This paper is intended to explore the possibilities for a more consistent approach in the WTO to subsidies as a policy tool, in the context of one particularly important domestic and global policy challenge: climate change. The paper begins by outlining the possible role that that subsidies might play in climate mitigation policy. Then it explains and examines existing WTO rules on subsidies; these rules, the analysis shows, create legal uncertainty with respect to a range of possible subsidies policies associated with climate mitigation schemes.