Around the world, policymakers are facing the challenge of finding the most efficient systems to limit global warming pollution. Nations, states, provinces and cities are increasingly using efficient, market-based emissions trading programs as a way to cut carbon, forming a world of “bottom-up” climate actions. In fact, 10 percent of the world’s population and a third of its GDP now come from areas implementing carbon caps. Environmental Defense Fund has partnered with the International Emissions Trading Association (IETA) to create The World's Carbon Markets: A case study guide to emissions trading.