Cities, which are home to half of theworld’s population, are on the front lines of climatechange. Extreme temperatures, storms, and floods have ahigher impact in crowded urban areas. And cities in emergingeconomies will bear an even greater burden of climate changethreats. Given their vulnerability, as well as their abilityto affect change, cities will be key players in shapingefforts to lessen the impact of climate change. Now a numberof new initiatives are helping urban leaders better assessand respond to climate risks.