Although states and international organizations regularly rely on scenario modelling to plan for the future, it is not generally used in legal analysis. This article explores, in a preliminary fashion, whether (and if so how) the use of scenarios can illuminate such analyses. Five high-level scenarios concerning the future of international climate change law are developed, ranging from an optimistic scenario, in which there is coordinated mitigation between states within the confines of the United Nations Framework Convention on Climate Change, to a pessimistic scenario, in which each state engages in its own autonomous adaptation to climate change. Some consequences for individual states of each scenario are then explored and some possible legal responses of states are developed. Governments should work together in mitigation and adaptation to achieve a global response to climate change, and should work to secure advantages in the carbon markets for their own companies, develop a geoengineering strategy, and be aware that recasting climate change as a security issue risks undermining the logic of global cooperation.