Solar geoengineering refers to a set of proposed technologies intended to cool the planet by reflecting some incoming sunlight back into space. In recent years, these ideas have gained visibility among a relatively small but influential group of researchers, funders, and commercial actors. Less attention, however, has been paid to the growing and increasingly organised resistance to them. Our research maps that opposition across three actor groups: states and intergovernmental bodies, civil society, and academia.
Among governments and intergovernmental bodies, opposition has emerged at national, regional, and international levels. The African Ministerial Conference on the Environment, representing all 54 African countries, called in 2023 for a global governance mechanism for the non-use of solar radiation management and renewed this position in 2025. Similar concerns were raised during the sixth United Nations Environment Assembly in 2024. Mexico announced a ban on solar geoengineering experiments in its territory in 2023, and Germany’s Federal Environment Agency stated in 2024 that an international non-use agreement should be pursued.
Civil society opposition is also substantial. Indigenous peoples’ organisations, environmental justice movements, grassroots groups, and international NGO networks have long challenged solar geoengineering. The Hands Off Mother Earth Alliance has called for a ban on field experiments and deployment, while the Climate Action Network has opposed deployment and outdoor experimentation. Indigenous resistance organised around the Saami Council was also central to the cancellation of Harvard University’s proposed SCoPEx experiment in northern Sweden.
Academic opposition has likewise become ever more visible. In 2022, an international group of scholars launched an open letter calling for an International Non-Use Agreement on Solar Geoengineering. By January 2026, the letter had been signed by more than 600 academics from 65 countries, spanning a wide range of disciplines. This is the largest academic network publicly opposing solar geoengineering to date.
What explains this widening opposition? Across all three actor groups, solar geoengineering is seen as highly risky and deeply uncertain. It is criticised for failing to address the root causes of climate change and for potentially delaying urgently needed emissions cuts. It is also seen as raising profound questions of justice, legality, and political power, with many critics arguing that it could never be governed in a fair, inclusive, and effective manner over the long timescales deployment would require.
Different actors place different emphases on these concerns. States and intergovernmental bodies often foreground legal obligations, the precautionary principle, and the risk that solar geoengineering could undermine mitigation. Civil society actors more often stress colonial legacies, structural injustice, and violations of the integrity of the Earth. Academic critics frequently highlight governability, geopolitical risk, and the hubris involved in attempting to engineer the planetary climate system. These rationales overlap and reinforce one another, and taken together they make clear that opposition to solar geoengineering is not reducible to a single line of critique.
This matters because it challenges simplistic portrayals of opponents as anti-science or uninformed. Those resisting solar geoengineering are raising substantive questions about risk, justice, legality, and authority. They are not merely reacting from the margins, they are helping to shape the political and normative terrain within which the future of solar geoengineering will be debated and unfold.
As discussions of solar geoengineering continue to expand, so too does contestation over its legitimacy. Taking opposition seriously means recognising that these objections are not peripheral to the governance debate. They are central to it.
This blog is based on a recent article by the authors, “Why oppose solar geoengineering? Mapping and comparing underlying rationales across actor groups” published in Climatic Change.