. The 1991 eruption of Mount Pinatubo in the Philippines released sulfur dioxide into the atmosphere that formed sulfate aerosols. These scattered sunlight to the extent that the Earth cooled by around 0.4 degrees Celsius from 1992-1993. Scientists have proposed replicating the volcano effect by spraying aerosols out of specially equipped planes at 70,000 feet. 太陽能地球工程還沒有經過測試，但火山爆發卻是對阻擋太陽光這種方式的一種自然模擬。1991年菲律賓皮納圖博火山爆發向大氣中釋放了二氧化硫，形成硫酸鹽氣溶膠，一定程度上導致太陽光的散射，因此1992至1993年間地球溫度下降了約0.4攝氏度。科學家們建議用配有特殊裝置的飛機在7萬英尺的高空噴灑氣溶膠，來複制這種火山效應。
This could quickly cool the planet, but it would not target the greenhouse gases that are the source of the problem. The atmosphere would not return to a pre-industrial state because carbon dioxide would continue to acidify the ocean and have other effects on ecosystems. While carbon dioxide removal technologies could, in theory, be employed simultaneously to draw the accumulated gases out of the atmosphere, these technologies are also only just being piloted and face significant barriers. 這種方法能讓地球迅速降溫，但終究沒有解決溫室氣體這一問題的根源所在。大氣不會回到工業革命前的狀態，二氧化碳將繼續造成海洋酸化，並且對生態系統產生其他影響。雖然從理論上講，可以同時採用二氧化碳清除技術吸收大氣中的二氧化碳，但這些技術也只處於試行階段，面臨著巨大的障礙。
Choosing between risks
權衡風險
Solar geoengineering is “insane” according to John Moore, a British scientist at Beijing Normal University (BNU) who leads China’s geoengineering research programme. 北京師範大學英國籍教授、中國地球工程研究項目主持人約翰·摩爾說，太陽能地球工程太“瘋狂”。
“The only sane solution is to stop burning fossil fuels,” he says. “唯一理智的解決辦法就是停止化石燃料燃燒，”他說。
Moore’s sentiment is common among those researching the topic. Concerns range from discomfort about playing a god-like role by tinkering with the climate to fears of inadvertently developing a weaponisable technology. Nonetheless, scientists pursue this research under the hypothesis that the risks posed by solar engineering may be less grave than those posed by a rapid temperature rise – under current government commitments, the United Nations Environment Programme projects the world is set to warm by at least 3 degrees Celsius by the end of the century. 摩爾的觀點在這一課題的研究人員中很常見，他們有的人對扮演上帝一樣的角色去修補氣候感到不適，有的則害怕自己會在不經意間研發出可以用做武器的技術。然而，科學家們的研究是以太陽能地球工程造成的風險可能遠小於快速升溫的風險這個假設為前提的。根據聯合國環境規劃署的預測，按照目前各國政府承諾的減排量，到本世紀末全球溫度將上升至少3攝氏度。
Solar geoengineering is known to pose myriad health and environmental risks, from decreased rainfall to heightened skin cancer rates due to ozone depletion. 眾所周知，太陽能地球工程會帶來許多健康和環境風險，包括降雨減少，以及臭氧耗竭導致皮膚癌發病率增高。
The severity of these risks would depend on the degree of solar geoengineering deployed. Changes in Asia’s monsoon precipitation, for instance, would be minimal under a moderate deployment scenario whereas precipitation could be reduced significantly if solar geoengineering were to offset all global warming. 這些風險的嚴重性將取決於太陽能地球工程的部署程度。例如，如果只是適度部署，亞洲季風降水量的變化將非常小，但如果太陽能地球工程的部署規模大到足以抵消所有全球變暖，降水量就會大大減少。
These are some of the known risks, but Moore warns of “unknown unknowns”. 這些都是已知的風險，但摩爾提醒要注意“未知的未知數”。
The Chinese research programme is investigating the risks and potential impacts. It is funded by a 17 million yuan (US$3 million) grant from the Ministry of Science and Technology. The team of over thirty researchers has focused on governance issues and computer modelling to understand geoengineering’s impacts, particularly on China. One of their studies, for instance, models how sulfate aerosol injection could slow the melting of the Himalayan glaciers, which are key to China’s water security. 中國的研究項目正在調查太陽能地球工程的風險和潛在影響，該項目由國家科技部資助，研究經費達1700萬元人民幣。30多名科研人員組成的團隊重點研究治理問題，並通過電腦建模理解地球工程的影響，尤其是對中國的影響。例如，其中一項研究模擬了向大氣層噴射硫酸鹽氣溶膠將如何讓處於不穩定狀態的喜馬拉雅冰川融化得慢一些，而這些冰川的安危事關中國的水安全。
The lead Chinese scientist on the team, Cao Long, an Earth sciences professor at Zhejiang University and one of China’s IPCC report authors, is careful to distinguish research from deployment. 項目首席中國科學家、浙江大學地球科學教授、中國IPCC報告作者之一的曹龍很謹慎地把研究和部署區分開來。
“Doing this research does not mean that we will definitely implement geoengineering in the future,” he says. “The research itself has scientific value.” “我們做這個研究不代表我們以後就一定要實施地球工程，但是對這個研究本身是有意義的” ”他說。
Flying close to the sun
飛向太陽
While researchers in China focus on modelling impacts, scientists at Harvard University are preparing for the first solar geoengineering field experiments in the stratosphere as part of a privately-funded US$20 million project. 就在中國研究人員專注於通過建模研究地球工程的影響時，哈佛大學的科學家們正準備開始首次平流層太陽能地球工程實驗，此次實驗是一個由私人出資2000萬美元建立的項目的一部分。
