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UNEA-6 Postmortem: Solar Radiation Modification


Lydia Dai, Thematic Facilitator for Disaster, Climate and Resilience, CYMG UNEP

Joshua Prentice, Thematic Facilitator for Environmental Law, CYMG UNEP/ International Policy Lead - SRM Youth Watch



Solar Radiation Modification (SRM) represents a deliberate intervention aimed at reducing the warming impact of anthropogenic climate change by reflecting sunlight back into space or facilitating the escape of thermal heat from the Earth. This strategy includes various approaches, with stratospheric aerosol injection (SAI) being the most researched, along with marine cloud brightening (MCB). While not a replacement for rampant and aggressive greenhouse gas emissions reductions, SRM could serve as a supplementary measure to temporarily limit climate change effects. The Intergovernmental Panel on Climate Change's (IPCC) Sixth Assessment Report notes that while SRM can partially counteract the warming effects of increased greenhouse gases, some intervention measures would also introduce significant regional and seasonal climate discrepancies due to the transboundary nature of SRM techniques.

At the Sixth Session of the United Nations Environment Assembly (UNEA-6) in Nairobi, Kenya, SRM resurfaced as one of the proposed nineteen draft resolutions, sponsored by Switzerland and initially co-sponsored by Monaco, Guinea, and Senegal— though the latter two withdrew their sponsorship in the weeks leading up to and during UNEA-6. This draft resolution marked Switzerland's second attempt to advance SRM discussions on a multilateral platform, following an unsuccessful attempt in 2019. Since then, significant advancements, including research activities and UNEP’s One Atmosphere Report, have deepened the understanding of SRM's potential impacts and governance issues.

The proposed draft resolution underscored the urgency of the climate crisis and raised concerns over the adverse effects of SRM, as well as the current lack of comprehensive multilateral oversight. It highlighted the challenges some countries, particularly those in the developing world, face in accessing science-based information on SRM technologies. Echoing the Precautionary Principle from the 1992 Rio Declaration, the resolution called for the establishment of a scientific assessment group under UNEP. This body would have been tasked with evaluating the current state of SRM and its research, assessing the potential impacts, risks, benefits, and uncertainties of these technologies, and addressing ethical considerations. The findings would inform further work, guide ongoing discussions under UNEA and support a more structured and informed international dialogue on SRM.

What happened at UNEA

Need for information vs. non-use  

Discussions at UNEA-6 revealed a complex dialogue between advocates of an SRM Non-Use Agreement and arguments for the necessity for more information. Initially, the African Group of Negotiators (AGN) declared their collective stance in favour of a non-use agreement. Senegal’s withdrawal as a Co-Sponsor of the resolution also reflected the country’s alignment with the stance adopted at the African Ministerial Conference on the Environment in 2023, which endorsed a non-use policy.

Despite these positions, there was an overarching acknowledgement of the necessity for enhanced scientific data and analysis concerning SRM, which is the resolution's core intention. However, concerns about the potential consequences and the resolution's specific recommendations for action remained. In response, the AGN proposed that UNEP conduct a survey to gather the positions of Member States on SRM research, and to consolidate these positions into a report. There were concerns about this addition by some Member States - mainly in developing countries - due to concerns about knowledge gaps that might influence the survey outcomes.

Amidst these discussions, Major Groups, particularly the Non-Governmental Organizations, Women, and Science and Technology Major Groups, strongly advocated for a non-use agreement. CYMG emerged as a singular voice emphasizing the critical role of scientific insight in shaping informed multilateral governance decisions, including those related to a potential non-use policy. CYMG advocated for the establishment of a transdisciplinary scientific expert group under UNEP to thoroughly evaluate the impacts of SRM, with the precautionary principle playing a key role in shaping scientific research. We also called for the inclusion of a diverse array of stakeholders, such as researchers from the Global South, indigenous populations, vulnerable groups, and youth, to ensure a comprehensive and inclusive evaluation process. The Constituency’s stance, while welcoming a non-use agreement on deployment, underscored the need for informed scientific evidence to feed into global governance processes. 

Debate between UNEP vs. other multilateral fora 

While recognizing the importance of gathering more information, a significant debate emerged over whether the UNEP was the appropriate body to lead discussions on this issue, given the potential overlap with activities in other multilateral forums.

The United States firmly opposed the creation of an expert group within UNEP and suggested that entities such as the World Climate Research Programme (WCRP) were more equipped to provide the necessary scientific insights on SRM. The US highlighted WCRP's Lighthouse Activity on climate intervention, stressing the need for coordination and reliance on WCRP's expertise. This position was supported by Japan, Canada, China, and later Saudi Arabia. Yet other Member States were hesitant to support this view.

