City governments are rapidly becoming society's problem solvers. As Sara Hughes shows, nowhere is this more evident than in New York City, Los Angeles, and Toronto, where the cities' governments are taking on the challenge of addressing climate change. Repowering Cities focuses on the specific issue of reducing urban greenhouse gas (GHG) emissions, and develops a new framework for distinguishing analytically and empirically the policy agendas city governments develop for reducing GHG emissions, the governing strategies they use to implement these agendas, and the direct and catalytic means by which they contribute to climate change mitigation. Hughes uses her framework to assess the successes and failures experienced in New York City, Los Angeles, and Toronto as those agenda-setting cities have addressed climate change. She then identifies strategies for moving from incremental to transformative change by pinpointing governing strategies able to mobilize the needed resources and actors, build participatory institutions, create capacity for climate-smart governance, and broaden coalitions for urban climate change policy.