This document discusses megacities and climate change. It outlines that the C40 Cities Climate Leadership Group represents 67 megacities that are home to 8% of the world's population and generate 21% of global GDP, but also produce 5% of global greenhouse gas emissions. The C40 convenes networks for peer-to-peer exchange and works to address financing challenges faced by cities, such as turning ideas into projects, understanding investor needs, and issues of creditworthiness that impact scaling up of climate solutions. Activities to help improve city creditworthiness include a new financing network, creditworthiness academy with the World Bank, city challenges analysis and action plans, and a mayoral-level pledge.