May 2013 - This special issue of Carbon Mechanisms Review is published on the occasion of the Carbon Expo 2013 Trade Fair in Barcelona. It contains a comprehensive analysis of the status of the global carbon markets. The article reflects the experiences with the project-based mechanisms CDM and JI, including an analysis of the criticisms. On this basis, lessons learnt and the challenges for the immediate future are laid out. A synopsis of the recent submissions for the New Market Mechanisms and Framework for Various Approaches negotiation stream completes the issue.