Summary

The means to combat dangerous anthropogenic climate change constitutes a portfolio. Beside abatement of greenhouse gas emissions, this portfolio entails adaptation to changing climate conditions, and so-called climate engineering measures. The overall portfolio has to be judged on technical, economic, and moral grounds. This requires an in-depth understanding of the moral aspects of climate engineering options. Climate engineering (CE) is a large-scale intentional intervention either in carbon cycles (carbon dioxide removal; CDR) or in solar radiation (solar radiation management; SRM). The ethical discourse on climate engineering has gained momentum since the 2010s. The set of arguments pro and contra specific CE technologies constitute a vast landscape of discourse. Single arguments must be analyzed with scrutiny according to their ethical background, their normative premises, their inferential logic, and their practical and political consequences. CE ethics, then, has a threefold task: (a) it must suppose a solid understanding of different CE technologies and their risks; (b) it has to analyze the moral arguments that speak in favor or against specific CE technologies; and (c) it has to assess the impacts of accepting or rejecting specific arguments for the overall climate portfolio’s design. The global climate portfolio differs from ordinary investment portfolios since stakes are huge, moral values in dispute, risks and uncertainties pervasive, and collective decision-making urgent. Any argument has implications of how to design the overall portfolio best. From an ethical perspective, however, one must reflect upon the premises and inferential structures of the arguments as such. Analysis of arguments and mapping them logically can be seen as core business of CE ethics. Highly general arguments about CE usually fall short, since the diverse features of individual technologies may not be addressed by overarching arguments that necessarily homogenize different technologies. It can be stated with confidence that the moral profiles of CDR and SRM are highly different. Every single deployment scheme ought to be judged specifically, for it is a huge difference to propose SRM as a substitute for abatement, or to embed it within a comprehensive climate portfolio including abatement and adaptation, where SRM will be used sporadically and only for a matter of decades.