샌프란시스코의 비영리단체 '리플렉티브(Reflective)'가 성층권 에어로졸 주입(SAI) 연구 로드맵을 발표했습니다. 이 로드맵에 따르면 조율된 연구 진행 시 약 10년과 3억 7천만 달러가 소요되며, 그렇지 않으면 20년과 14억 달러가 필요합니다. 야외 실험 필요성을 주장하는 이 보고서는 강력한 기술의 거버넌스 문제를 이유로 야외 실험 금지를 촉구하는 학계의 반발에 직면해 있어, 기후 기술 정책 방향을 가늠할 중요한 분수령이 됩니다.
번역된 본문
MIT 테크놀로지 리뷰가 확인한 바에 따르면, 샌프란시스코의 한 비영리단체가 태양 지구공학 사용 여부에 대해 정보에 입각한 결정을 내리는 데 필요한 실험, 연구, 인프라에 대한 상세한 로드맵을 발표했습니다. 과학자들은 화산 분출의 냉각 효과를 모방해 성층권에 반사성 입자를 방출함으로써 기후변화를 상쇄할 수 있다는 가능성을 반세기 동안 탐구해 왔습니다. 하지만 성층권 에어로졸 주입(SAI)으로 알려진 이 개념에 대해 최소한 수백 건의 연구가 이루어졌음에도, 그 효과와 부수적 영향에 대한 과학적 이해에는 큰 공백이 남아 있으며, 이러한 불확실성을 해소하기 위한 체계적인 계획은 지금까지 없었습니다.
태양 지구공학 연구에 자금을 지원하는 연구기관인 리플렉티브(Reflective)는 오늘 SAI 연구 로드맵을 발표하며 이 공백을 메우고자 했습니다. 이 단체의 공동창립자이자 최고경영자인 다코타 그루너는 "우리의 사명은 세계가 의미 있는 시기 내에 햇빛 반사에 관한 정보에 입각한 의사결정에 필요한 데이터와 도구를 갖추도록 돕는 것"이라며 "세계가 우리의 연구 체계가 준비된 것보다 훨씬 짧은 시간 안에 매우 중대한 결정을 내려야 할 수 있다는 것이 우리의 판단"이라고 말했습니다.
그루너에 따르면, 이 로드맵이 과학적 노력을 이끌고 재단이나 정부 기관이 우선순위가 높은 연구에 자금을 지원하며 '책임 있게 연구를 가속'하도록 장려하기를 바란다고 합니다. 보고서는 모든 작업이 조율된 방식으로 수행되면 약 10년과 약 3억 7천만 달러가 소요되고, 그렇지 않으면 대략 20년과 거의 14억 달러가 필요할 것으로 추정했습니다.
그루너는 리플렉티브가 이 형태의 태양 지구공학 사용을 옹호하는 것은 아니라고 강조하지만, 이 보고서는 성층권에 점점 더 많은 양의 이산화황(또는 이를 전환시키는 물질)을 방출하며 무슨 일이 일어나는지 관찰하는 야외 실험의 필요성을 주장하고 있습니다. 이는 논쟁적인 입장입니다. 2002년 이후 수백 명의 학자들이 야외 실험 금지와 '국제적 비사용 협정'을 촉구하는 공개 서한에 서명해 왔으며, 이처럼 강력한 기술은 결코 전 세계적으로 공평한 방식으로 통제될 수 없다고 주장합니다. 일부 서명자들은 더 많은 연구가 태양 지구공학 사용에 관한 가장 큰 질문 중 하나, 즉 '누가 이를 수행할 수 있는가'를 결코 해결할 수 없다고 주장합니다.
비사용 운동의 공동 발기인이자 네덜란드 바헤닝언 대학의 글로벌 환경 거버넌스 교수인 아르티 굽타는 최근 무대 인터뷰에서 "내 관점에서 1차적인 질문은 기술적인 것이 아니다"라며 "핵심 질문은 성층권 에어로졸 주입과 같은 지구를 변화시키는 기술을 누가 통제할 것인가 하는 것이다. 누가 개발하고, 누가 배치하며, 어떤 목적으로? 어떤 목적을, 누구의 목적을 위해 봉사하는가? 이 질문들은 매우 근본적이다. 왜냐하면 이 지구를 변화시키는 기술에는 수혜자와 피해자가 생기기 때문"이라고 말했습니다.
'의미 있을 만큼 빠르게'
그루너가 2023년 말 리플렉티브를 설립한 이후, 이 비영리단체는 태양 지구공학 연구 분야의 중요한 주체로 빠르게 부상했습니다. 여러 저명한 자선단체와 개인으로부터 2천만 달러 이상을 모금했으며, 수십 개 연구 그룹에 약 400만 달러를 지원했습니다. 리플렉티브는 오픈소스 태양 지구공학 시뮬레이터 개발과 공동 연구를 위한 온라인 허브 구축 등 연구 촉진을 위한 자체 프로젝트도 몇 개 수행했습니다.
올해 초 리플렉티브는 SAI 불확실성 데이터베이스를 공개했으며, 이는 소규모 태양 지구공학 노력조차 진행되기 전에 해결해야 할 긴 목록의 과학적 미지수와 공학적 장애물을 식별했습니다. 가장 큰 불확실성 중 일부는 어떤 기체나 입자를 사용하는 것이 가장 합리적인지, 그리고 건조한 성층권에 방출되면 무슨 일이 일어날지에 관한 것입니다.
