Open Access

Urban areas cause over 70% of direct and indirect CO2-emissions worldwide. To achieve the internationally agreed goal of limiting the global temperature increase to 1.5 to 2 ° C, considerable efforts to reduce emissions in cities are required. Mobilizing significant greenhouse gas reductions in cities is, however, a major challenge due to their very heterogeneous structures and a large number of small and varied emission sources (e.g. traffic, buildings). In addition, the organisational structures of urban emission sources are much more diverse than those of e.g. major industrial point sources. A general challenge for responsible decision-makers and institutions is that they have limited access to investment capital to implement large-scale measures to reduce greenhouse gas emissions. Carbon market mechanisms under Article 6 of the Paris Agreement can offer new opportunities for the mobilisation of large-scale emission reduction measures and policies. This research project first examined the prevalence and experience of urban reduction projects within the framework of the Clean Development Mechanism (CDM), Nationally Appropriate Mitigation Actions (NAMAs) and Transformative Actions Programs (TAP). Building on this, various conceptual approaches to the implementation of Art. 6 in cities were developed. In order to take appropriate account of the different national structures and framework conditions, a “menu approach” with uniform principles and standards is proposed. In addition, the study examines approaches to determine the additionality of urban mitigation activities and discusses various financing options.