Who Decides on Solar Geoengineering? Researchers Map the Justice Terrain

A trio of researchers argues that the loudest debates about solar geoengineering have been asking the wrong question. Rather than fighting over whether deliberately cooling the planet would produce a just outcome, they say, scientists, ethicists, and policymakers should be scrutinizing the justice of the processes and practices through which any decision about these technologies would actually be made. The argument, laid out in an essay by Sikina Jinnah, Portia Adade Williams, and Catriona McKinnon published in the journal PLOS Climate, offers a reframing that could reshape how the world thinks about one of the most controversial climate interventions on the horizon.

Solar geoengineering refers to a set of emerging technologies that would seek to cool the planet by reflecting a small fraction of incoming sunlight back into space. The most widely discussed approach, stratospheric aerosol injection, would scatter reflective particles high in the atmosphere to lower global temperatures temporarily. Proponents point out that such techniques might reduce the worst impacts of climate change while humanity works to cut greenhouse gas emissions. Critics counter that the technologies carry serious risks of their own, including the possibility of technological lock-in, in which societies become dependent on continued deployment, and mitigation deterrence, in which the prospect of a technological fix weakens the political will to reduce emissions in the first place.

It is precisely because the potential benefits and dangers are so entangled that questions of justice and ethics sit at the center of the debate, the authors contend. Who would bear the risks of deployment? Who would benefit? Who gets a voice in deciding? Many scholars have responded to these questions by asserting a clear justice landscape, mapping out in advance which interventions would be fair and which would not. Jinnah, Williams, and McKinnon take a different view. In their essay, they argue that the terrain is complicated, nuanced, and not fully mapped, and that pretending otherwise risks closing down conversations before they have properly begun.

To illustrate that complexity, the essay explores three core narratives at the intersection of solar geoengineering and justice. The first is intergenerational ethics, the question of what present generations owe to future ones. Solar geoengineering is distinctive among climate responses because its effects would be temporally extended in unusual ways. A deployment program might need to continue for decades or longer, and termination could bring rapid temperature rebounds with severe consequences for people who had no say in the original decision. Future generations, in other words, would inherit both the climate consequences and the governance commitments of choices made today, yet they cannot participate in any deliberation. That asymmetry complicates any simple claim that deploying or refusing to deploy the technology is straightforwardly just.

The second narrative concerns participatory justice, the demand that those potentially affected by a decision have a genuine opportunity to shape it. Solar geoengineering poses an acute version of this problem because its impacts would be global while its governance, at least initially, is likely to be controlled by a small number of states, institutions, or even private actors with the technical capacity to act. Meaningful participation across nations with vastly different resources, vulnerabilities, and scientific capacities is extraordinarily difficult to design. Yet the authors suggest that the difficulty of achieving perfect participation should not be treated as a reason to abandon the effort. Instead, the quality of the participatory process itself becomes a central object of ethical scrutiny.

The third narrative involves recognitional and reparational justice. Recognition asks whether the identities, values, and knowledge systems of different communities, particularly those historically marginalized in international environmental politics, are respected in the debate. Reparation asks whether past injustices, including the unequal historical responsibility for greenhouse gas emissions and the colonial legacies that shape global science and governance, are acknowledged and addressed. For many countries in the Global South, solar geoengineering raises the specter of yet another arena in which powerful actors make decisions with planetary consequences while the most vulnerable communities absorb the risks. Williams, whose work engages climate governance in Africa, brings that perspective to bear on an argument that justice claims in this space cannot be evaluated in the abstract but must reckon with these historical patterns.

What unites the three narratives is the authors’ conclusion that the field has been too focused on outcomes and not focused enough on procedures. Debates about solar geoengineering often proceed as if the central question were whether a given deployment scenario would produce a net benefit for humanity, a calculation that could in principle be settled by models and impact assessments. The essay pushes back against that framing. If the terrain of justice is genuinely unmapped, then certainty about just outcomes is premature, and the ethical weight shifts to how research, deliberation, and any eventual decisions are conducted. Are the practices governing experimentation transparent? Do they include the people whose lives would be most affected? Are they designed in ways that remain accountable over the long time horizons the technology would demand?

This procedural turn has practical implications. It suggests that early governance choices, such as norms around research funding, transparency requirements for outdoor experiments, and the inclusion of diverse voices in advisory bodies, are not merely administrative preliminaries to the real debate. They are the real debate, because they establish the practices within which all later decisions will be made. A governance architecture that embeds participation, recognition, and accountability from the start could make even a decision to ban solar geoengineering more legitimate, just as a closed and exclusive process could delegitimize even a well-intentioned research program. The authors argue that focusing on just processes and practices for technological innovation and governance could enhance the capacity to co-create a world where any decision on solar geoengineering, whether to ban it or move it forward, rests on thoughtful, ethical, and participatory decision-making that speaks to the interests of all people potentially affected.

The essay also carries a message for the research community. Much of the existing scholarship on geoengineering ethics has sought to adjudicate between competing justice claims, effectively drawing boundaries around what a just position would look like. Jinnah, Williams, and McKinnon instead call for humility about the limits of current understanding. The justice landscape, on their account, is not a finished map waiting to be consulted but a territory still being charted, one in which new voices, new impacts, and new institutional arrangements could shift the ethical calculus. That humility does not mean paralysis. It means treating deliberation itself as an ongoing practice whose quality matters as much as its conclusions.

As interest in solar geoengineering research grows, with modeling studies, small-scale experiments, and governance proposals multiplying across universities and international bodies, the questions raised by the essay are becoming more urgent. The technology could temporarily lower global temperatures and reduce some of the worst impacts of climate change, but it could also entrench dependence, weaken mitigation, and concentrate power in the hands of a few. Whether it is ultimately banned, deployed, or left untested, the decision will be one of the most consequential humanity has faced. The authors’ argument is that the measure of that decision’s legitimacy will lie less in the outcome it produces and more in the fairness of the process that produced it, a standard that demands attention now, long before any thermostat for the planet is touched.

Subject of Research: Justice and ethics in solar geoengineering governance

Article Title: Mapping justice claims for solar geoengineering

Article References: Jinnah, S., Williams, P. A., & McKinnon, C. (2026). Mapping justice claims for solar geoengineering. PLOS Climate, 5(9), e0001054. https://doi.org/10.1371/journal.pclm.0001054

Image Credits: AI Generated

DOI: 10.1371/journal.pclm.0001054

Keywords: solar geoengineering, climate governance, intergenerational ethics, participatory justice, recognitional justice, reparational justice, stratospheric aerosol injection, mitigation deterrence, technological lock-in, PLOS Climate, climate ethics, global south