International Governance of Solar Geoengineering: Principles and Precedents.

Solar geoengineering (SGE) refers to a set of technological interventions which seek to counteract global warming by reflecting incoming solar radiation. SGE could produce significant benefits by reducing the average global temperature. However, it also poses serious and unpredictable risks at the regional and global level.

At present, there are no international agreements directly addressing SGE. My central research question asks what role principles of international environmental law (IEL) can play in filling this gap in the current legal architecture.

The existing literature typically concludes that the role of IEL principles in this area will be marginal. While these principles are widely accepted by states, they vary in their precise formulations, and there is uncertainty about their legal status. These limitations are said to be particularly problematic in relation to SGE, which poses risks of its own while seeking to address those created by climate change.

In this context, IEL principles urging precaution, harm prevention, or consideration of equity appear to cut both ways, undermining their ability to provide coherent action guidance. My project will reassess this dominant narrative, over the course of three complementary parts.

Part one will ask to what extent IEL principles can influence States' decisions on SGE deployment, independently of any new international agreement. I will employ doctrinal legal analysis of national and international court decisions to determine the legal status of the principles, as well as exploring avenues for their application and enforcement. This part will require engagement with conflicting methodological approaches for explaining how international law influences state behaviour.

Particular emphasis will be placed on the potential influence of the harm prevention principle, which has the most robust legal status and the most determinate and widely accepted content.

Part two will examine the frequently raised but underexplored suggestion that IEL principles could 'shape' future international agreements on SGE. I will ask what this might mean in practice, drawing on treaty texts, negotiating drafts, decisions of treaty bodies and academic commentaries to evaluate how IEL principles have influenced the formation and operation of existing agreements on issues analogous to SGE.

For example, I will examine how a precautionary approach to scientific uncertainty is operationalised through iterative decision-making under the Vienna Convention for Protection of the Ozone Layer, and through reversal of the burden of proof under the OSPAR Convention.

Part three will use IEL principles to evaluate specific proposals for governing various aspects of SGE, drawing on insights from part two. I will focus particularly on interdependencies and trade-offs between the satisfaction of different principles. For example, a system whereby States who deploy SGE are liable for damages caused could facilitate harm prevention by disincentivising reckless deployment.

However, it may simultaneously undermine equity if it requires States with less responsibility for climate change itself to compensate States with greater responsibility. My central objective is to use IEL principles, informed by their operational significance in other contexts, as a set of complementary normative lenses through which to view SGE governance proposals.

Using these lenses would enable us to identify problems and possibilities that are overlooked in the existing literature.

While this project is focused on future SGE deployment, it may also have more immediate legal and policy implications. Identifying complex trade-offs between IEL principles could call into question the likelihood of achieving legitimate and effective deployment governance. This would have implications for policies on research into SGE, and it would reinforce the need for urgent emissions reductions in order to avoid creating the need for tragic choices