This book analyzes major ethical issues surrounding the use of climate engineering, particularly solar radiation management (SRM) techniques, which have the potential to reduce some risks of anthropogenic climate change but also carry their own risks of harm and injustice. The book argues that we should approach the ethics of climate engineering via "non-ideal theory," which investigates what justice requires given the fact that many parties have failed to comply with their duty to mitigate greenhouse gas emissions. Specifically, it argues that climate justice should be approached comparatively, evaluating the relative justice or injustice of feasible policies under conditions that are likely to hold within relevant timeframes. Likely near-future conditions include "pessimistic scenarios," in which no available option avoids serious ethical problems. The book contends that certain uses of SRM can be ethically defensible in some pessimistic scenarios. This is the first book devoted to the many ethical issues surrounding climate engineering.