We live in an urban age. Over half the world’s population now lives in urban areas, while the urban population is expected to reach 60% by 2030. At the same time, the importance of cities for national economic growth and climate change continues to increase. Three groups of cities will be particularly important for the global economy and climate: Emerging Cities, Global Megacities and Mature Cities. When combined, these 468 cities are projected to contribute over 60% of global GDP growth and over half of global energy-related emissions growth between 2012 and 2030 under business as usual.