Negotiations pursuant to the Durban Platform for Enhanced Action appear likely to lead to a 2015 Paris agreement that embodies a hybrid climate policy architecture, combining top-down elements, such as for monitoring, reporting, and verification, with bottom-up elements, including “nationally determined contributions” from each participating country, detailing what it intends to do to reduce emissions, based on its national circumstances. For such a system to be cost-effective—and thus more likely to achieve significant global emissions reductions—a key feature will be linkages among regional, national, and sub-national climate policies. By linkage, we mean a formal recognition by a greenhouse gas mitigation program in one jurisdiction (a regional, national, or sub-national government) of emission reductions undertaken in another jurisdiction for purposes of complying with the first jurisdiction’s mitigation program. We examine how a future international policy architecture could help facilitate the growth and operation of a robust system of international linkages of regional, national, and sub-national policies. Several design elements merit serious consideration for inclusion in the Paris agreement, either directly or by establishing a process for subsequent international elaboration. At the same time, including detailed linkage rules in the core agreement is not desirable because this could make it difficult for rules to evolve in light of experience.