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. Over 90% of all urban areas are coastal, putting most cities on Earth at risk of flooding from rising sea levels and powerful storms.

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 emissions. But cities also present an opportunity. Sustainable cities can have a lower carbon footprint per person through more efficient infrastructure, planning, energy sources, and providing green jobs for residents. 

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. 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 (South Africa), Bristol (UK), Helsinki (Finland) and São Paulo (Brazil) as four cities where city 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. 

Tweet at mayors around the world to take climate action now!