Sunlight reflection methods (SRM) – also known as solar geoengineering – would affect the whole world. Answering the social, political, and economic questions SRM raises could be even more challenging than navigating its physical impacts. As climate risks continue to grow and increasing attention is paid to SRM, discussions about the rules and policy frameworks that may be needed are also growing.
The expanding SRM landscape
As the world continues to warm, increasing attention is being paid to sunlight reflection methods (SRM), or solar geoengineering. This attention has taken the form of more research and discussion, as well as increased funding and a growing number of outdoor experiments.
Scientific assessment and research funding will play a crucial supporting role in the governance of SRM. The leading scientific academies of several countries, including the Royal Society in the UK, as well as international bodies such as the United Nations Environment Programme, have conducted assessments of SRM, drawing on the research conducted in the field.
SRM research has been mostly funded by governments, mainly in the Global North, and philanthropies, mainly in the US. The latter have been the largest source of funding for research in the Global South, much of which is distributed through the Degrees Initiative. There is still relatively limited participation in the Global South, raising questions of justice given those countries’ high degree of vulnerability to climate change and, potentially, climate interventions.
In addition, Stardust Solutions, a for-profit company, recently entered the field. It has raised tens of millions of dollars in funding and has generated significant criticism among experts.
Given the growing interest and activity, questions of how to govern SRM are looming larger. From the current focus on computer modelling research through outdoor experiments and eventually potential deployment, what is being done to guide and govern SRM, and what form might that take in the future?
International law and SRM
There is currently no comprehensive international governance framework for SRM, though there is a patchwork of agreements and organisations that address related issues.
SRM is not banned outright under international law. However, the 1977 ENMOD treaty prohibits the hostile use of environmental modification without restricting peaceful uses. The Convention on Biological Diversity has also passed decisions urging countries to avoid potentially harmful deployments of SRM, but these are not legally binding.
There are also relevant legal obligations from what is known as customary international law, such as the “no-harm rule”, which requires countries to take steps to reduce significant environmental harms to other countries. While customary international law could present legal obstacles to SRM, it does not amount to an outright prohibition.
While no comprehensive rules on SRM have been set at the international level, there is increasing engagement with the issue in intergovernmental organisations as well as regional bodies.
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How should outdoor experiments be governed?
In the absence of top-down, international governance, researchers and their funders have developed their own approaches to SRM research governance. Most SRM research, like computer modelling or public perception studies, is conducted without intervening in the environment; outdoor experiments have proved more controversial, with some cancelled after vocal opposition.
Academic efforts to identify a responsible governance approach for outdoor experiments have arrived at a broadly similar set of principles, with key points including:
- Managing risk and uncertainty – through risk assessments, efforts to minimise risks, monitoring, and measures to respond to any potential damages.
- Promoting research integrity – through transparency, peer review of research, open publication of findings, and limiting the impact of commercial interests.
- Ensuring public engagement – through outreach and engagement with the public, including vulnerable and Indigenous groups.
Putting these governance principles into practice would raise several challenges. For example, what would be considered sufficient public engagement? There are also definitional issues: what counts as an outdoor SRM experiment, and how are they distinguished from other outdoor atmospheric experiments?
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Near-term governance options
Near-term governance options could take many forms at a variety of levels, from regional and national frameworks to initiatives set up through civil society organisations, philanthropies, or the private sector.
A parliamentary research briefing from the UK noted possible options for improving SRM governance, including more international dialogue on SRM, improved oversight of some SRM activities, greater clarity on what counts as “SRM research” at different scales, and expanded public engagement.
Governance can help guide the field, setting priorities and moving research forward, though some prefer a more restrictive approach.
Hundreds of academics and many civil society groups have signed up to the “solar geoengineering non-use agreement” campaign, which goes further than just calling for SRM not to be deployed. It also calls for no outdoor experiments, no public funding, no patents, and no normalisation of SRM in international institutions.
Some African ministers have indicated support for a non-use agreement but not for the broader restrictions called for by the non-use campaign. Several US states have passed laws banning solar geoengineering, cloud seeding, and other atmospheric modifications in recent years. European leaders have also called for a moratorium, or temporary prohibition, on SRM deployment, while still allowing small-scale outdoor experiments under certain conditions.
Long-term governance challenges
As the impacts of climate change worsen over the coming years and decades, the incentives for a country or coalition of countries to develop and potentially deploy SRM will grow. Given the technical feasibility of stratospheric aerosol injection (SAI), it could in theory be deployed as early as the 2030s.
This raises important governance questions now, before any such deployment begins:
- How would the risks of an SRM deployment be weighed against the risks of not deploying as climate change continues to worsen?
- How specifically would decisions about a deployment be made? Which institutions, governing bodies, and multilateral processes would be involved?
- How might equity and justice be factored into decisions around SRM, given the wide variation in vulnerability to climate change as well as the potential negative impacts of a deployment?
Were a decision to deploy made, the deployment itself would pose significant political and governance challenges, and there are many open questions:
- Could this lead to conflict between countries? What steps could be taken to build trust and develop cooperative approaches to decision-making on SRM?
- What would this mean for other efforts to address climate change? Could this undermine efforts to cut emissions or support adaptation to climate risks?
- How could SRM affect weather extremes? How might claims of harm from SRM be adjudicated and resolved?
- What if it failed? What could be done to maintain the long-term stability of SRM deployment and reduce the risk of termination shock?
Steps are already being taken today by a range of actors in many countries, shaping how this field develops. Good governance of SRM will depend on understanding the issues, tracking developments in the field, and considering a diverse range of perspectives on this challenging emerging issue.
