Climate treaties have adopted national targets and timetables for emissions reductions, and economists have advocated using emissions trading and carbon taxes to achieve these. After three decades of trying this approach, little has been achieved, largely due to the failure to overcome free riding incentives. I propose a completely different approach that rests on four pillars. First, a focus on sectors rather than economy-wide measures. Second, a focus on technology-switching rather than emission reductions. Third, a focus on global transformation rather than national action. Finally, use of trade linkages to achieve critical mass. Important to my analysis is the observation that technology switching is both stymied by “lock-in” and propelled by increasing returns. Lock-in makes it difficult to achieve even small reductions in emissions, whereas increasing returns makes it easy to achieve very substantial reductions in emissions, once critical mass has been achieved. The role of treaties is to target technologies for switching, and to use trade measures to achieve critical mass rather than to correct for “leakage.”