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

Greenhouse gas emissions abatement, negative emissions technologies, and adaptation are not, and most likely will not, be enough to prevent dangerous climate change and its deleterious impacts on humans, other species, and ecosystems. Some scientists and others are increasingly considering and researching solar geoengineering, which would reflect or block some of the sun's incoming solar radiation, as a potential complementary response. This introductory chapter offers an initial explanation of climate change and solar geoengineering, including its leading proposed techniques of stratospheric aerosol injection, marine cloud brightening, and cirrus cloud thinning. Solar geoengineering should be taken seriously, as its governance is both important and challenging. Among the major challenges is that solar geoengineering presents a high-stakes risk-risk tradeoff under conditions of great uncertainty. Another is that although earlier governance can be more effective, little is then known of such an emerging technology’s salient characteristics. The chapter outlines the topics covered by the remainder of the book and makes the author’s prior assumptions explicit.

Solar geoengineering is being considered and researched as a potential response to anthropogenic climate change. After exploring the causes and risks of climate change and other responses to it, this chapter describes solar geoengineering’s history and proposed methods, including stratospheric aerosol injection, marine cloud brightening, and cirrus cloud thinning. The current evidence regarding their potential capabilities, costs, and technical feasibility is presented. Evidence from models and natural analogs indicates that a moderate deployment of solar geoengineering would globally reduce climate change. It also appears to be technically feasible, rapid in its effects, inexpensive in its direct deployment costs, and reversible. Among solar geoengineering’s physical risks are imperfect compensation of climatic changes and consequent residual climatic anomalies, delayed recovery of stratospheric ozone, and irresolvable uncertainty. Social challenges include decision-making regarding deployment, problematic uni- or minilateral implementation, strained international relations, displacement of emissions abatement, biased future decision-making, and disagreement regarding ethics.