A San Francisco nonprofit has published a detailed road map of the experiments, studies, and infrastructure that it says would be needed to make informed decisions about the use of solar geoengineering, MIT Technology Review can reveal. Scientists have now spent half a century exploring the possibility that we could counteract climate change by releasing reflective particles into the stratosphere, mimicking the cooling effects of volcanic eruptions. But even after at least hundreds of studies on the concept, known as stratospheric aerosol injection (SAI), big gaps remain in the scientific understanding of how well it would work and what else it might do—and there has been no systematic plan for clearing up that uncertainty. Reflective, a research organization that funds studies on solar geoengineering, has today attempted to fill that gap with the release of its SAI Research Roadmap . “Our mission is to equip the world with the data and tools required for informed decision-making about sunlight reflection fast enough to matter,” says Dakota Gruener, the organization’s cofounder and chief executive. “Our sense is the world may need to make very consequential decisions on timelines far shorter than our research system is prepared for.” The hope is the exercise will guide scientific efforts and encourage philanthropies or government agencies to fund high-priority work and “responsibly accelerate research,” says Gruener. If all the work is done in a coordinated way, it would take about a decade and cost around $370 million—and if it’s not, it would require roughly 20 years and nearly $1.4 billion, the report estimates. While Gruener stresses that Reflective doesn’t advocate using this form of solar geoengineering, the report does make the case for conducting outdoor experiments, which would release successively larger amounts of sulfur dioxide (or materials that would convert into it) in the stratosphere to observe what happens. That is a controversial standpoint. Since 2002, hundreds of academics have signed an open letter calling for a ban on outdoor experiments and an "international non-use agreement," arguing that such a powerful technology could never be governed in a globally equitable way. And some signatories argue that more studies can never address one of the biggest questions about using solar geoengineering: Who gets to do it. “The first-order questions, from my perspective, are not technical,” Aarti Gupta, co-initiator of the non-use initiative and professor of global environmental governance at Wageningen University in the Netherlands, told me in a recent on-stage interview . “The core question is: Who would control a planet-altering technology like stratospheric aerosol injection? Who would develop it, and who would deploy it, and to what end? To serve what purposes, and whose purposes? Those questions are very fundamental, because this planet-altering technology will have winners and losers.” ‘Fast enough to matter’ Since Gruener incorporated Reflective in late 2023, the nonprofit has quickly become an important player in solar geoengineering research. It has now raised more than $20 million from a number of prominent charities and individuals, and it’s provided around $4 million to several dozen research groups. Reflective has also undertaken a handful of its own projects to promote research, including the development of an open-source solar geoengineering simulator and an online hub for collaborative research. Earlier this year, Reflective released its SAI Uncertainties database , which identified a long list of scientific unknowns and engineering obstacles that would need to be addressed before even a small-scale solar geoengineering effort could move ahead. (I wrote about the specific scenario and the unknowns in this earlier piece .) Some of the biggest uncertainties involve what gas or particles would make the most sense to use and what would happen once they were released in the dry stratosphere. It’s not clear, for example, whether they’d spread out in a way that maximizes the reflectivity—or clump together and quickly fall out into the troposphere, the lowest layer of Earth’s atmosphere. The road map builds upon the database, highlighting the path to addressing most of those questions. The road map The initial phase in Reflective’s road map, labeled “foundational knowledge,” includes additional computer simulation studies and lab experiments designed to shed light on the potential impacts on different regions, ecosystems, and phenomena, including ocean circulation patterns, ice sheets, and crop yields. The report also notes the need to begin developing more observational tools during this phase to improve understanding of the baseline conditions of the stratosphere—and, in turn, our ability to assess any effects from the eventual release of materials. This first stage would last two to three years and cost $30 million to $75 million, though some of the analysis and observational work would continue into subsequent phases. The next stage would include using modified aircraft to release 10 metric tons of sulfur dioxide into the stratosphere, four times over the course of two seasons. The full research stage could take four to eight years and cost $70 million to $150 million, the report says. The work during it may reduce uncertainty about the “cooling efficacy” of solar geoengineering, or how much the planet would cool per ton of sulfur released, by about 25%. The experiments during the next phase would step those levels up dramatically, releasing 25,000 tons of sulfur dioxide over the course of one season, at least once but possibly twice. That research stage, which includes other work as well, would last four to 11 years, run $270 million to $1.1 billion, and decrease efficacy uncertainty by around 66%, according to the road map. The final phase of research would be ongoing monitoring of full-scale solar geoengineering, if the world goes ahead with it. The goal would be to gather real-life data on the technology in action, update estimates of the effects in models, and spot any “unexpected or undesired consequences.” Gruener says that the road map is intended as a Version 1, meant to be “concrete enough for people to argue with.” But Reflective intends to update the plan as it receives additional reactions from researchers and other observers, and it will invite such feedback through a mechanism on the site. She also notes that there are firm “stage gates,” set up between the latter stages—in other words, research shouldn’t proceed to the next phase if the experiments suggest that the releases don’t have the hoped-for impact, show worrisome downsides, or fail to resolve crucial uncertainties. “Our road map has these gates precisely because there may be points where the answer is ‘You should stop,’” she says. Termination shock Most observers I spoke to about the report agree that these studies could reduce uncertainty about the effectiveness of solar geoengineering and our technical ability to carry it out. But highlighting the scientific importance of outdoor experiments won’t necessarily make them any easier to move ahead with. Several earlier proposals to carry out such experiments, including Harvard’s SCoPEx and the UK-based SPICE project , were ultimately halted amid opposition from environmentalists or policymakers . In addition, not everyone agrees that experiments at those scales will get us to the point where we’re capable of making an “informed decision.” Wil Burns, a research professor and legal scholar at American University and a signatory to the International Non-Use Agreement, fears that scientists won’t be able to understand the extent of the potential downsides, including impacts on the protective ozone layer and changes to regional precipitation patterns, until we’re carrying out full-fledged solar geoengineering. “The research would give you some answers,” he says. “I just don’t think it gives you answers that