This summer, Harvard researchers working on a project called Scopex were supposed to fly a literal trial balloon over Sweden. This would have been the first step toward testing a potential method to moderate global warming by releasing small quantities of particles into the atmosphere. Early on, Harvard established an independent advisory committee to provide advice on the science and risks of the proposed experiment, as well as on the need for stakeholder engagement. Recently, however, the Swedish Space Corporation canceled the flight in the wake of opposition from Swedish environmentalists, scientists, and indigenous groups, even though the first flight would have involved no experimental release of particles.
Unprecedented wildfires, storms, and floods make it clear that climate change has arrived. And as climate change worsens, there is growing interest in researching solar geoengineering—a cluster of proposed strategies for reflecting sunlight to reduce the Earth’s warming. For instance, Congress has begun to provide modest funding for modeling and observing stratospheric conditions potentially relevant to solar geoengineering proposals.
The Scopex researchers, who are privately funded, have expressed support for suspending test flights to allow for robust public engagement, and the experiment may still go forward. Nonetheless, the recent cancelation demonstrates that we need more public engagement on solar geoengineering research. Opponents of the Swedish test flights appear more worried about where this research might lead than about any individual test flight—and those worries can’t be ignored. Solar geoengineering research cannot succeed without robust governance and public engagement.
Two of the leading solar geoengineering proposals are stratospheric aerosol injection (to which Scopex is relevant) and marine cloud brightening. Inspired by the cooling effects observed after major volcanic eruptions, stratospheric aerosol injection would attempt to reflect incoming sunlight by distributing small particles high in the atmosphere. Marine cloud brightening, which is patterned after the “tracks” formed when water vapor condenses on particles in ship exhaust, would seek to increase the reflection of sunlight by low-lying clouds.
Those are the goals—but solar geoengineering strategies are not well understood. Each proposed technique comes with substantial questions of feasibility. For stratospheric aerosol injection, these questions include: Which materials should be used and in what quantity? Where and how should materials be released? And what happens to materials after they are released? For marine cloud brightening, the questions include: How do tiny particles interact with clouds? How might clouds be modified to reflect more light? And in what regions might this technique be effective? Researchers also know little about potential impacts on health, ecosystems, and society. Might solar geoengineering reduce crop yields, interfere with Asian and African monsoons, harm biodiversity, or hamper solar energy production?
The many questions surrounding solar geoengineering —including those we haven’t even thought to ask yet—underscore the need for a broad inquiry into its social, political, economic, and scientific dimensions. Yet such research itself raises further questions. What role should the public have in research processes, especially in outdoor experiments that could affect human populations? Might research create momentum for solar geoengineering and lead to deployment before it is appropriate? And could research undermine efforts to reduce greenhouse gas emissions by offering the misleading prospect of a quick and easy solution to climate change?
The concerns associated with solar geoengineering, the controversy raised by outdoor experiments like Scopex, and the planetary implications of solar geoengineering all point to the need for governance of solar geoengineering research. In this context, the National Academies of Sciences, Engineering, and Medicine established a committee, on which I served, to develop a research agenda and recommend research governance approaches for solar geoengineering. Our recent report sets out recommendations geared toward facilitating the production of knowledge to reduce scientific and social uncertainties regarding solar geoengineering.
One key recommendation calls on the federal government, in coordination with other countries, to establish a transdisciplinary solar geoengineering research program that would develop knowledge to inform policy makers. At the same time, we also recommend that all solar geoengineering research be subject to robust governance—which is not the same thing as government. Funders of research, publishers of scientific journals, professional societies, international organizations, and solar geoengineering researchers themselves all have a role to play in attending to the physical and societal risks of research, fostering transparency, and enabling public engagement.
Mechanisms to govern solar geoengineering research should include permitting requirements for outdoor experiments, impact assessment and review processes, a research registry, public engagement efforts, and adherence by researchers and research sponsors to a code of conduct. Public engagement could take the form of citizen consultations in which nonexperts at various locations debate the same policy-related questions pertaining to solar geoengineering and individually vote for prepared answers to the questions posed. Code of conduct provisions should include commitments to make research activities and results public and to monitor and minimize potential adverse effects of research. Furthermore, ongoing programmatic assessment of solar geoengineering research can evaluate the cumulative impacts of multiple experiments, consider the overall trajectory of research activities, and guard against the entrenchment of ineffective or dangerous technologies.
All of that will take time, money, and commitment. Unfortunately, the worsening impacts of climate change will only increase pressures on policy makers to consider solar geoengineering.
Robust governance is necessary both to facilitate solar geoengineering research and to curb its risks. Adherence to recommended procedures and limits on outdoor experiments can reduce physical risks. Transparency regarding the capabilities and limits of solar geoengineering can counter the potential for solar geoengineering research to detract from other climate efforts. And broad public engagement can improve the quality of research while building the social license to enable the research.
Ignoring solar geoengineering will not make it—or climate change—go away. Research—and robust governance of that research—are essential to making informed decisions about it.