Governance of solar radiation modification research

DOI: https://doi.org/10.58248/PN773

By 2025 the Earth had warmed by 1.4°C relative to pre-industrial levels, while current emissions pathways point to around 2°C warming by 2050. This has prompted increasing interest in research on technologies typically intended to reflect sunlight away from the Earth to reduce warming globally or regionally. This technology is called solar radiation modification, sometimes referred to as ‘solar geoengineering’.

Research suggests that, deployed as a complement to other climate policies, some forms of solar radiation modification might reduce climate risk globally, though it may increase risks regionally. This has led to growing socio-political concerns, including the risks of conflicts over unilateral deployment and the difficulty of developing global governance arrangements. Some are also concerned that deploying such technology could undermine efforts to reduce greenhouse gas emissions.

Contributors to this POSTnote said that solar radiation modification could never function as a stand-alone solution to climate change. However, there is increasing interest in technology development and outdoor field experiments. From 2007 to 2025, global funding for solar radiation modification research totaled around $340 million, around $170 million of which came from public sources. In 2025 alone, over $60 million of funding came from commercial or philanthropic sources.

Contributors expressed concern over the lack of a dedicated, binding international framework governing solar radiation modification research. However, existing regulations and governance processes could apply to specific activities, locations, substances or impacts.

The UK Government is not in favour of deploying solar radiation modification and has no plans to do so. It supports responsible research that advances scientific understanding of the risks and impacts associated with solar radiation modification and complies with all domestic and international regulations.

How is solar radiation modification research conducted?

Research is mostly but not exclusively focused on stratospheric aerosol injection. This would involve spraying aerosol particles or their precursor gases into the stratosphere to reflect sunlight into space, similar to the cooling effects of volcanic eruptions. This is considered to be cheaper, technically easier and better understood than other techniques.

Most research involves computer modelling of climate responses to solar radiation modification. These models can be improved by using observational and/or experimental data, including from laboratory studies, monitoring of natural analogues (for example, volcanoes), and in some cases, carefully governed outdoor studies.

Small-scale outdoor experiments can involve releasing material into the atmosphere, at ranges from one kilogram to one ton of material and vary with respect to the equipment used and intended effects (or they may involve no material release). Intermediate-scale releases could involve up to 1,000 tonnes of material.

The UK funds indoor and outdoor research through the Exploring Climate Cooling programme, run by ARIA (a government-sponsored funding body). The ARIA funding package will support five small-scale outdoor experiments. It also funds modelling research through the Modelling environmental responses programme, run by the National Environment Research Council.

Outdoor research involves new or elevated risks; consequently, public and research communities raise more concerns about outdoor research experiments than other research.

What are the difficulties in formalising solar radiation modification research governance? Geopolitics

Generally, funding for research and development has been concentrated in wealthier countries; for example, the UK’s ARIA funds research projects across the world. Wider involvement in solar radiation modification research and governance is growing but remains limited.

This raises ethical concerns, given the possibility that wealthier countries may fund research that damages the environment in less wealthy countries. Some contributors raised concerns about not repeating historical ethical failings in international research. Other geopolitical considerations include:

• Differing views of solar radiation modification research among major powers; for example, as either a national security concern or a disruptive tool
• Perceived cross-border impacts of outdoor research activity
• Lack of transparency about activities by state or non-state actors
• Adapting existing international climate monitoring systems, for example the European Organisation for the Exploitation of Meteorological Satellites

Ethics and legislation

An ongoing concern over solar radiation modification research is whether it could weaken national emission reduction efforts (known as ‘moral hazard’ or ‘mitigation deterrence’). Some contributors stated that such concerns have delayed implementation of research governance. Others cited the lack of an international institution capable of enforcing governance as a major impediment to this research.

Other ethical research considerations raised include:

• how climate policy decisions may affect future generations
• how to include representative voices from around the world in research decisions
• how to obtain free, prior and informed consent from affected communities
• whether investing in researching solar radiation modification could ‘lock in’ a technological development path towards deployment, at the expense of alternative technologies

Relevant UK legislation includes the 2016 Environmental Permitting Regulations (England and Wales), 2018 Environmental Authorisations (Scotland), and 2003 Pollution Prevention and Control Regulations (Northern Ireland).

The Horizon Europe/UK Research & Innovation funded Co-CREATE project is exploring how domestic and international legislation may be adapted or crafted for governance of solar radiation modification research.

The Nuffield Council on Bioethics is conducting research into the ethical considerations of solar radiation modification research, with the aim of developing recommendations for research and development, including its governance, in the UK.

What has been tried already?

Some outdoor research projects with self-authored codes of conduct or governance principles have gone ahead, but others have been cancelled because of public opposition or conflicts of interest. ARIA’s outdoor projects have been planned under its own internal governance arrangements.

The international Solar Geoengineering Research Governance platform is a forthcoming voluntary effort to encourage responsible solar radiation modification research by providing practical governance tools.

Some contributors stated that effective solar radiation modification research governance will require impact assessment, institutional capacity, inclusive stakeholder participation, and adaptive governance mechanisms, in addition to regulatory oversight.

Acknowledgements

This briefing was produced in consultation with experts and stakeholders, who are listed at the end of the briefing. The briefing was co-funded by UK Research & Innovation. POST would like to thank everyone who contributed their expertise to this briefing.