Emission limitation commitments will form a central element of any future architecture of the climate regime. Increased mitigation efforts from virtually all countries will be required in designing an adequate and equitable global climate agreement, i.e. deep emissions cuts in industrialized countries and the avoidance/reduction of emissions in developing countries. Most of the research about the design of a post-2012 climate regime deals with the involvement of developing countries into a future limitation regime. This project focuses on future mitigation commitments for Annex I countries. Options for differentiation among Annex I countries will be evaluated on the basis of an open, transparent and analytically-based framework. The project has two main elements namely to (1.) take stock on current mid- and long-term climate targets in Annex I countries beyond the first commitment period; (2.) (re-)group industrialised countries with similar national circumstances as a basis for assigning differentiated mitigation obligations in future commitment periods. The aim is to identify groups of Annex I countries each including countries with similar national circumstances that can take on specific levels/types of mitigation and financial commitments. The results of the project are published as a Wuppertal Paper no. 155.