We’ve been mayors of New York, Paris and Rio. We know climate action starts with cities

The Paris Climate Agreement, already signed by more than 175 countries, was successful in large part because national governments recognized cities’ progress in reducing carbon emissions. On Thursday, as world leaders gather in Washington DC to discuss how to reach the goals set in Paris, they should focus on helping cities do even more, and act faster, to reduce those emissions. Cities account for most of the world’s carbon emissions, and their share will continue…