Abstract

Continued failure to limit emissions of carbon dioxide and other greenhouse gases that are causing global climate change has brought increased attention to climate engineering technologies, which actively modify the global environment to counteract heating and climate disruptions caused by elevated greenhouse gases. Some proposed forms of CE, particularly spraying reflective particles in the upper atmosphere to reduce incoming sunlight, can cool the average temperature of the Earth rapidly and cheaply, thereby substantially reducing climate-related risks. Yet CE interventions provide only imperfect corrections for the climatic and other environmental effects of elevated greenhouse gases, and carry their own environmental risks. Moreover, they may also increase other risks, by weakening political support for essential emissions reductions or providing new triggers for international conflict. These technologies thus require international governance, but also pose novel and severe challenges to current international laws and institutions. Effective governance of CE will require a capacity to make decisions regarding the conditions, if any, under which specific interventions are authorized, plus realtime operational oversight of any interventions that are conducted. Decision processes must be effectively linked with scientific research and assessment, and with institutions to manage and respond to threats of CE-related conflict. We advance preliminary suggestions to address two priority areas for early investigation: how international cooperation on early CE research can help develop shared norms that can grow robust enough to support future decision needs; and how early research and development on CE can be made to complement and encourage, rather than undermine, parallel efforts to reduce climate risks by cutting emissions.