If we are to effectively combat climate change, cities have to make bold moves that will shape the future. Take Burlington, Vermont and San Francisco, California for example. Burlington began its transition to a net-zero economy back in 1978 when it replaced its coal plant with a power station fueled by biomass, and has added wind, solar, and hydropower to become the first US city to source all of its electricity from renewables. San Francisco isn’t quite there yet, but has showed other big cities how to approach 100 percent renewable by mandating all newly constructed buildings to have solar roofs.