This year, they plan to launch a balloon fitted with measurement equipment into the stratosphere over Arizona. For the first experiment, the balloon will release ice into the atmosphere to study the resulting microphysics. But eventually Harvard scientists may release sulfates to study the geoengineering approach exhibited after the Mt Pinatubo eruption. 今年，他們計劃向亞利桑那州上空發射一個裝有測量設備的氣球。首次實驗中，氣球會向大氣中噴灑冰晶，並從微觀物理學的角度研究由此產生的一系列影響。但哈佛的科學家們最終可能會向平流層噴灑硫酸鹽，從而研究皮納圖博火山噴發後呈現的地球工程方法。
This experiment falls within international guidelines for geoengineering field experimentation established under the UN Conference for Biological Diversity (CBD). The guidance permits small-scale field studies “subject to a thorough prior assessment of the potential impacts on the environment”. 這個實驗符合聯合國生物多樣性會議制定的地球工程野外實驗國際指南，該指南允許進行小規模的野外研究，“但須事先對潛在的環境影響進行徹底評估。”
Will China follow? Moore says that some Chinese scientists have expressed interest in field experimentation to build on their modelling results. However, Cao Long, who recently co-authored a paper on cutting-edge “cocktail geoengineering” – combining multiple solar geoengineering solutions – said the concepts remain theoretical.“I think the majority of our research in the next two to three years will definitely be focused on computer modelling because the risks of field experiments are too great,” he says. 中國會效仿嗎？摩爾說一些中國科學家已經表示有興趣在建模結果的基礎上進行野外實驗。曹龍最近與他人合作撰寫了一篇關於 前沿“雞尾酒地球工程”，也就是結合多個太陽能地球工程解決方案的文章。然而，他認為這些概念仍是理論上的。“我認為，未來近期數年內地球工程研究都會通過氣候模式模擬進行， 因為野外實驗的風險太大了。”
David Keith, one of the scientists leading Harvard’s experiments, says that field experiments can help scientists refine their models and improve their understanding of risks. For experiments like Harvard’s that pose no physical risks, Keith says his support for such studies would be unlikely to change in the Chinese context. He sees them as an essential part of the scientific process. But critics argue that if experiments show minimal risks, they could make deployment more likely.哈佛大學實驗的領銜科學家之一大衛·基思說，野外實驗可以幫助科學家修正自己的模型，增強他們對風險的理解。如果中國要做的是哈佛大學做的這種沒有任何實質性風險的野外研究，基思說，他依然會持支持態度。他認為這類研究是科學進程的一個重要部分。但批評人士認為，實驗如果證明地球工程的風險非常小，就會增加其部署的可能性。
A thorny governance problem
棘手的治理問題
A comprehensive global governance regime to manage the development and use of solar geoengineering is still in its early stages. 管理太陽能地球工程的發展和使用的全球綜合性治理機制還處於起步階段。
Chen Ying, a project coordinator in China’s research programme focused on governance, says that at this stage, “governance is to guard against the abuse of the technology, not to facilitate implementation.” 專注治理問題的中國研究項目研究人員陳迎表示，在現階段“治理的目的在於防止技術濫用，而不是為了促進實施。”
Solar geoengineering could be inexpensive enough for a single country or wealthy individual to go it alone for a number of years. To minimise this risk, the Carnegie Climate Geoengineering Governance Initiative is encouraging countries to agree not to deploy solar geoengineering until the risks and benefits are sufficiently known and a governance system has been established. To start this process the Carnegie Initiative is advocating for countries to introduce a resolution in the UN Environment Assembly in 2019. 太陽能地球工程的成本可以很低，一個國家或者富裕的個人都能夠獨立運營數年。為了儘量降低風險，“卡內基氣候地球工程治理倡議”（Carnegie Climate Geoengineering Governance Initiative）鼓勵各國達成一致，在沒有充分了解風險和效益以及建立治理系統之前，不部署太陽能地球工程。為了推進這一議程，“卡內基倡議”提倡各國在2019年聯合國環境大會上提出一項決議。
But what shape might governance take? “This will be the most global thing humanity has ever done if we ever get there, and therefore, it will require a kind of global solution that we just don’t have on the table right now,” says Janos Pasztor, the director of the Carnegie Initiative. 但治理會採取何種形式呢？“如果真的到了這一步，那這將是人類所做過的最為全球性的事情，需要採取我們目前還沒有的全球性解決方案，”“卡內基倡議”主管扎諾斯·帕茲託說。
Given the need to deter high-risk experiments, he sees parallels with nuclear non-proliferation. Of course, geoengineering is intended to be a solution to a global problem, not a weapon. A set of governance principles designed by Oxford academics suggest that it be governed as a public good with tight controls on commercialisation as technologies develop. Moving from these concepts to a formalised global governance structure would likely take decades, according to Pasztor. 鑑於有必要遏制這類高風險的實驗，帕茲託認為需要採取與防止核擴散相類似的手段。當然，地球工程的目的是解決全球性的問題，而不是成為武器。牛津大學學者設計的一套治理原則建議，應該將地球工程作為一項公共物品來治理，需在技術發展過程中嚴格控制其商業化。從這些概念發展到正式的全球治理框架可能需要數十年時間，帕茲託說。
If solar geoengineering were deployed then long-term stable management would also be needed to ramp it up and down gradually. Otherwise there is a risk of “termination shock” whereby global temperatures snap back rapidly, with potentially devastating impacts on ecosystems. 若要部署太陽能地球工程，就需要對其進行長期穩定的管理來逐步調整其強度，以防止發生“邊界激波”的風險，即全球氣溫迅速下降，可能會對生態系統造成災難性的影響。
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