This paper reviews problems connected to the use of the deep-sea and sub-sea geological formations for carbon sequestration. We will focus on the risks and dangers involved in using this kind of large-scale engineering approach, which is not yet fully tested, to combat global warming. We will not provide a complete discussion on the technologies involved, but concentrate on a few principal questions, such as the responsibility of environmental scientists involved in this research. We will also discuss carbon sequestration in relation to the precautionary approach. We argue that there may be a place for large-scale engineering attempts, but this should be the last rather than the first option.