Existing norms, rules, and institutions seem insufficient to govern solar geoengineering in the long term. This chapter recommends additional and feasible measures to help ensure that it is researched, developed, and – if appropriate – used in ways that improve human well-being, are sustainable, and are consistent with widely shared norms. This will be challenging for reasons such as political contestation, conflicting desires for early governance and the reduction of uncertainty, and the endeavor's speculative nature. The suggestions are divided into rough stages of indoor and small-scale outdoor research, large-scale outdoor research, and deployment. The suggested forms of governance are norms, standards, and best practices; cooperation among nonstate actors; institutionally affiliated committees; state law; international institutions, including one dedicated to solar geoengineering; and – most speculatively – a multilateral agreement. Among governance's functions are reducing uncertainty and environmental risks, synthesis and assessment of results, public engagement, and preventing premature implementation, international tensions, and harmful abatement displacement.

Because of its transboundary effects and because states will be the primary actors, large-scale solar geoengineering and its governance are matters of international law. This is the third of four chapters that consider international legal rules, here regarding human rights. The chapter introduces international human rights law and how it relates to the environment and climate change. It reviews and critiques the limited literature on human rights and solar geoengineering. The remainder considers the issues in four ways. First, solar geoengineering is presently being explored as scientific research, for which international human rights law has provisions for the researcher and the potential beneficiaries of resulting knowledge. Second, outdoor research may affect people as research subjects, for whom international human rights law provides some protections. Third, procedural human rights to information, participation in public affairs, and legal remedies are widely recognized. Finally, the international law of substantive human rights such as those to health, to an adequate standard of living, to be free from hunger, and to life could inform solar geoengineering governance.

This chapter considers the research, development, and implementation of solar geoengineering by nonstate actors and their governance by intellectual property policies. Although some observers are concerned that nonstate actors could deploy it, states will probably retain control over operational decision-making regarding large-scale outdoor tests and implementation. At the same time, commercial entities will play roles – most likely as contractors in public procurement – as providers and innovators of goods and services for solar geoengineering activities. A leading means through which states govern nonstate actors in innovative domains is policies for intellectual property, particularly patents. This chapter reviews the current landscape of patents related to solar geoengineering and the social challenges that such intellectual property could pose. It comments on others’ proposals for intellectual property policies specific to solar geoengineering and also recommends one. Importantly, the suggested "research commons," which is centered on a system of patent pledges, does not require state action and could arise bottom-up among researchers and other nonstate actors.

The most widespread – and arguably influential – concern regarding solar geoengineering has been that it would harmfully displace emissions abatement. Notably, there was a similar objection to adaptation, although one no longer hears it. Moral hazard and risk compensation offer imperfect analogies, and the empirical evidence for their magnitudes is mixed. Public opinion studies that ask people how they would respond to solar geoengineering consistently do not imply abatement displacement and often point toward the reverse, in which solar geoengineering increases support for abatement. The chapter identifies four genuine hazards regarding the relationships among the responses to climate change. Notably, all four are challenges to governance in general and are not limited to climate change policy. These imply some, albeit limited, policy options to reduce abatement displacement. Linkages between international abatement and solar geoengineering policies have some potential. I suggest that the abatement displacement concern is widespread for reasons largely unrelated to reducing climate change and its negative impacts, but instead is grounded in political coalitions and worldviews

Solar geoengineering is presently being researched through indoor work and outdoor experiments without potential transboundary impacts. Existing national and subnational legislation and common law govern such activities, including for their environmental risks, and is an essential component of the existing governance framework within which solar geoengineering is developing. To offer a case study, this chapter reviews applicable American law. The United States was chosen because its environmental legal regime is among the most elaborate and influential, and because solar geoengineering research is presently moving forward most rapidly there. The text considers three major pieces of federal environmental legislation: the Clean Air Act, the National Environmental Policy Act, and the Endangered Species Act. Liability for harm, which is found in the common law of torts, is briefly introduced. Thereafter, the chapter describes relevant laws regarding weather modification and marine pollution, as well as a federal geoengineering bill. A salient question throughout this concerns the extraterritorial application of US law.