Reckless or righteous? : reviewing the sociotechnical benefits and risks of climate change geoengineering

Geoengineering options such as negative emissions technologies (NETs) or greenhouse gas removal (GGR) may need to contribute towards decarbonization, by removing CO2 from the atmosphere and storing it safely in biological or geological sinks, or reflecting sunlight back into space via solar radiation management (SRM). Despite concerns about them, GGR and SRM are increasingly discussed as crucial complements to traditional climate change mitigation. Others routinely dismiss both SRM and GGR methods as a distraction from mitigation, or even as a potential moral hazard that induces complacency in reducing emissions. Yet, if climate impacts turn out to be more sudden and severe than currently known, such strategies could provide a rapid backstop to implement deeper emissions reductions, especially with techniques that require time to scale-up. Despite their importance and controversial status, most research on GGR and SRM remains technical, rather than social, and that knowledge of their technical characteristics remains limited, even within the physical and engineering sciences. Moreover, existing GGR and SRM options are changing rapidly in terms of their technical design, cost, and performance, and therefore scalability and deployment potential. To contribute to the debate, this study reviews and summarizes a large number of geoengineering assessments published over the past decade to document prospective benefits, but also reveal potential risks. It aims to provide a comprehensive evidence base on GGR and SRM technologies that is rigorous, timely, and interdisciplinary. This article begins by briefly defining geoengineering and associated technologies, describing how various techniques work, and summarizing recent market trends up until early 2021. Then, it discusses a series of advantages and disadvantages to these options before identifying tensions, research gaps, and a critical research agenda. It concludes with implications for research, policy, and governance.