Solar geoengineering: growing scientific and political support for a non-use agreement

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Growing momentum for a solar geoengineering non-use agreement, driven by Global South governments and civil society, aims to prevent risky distractions from the urgent fossil fuel phaseout, says Prof Aarti Gupta of Wageningen University, the Netherlands.

Published on September 24th, 2025

Global resistance to the development and potential use of solar geoengineering technologies is rapidly intensifying. In a striking recent political development, the 2025 African Ministerial Conference on the Environment (AMCEN) —a biennial meeting of African environment ministers—unequivocally rejected solar geoengineering as a response to climate change (1). Environment ministers from across the continent called for a “non-use agreement on solar geoengineering” (2), noting their “unequivocal rejection of stratospheric aerosol injection and other forms of solar geoengineering as unacceptable climate solutions, given their significant environmental, ethical and geopolitical risks” (2).

These concerns echo the many risks and dangers that geoengineering poses for the polar regions, as comprehensively and systematically examined in the Siegert et al.’s (3) Frontiers in Science lead article Safeguarding the polar regions from dangerous geoengineering: a critical assessment of proposed concepts and future prospects, which has been co-authored by 42 scientists.

They also align with the 2022 academic initiative calling for an International Non-Use Agreement on Solar Geoengineering, of which I am a co-initiator and signatory. This initiative opposes the development and use of solar geoengineering (also called solar radiation modification), notably stratospheric aerosol injection. An Open Letter at its core calls upon governments, the United Nations (UN) and other actors to commit to five elements of non-use:

Not to deploy solar geoengineering technologies

Not to allocate public funding for research that leads to technology development

Not to allow outdoor experiments on their territory

Not to grant patent rights for solar geoengineering technologies

Not to support solar geoengineering as a future climate policy option in international institutions

The open letter has now been signed by 585 academics from all parts of the globe and from across natural and social sciences, and it has been endorsed by more than 2,000 civil society organizations (4). Reasons include the severe, unknowable and unequally distributed risks of solar geoengineering; the implausibility of sustained, effective and inclusive global governance of such multi-decadal planetary interventions in a divided world; and the risk of distracting societies from ambitious greenhouse gas mitigation by keeping this speculative and risky option alive (5) —all concerns also emphasized in Siegert et al. (3).

Complimenting academic support, the 2025 AMCEN resolution marks the clearest political call yet for non-use, especially from governments most vulnerable to climate change. It builds on a 2023 AMCEN decision calling for a “global governance mechanism for non-use of solar radiation management” (6) and aligns with the African Group’s proactive leadership on this issue at the 6th UN Environment Assembly in 2024 (7).

This 2025 AMCEN decision not only reaffirms earlier rejection but also urges African countries to advance this unequivocal call for a non-use agreement in all relevant international negotiations and fora. It also calls for a UN General Assembly resolution to establish a solar geoengineering non-use agreement (1). This sends a clear message to the rest of the world: countries most vulnerable to climate change are leading the opposition to solar geoengineering. Proponents of research and investment in these technologies must acknowledge this political reality of strong African rejection.

Importantly, African countries are not alone. During the UNEA-6 meeting in 2024, the African Group’s stance was supported by several other countries in the Global South, including Colombia, Fiji, Mexico, Pakistan, and Vanuatu. In other UN settings, Vanuatu (8) and other Pacific Island nations (9) have urged states to “refrain from developing and using these technologies and prohibit their development and use” and to “proactively ban false and dangerous ‘solutions’ such as geoengineering”. Vanuatu’s Minister of Climate Change reiterated this call at the 2024 UN General Assembly Science Summit (10). Mexico, in 2023, became the first country to ban outdoor SAI-related experiments over its territory (11).

With AMCEN’s 2025 decision, close to sixty Global South countries have now spoken out against solar geoengineering and are calling for negotiation of a non-use agreement or equivalent mechanism. Concerns are also rising beyond the Global South. The European Union’s Scientific Advisory Mechanism, in its December 2024 opinion, urged a strongly precautionary stance, advising inter alia for an EU-wide moratorium on solar radiation modification, including large-scale experiments, and for pursuing a non-deployment regime internationally (12). In addition, civil society opposition remains strong, with over 2,000 organizations endorsing the academic non-use initiative, and African civil society also providing vocal support for AMCEN’s stance (13).

In short, the case is clear: solar geoengineering is a non-starter. This position is now being advanced unequivocally and convincingly by political leadership emanating from the Global South.

The way forward: governance and policy

A recent legal-governance analysis led by Dr. Dana Ruddigkeit of the German Environment Agency highlights the existing web of international obligations any deployment of solar geoengineering, particularly stratospheric aerosol injection, would confront (14). These include obligations concerning the atmosphere, biodiversity, the ozone layer, and human rights, all of which could be contravened by deployment. While fragmented, this legal web already provides a strong foundation for restrictive global governance of solar geoengineering (14). Hence, there is already a basis in international law for pursuing and institutionalizing non-use.

Political science research further outlines pathways toward restrictive global governance. A norm of non-use could emerge through joint declarations by like-minded states, non-binding UN resolutions, state-led “Schengen-style” clubs, or civil society-driven transnational approaches (15). Importantly, restrictive global governance of risky technologies is not unprecedented: prohibitory regimes already ban chemical and biological weapons, anti-personnel landmines, Antarctica mining, and human cloning, all deemed too dangerous or undesirable by the international community (16).

The intensifying scientific and political opposition to solar geoengineering sends a strong and clear message: The need of the hour is to ensure that the global response to climate change remains focused on the central task: securing a just transition away from fossil fuels to avoid further dangerous climate change — rather than pursuing speculative, high-risk planet-altering technological interventions that could exacerbate both climate impacts and global inequalities.

Copyright statement 

Copyright: © 2025 [author(s)]. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in Frontiers Policy Labs is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.     

Generative AI statement 

The author declares that no generative AI was used in the creation of this article.

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