'With the international community now galvanized to put the world on a climate safe pathway, the evidence is stacking up that cities have a key role to play. The second edition of the ARC3 report from the Urban Climate Change Research Network provides a critical knowledge base for global cities as they respond to climate change challenges and seize the economic opportunities of low carbon, climate resilient development. Leading mayors, through networks such as the C40, are learning from each other, exchanging ideas and thereby accelerating local action on the ground.' Mark Watts, Executive Director, C40 Cities Climate Leadership Group