For centuries, cities have been centers of cultural innovation and commerce and the birthplace of some of humankind’s greatest ideas. But as resilient and powerful as cities are, they are also vulnerable to climate change. 

Worldwide, 70% of cities are already dealing with the effects of climate change and nearly all are at risk. 

Meanwhile, cities are also disproportionately responsible for carbon emissions — larger cities consume two-thirds of the world's energy and create over 70% of global carbon dioxide emissions. But cities also present an opportunity. Sustainable cities can have a lower carbon footprint per person through more efficient infrastructure and energy sources.  

With 10 years left to avoid the most catastrophic impacts of climate change, cities are more critical than ever in the fight against climate change — and it’s time that local leaders take action. City mayors are directly accountable to their constituents for their decisions, and are more nimble than state and national elected officials to take decisive action. What our cities do individually and in unison to address climate change can set the agenda for communities and governments everywhere.

Cities such as New York are beginning to stand up on climate stewardship by declaring a climate emergency and implementing strong emissions reforms plans — but we need more cities to follow their lead. We’ve identified Cape Town in South Africa and São Paulo and Manaus in Brazil as cities where mayors are close to taking steps to build a more sustainable city for their residents, but need the extra push to encourage them to make change. Email mayors around the world to take climate action now!