This chapter discusses the societal and ethical challenges of climate engineering or large-scale intentional intervention in the climate system. Climate engineering is highly controversial, and raises many questions about the values of human societies and the desirability of technological visions of the future. Yet existing ethical theories and concepts may not be equipped to deal with the resulting ethical issues. To understand the potential social and political disruptiveness of climate engineering, we argue it must be placed in the context of global environmental changes caused by human activity. However, climate engineering is also accompanied by a high degree of uncertainty and risk in terms of potential and actual unintended impacts on natural processes and society. An important challenge stems from epistemic and normative uncertainties about the reversibility and variability in spatial and temporal scales of deployment. Epistemic uncertainties arise in the methodological framework of climate science, while normative uncertainties arise from the challenge of reconciling a plurality of values. A key question is how forms of climate engineering enforce or hinder disruption in social practices and institutional settings in the direction of a sustainable future. Climate engineering technologies can affect and potentially disrupt existing conceptions of climate and environmental justice, due to the scale and scope of impacts upon people currently living on the planet, future generations, and non-human species and ecosystems. The availability of climate engineering may also require rethinking the responsibility for climate mitigation, as well as applications of the precautionary principle. Climate engineering also raises the question of how the perspectives of affected communities can be adequately represented. While it remains unclear whether climate engineering techniques can genuinely assist in lessening the impacts of climate change, the question is whether and to what extent it should be used as a complementary approach to systemic changes in social, economic, and political practices.@en