As the global population increases in a climate-stressed world, we face mounting challenges. On the one hand, cities consume close to 65% of the world’s energy and generate more than 70% of global greenhouse gas emissions. But on the other, they drive economic growth and account for 80% of global GDP. They are home to over half of the world’s population. Over the next 25 years, the number of people living in cities will rise to 6 billion, adding 2 billion more residents to already crowded spaces.