This report provides an overview of existing and emerging GHG trading schemes, including those in Europe (EU ETS), North America (the WCI and RGGI), Australia, New Zealand, Japan (regional), China (regional) and South Korea. It discusses lessons learned across the systems and gives an outlook on the development of the future carbon market. The report illustrates that considerable diversity exists across cap-and-trade systems. Although unintentional, a potential benefit of this diversity is that it provides opportunities to compare different approaches and to facilitate transboundary learning. Individually, and in comparison, schemes may offer lessons that can be applied in the development or improvement of others. This report focuses on three large categories of lessons related to: the role of the political and economic process and context for establishing emissions trading systems; system design; and system implementation and oversight.