For instance, the conversation also touched on the roles of the IPCC and the UNFCCC. India advocated for integrating SRM discussions within the UNFCCC, while the European Union and Australia emphasized the need to respect the mandates of existing multilateral environmental agreements. As SRM techniques have implications for climate, oceans and even ozone, all of which are governed by different treaty secretariats 

As discussions progressed, the debate moved to the method of conducting SRM assessments and whether UNEP was the right forum for such discussions. Proponents of WCRP argued for its strong scientific foundation and warned against rushed assessments that could mislead policymakers. They highlighted WCRP's comprehensive approach and its crucial role in supporting climate modelling efforts, suggesting that SRM's technical evaluation required a scientifically rigorous approach beyond UNEP's purview.

On the other hand, supporters of UNEP argued for a broad, interdisciplinary assessment encompassing physical, social, and environmental sciences, positing that UNEP was uniquely positioned to oversee such a comprehensive evaluation. They raised concerns about WCRP's focus on the physical sciences to the exclusion of other important disciplines and its lack of inclusivity regarding critical stakeholders.

Scope of the assessment and inclusivity of the assessment process

When the debate extended to the desired scope of the assessment, the United States and Saudi Arabia again expressed strong opposition to forming an expert group under the UNEA for SRM, and emphasised the need for further scientific foundation before proceeding with such discussions. Their stance highlighted a preference for deferring detailed policy and governance talks under UNEP until more scientific data were available and underscored the value they place on the work of the WCRP and its contribution to science-driven policy. 

On this point, Switzerland clarified that the intention behind this resolution was to allow a more comprehensive evaluation encompassing a wide array of physical and non-physical sciences. The European Union and Brazil also argued for the inclusion of social sciences, and Colombia emphasized the need to address human rights issues. The EU particularly criticized the WCRP's focus on climate modeling as too narrow and advocated for a more comprehensive and inclusive discussion that also encompasses policy implications, and suggested that research should primarily consider risks over potential benefits.

Discussions on the naming and structuring of the proposed group also revealed diverse preferences among countries. Suggestions ranged from expert, open-ended, scientific, ad hoc, and intergovernmental, to consultative. A key point of contention was who should lead the report's drafting process, with Switzerland proposing UNEP's initial authorship, subject to expert group review, while the EU and the African Group favoured entrusting this responsibility to an intergovernmental group, which would allow member states a greater degree of control over the output.

In the concluding hours, there was an emerging proposal around establishing a "repository" of SRM information managed by UNEP, with the intention of finding a negotiated outcome. However, opinions still varied wildly on the contents of as well as the sources of input to the repository: the African Group envisioned it being a collection of country submissions on their SRM positions; the EU sought a broader scope, including transdisciplinary perspectives and indigenous views; the US suggested it serve as a database for voluntary research disclosures.


As the assembly neared its conclusion, unresolved disagreements and increasing tensions between countries became more pronounced. This heightened polarization significantly hindered any possibility of reaching a consensus. Key issues that intensified the divide included the Convention on Biological Diversity's (CBD) "de facto moratorium" on certain biotechnologies and the call for a non-use agreement on SRM. Fiji and Pakistan notably referenced these points and effectively stalled the discussions by rejecting any consideration of the proposed new text.

In the face of these obstacles and the lack of a clear path forward, Switzerland decided to withdraw the draft resolution during the final plenary session. This move underscored the complexities and challenges still inherent in multilateral conversations on SRM. 

Looking ahead

The outcome was not dissimilar from what happened at UNEA-4. This now leaves the knowledge gap unbridged, especially within the Global South. As research into Solar Radiation Modification techniques ramps up, there is a greater urgency to govern the science and potential deployment of these technologies. 

Given discussions about UNEP’s mandate to even administer this resolution, we may see SRM rear its head again within UNFCCC and Montreal Ozone Protocol conferences. 

Moving forward, CYMG, in collaboration with SRM Youth Watch and other interested and relevant youth-led initiatives, will engage with researchers, policymakers, Member states and advocates to ensure an inclusive and boundary-expanding space for the governance and development of climate and other forms of geoengineering.

Note: The views and opinions expressed in this document are solely those of the authors and may not necessarily reflect the official policy or position of their respective employers or any other affiliated organizations. The content provided is for informational purposes only and has been prepared from the authors' own research and personal experiences as of the date of publication.

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