The mayors of 94 megacities, from Paris to Mexico City, also just declared that the planet is in a state of climate emergency.

The world’s most polluting countries aren’t acting quickly enough to cut emissions, and at the recent UN Climate Summit, the two largest polluters—China and the U.S.—didn’t make any new promises to tackle climate change. But cities around the globe are moving faster. Now, a group of mayors of megacities, from Paris to Mexico City, is stepping into the void of leadership and calling for a Global Green New Deal.

“It’s necessary because we’re in a climate emergency,” says David Miller, the former mayor of Toronto, who now serves as the regional director for North America for the C40 Cities network, a coalition of 94 megacities focused on driving urban action on climate solutions. At a meeting today in Copenhagen, the mayors announced that they recognize that global climate emergency. They also endorsed a new commitment to reach peak emissions by next year, cut global emissions in half by 2030, and be carbon neutral by 2050. It’s the speed of progress necessary to keep the world from heating up more than 1.5 degrees Celsius, a critical goal to prevent the worst impacts of climate change.