Years of hard bargaining have failed to produce a policy architecture to adequately address the complexities of climate change. Very likely, such a structure will have to be sought though improvement of the partial architecture developed to date within the Framework Convention on Climate Change. We identify key architectural features that have emerged in the Convention process, and then explore extensions that will be necessary if the current approach is to serve for the long term. An important task is to break the deadlock over accession of developing countries. To this end we propose further incorporation in the negotiations of concepts of burden sharing according to ability to pay that already seem to be embedded in the Convention. The implications of alternative versions of such an approach are illustrated with a set of simple model simulations.