Chapter 5 addresses the potential use of climate engineering technologies as a way of counteracting anthropogenic global warming. These technologies encompass methods for the permanent removal of atmospheric carbon dioxide, for instance via its direct capture from ambient air and subsequent geological storage. They also include more controversial technologies that would modify the planetary albedo in order to reflect a small fraction of incoming sunlight back into space in order to induce an artificial cooling effect. These two sets of technologies play out against the background of the increasingly dim prospects of achieving international temperature targets in line with the 2015 Paris Agreement. The chapter traces institutional responses to both negative emissions technologies and solar geoengineering across a multitude of international forums, including the Convention on Biological Diversity, the London Convention on the Dumping of Waste at Sea, and the Paris Agreement itself.