Mayor Mike Johnston is showing how cities are rethinking infrastructure to cut emissions.

Denver is piloting a new thermal energy network that uses water, geothermal energy (and even excess heat from wastewater) to heat and cool downtown buildings, replacing its aging, fossil fuel-powered system. By reusing existing infrastructure and tapping new energy sources, the city is decarbonizing buildings, which are its largest source of emissions.

As federal action stalls, climatemayors are advancing scalable solutions to power their cities.