Cities are at the heart of the fight against climate change. They are responsible for 80% of global GDP, 70% of GHG-emissions, and more than 75% of energy consumption. With an expected growth of the urban population to around 6.4 billion by 2050, these figures are on the rise. Urban material consumption, which already accounts for more than 60% of global material consumption, is projected to grow even faster than urban population itself. Large investments in urban infrastructure are needed to improve resource efficiency, reduce emissions and counteract other negative externalities of these trends.