Carrying on: In Chicago yesterday, former President Barack Obama called cities “the new face of American leadership on climate change,” commending the charter that 45 mayors signed to cut greenhouse gas emissions by 2025. As President Trump plans to withdraw the U.S. from the landmark Paris Agreement, the mayors’ pact continues local commitments to the international climate accord. USA Today reports:

"In this environment right now, it’s easy sometimes to feel discouraged, and feel as if people are talking past each other,” said Obama, who did not mention President Trump by name in his 14-minute address to the summit. “This is where the particular talents of mayors come in. Because first of all, you are used to dealing with folks who can sometimes be unreasonable. You are accustomed to having to deal with the realities in front of you and take action, not just talk about it.”

The end of the American “boomtown”: Economists are noting a drastic change from the migration patterns that once fueled the boom of major cities like Chicago, as people now flock to lower-wage metro areas instead of the more prosperous, productive cities. The big problem? Housing shortages. (New York Times)

Slim margins in Atlanta: As Democrat Keisha Lance Bottoms celebrated her victory in the Atlanta mayoral race—seemingly continuing the city’s unbroken chain of black leadership over the past 40 years—her opponent, independent Mary Norwood, is calling for a recount of the close numbers. (CNN)

Don’t walk in traffic: Air pollution from traffic fumes on city streets could negate the health benefits of walking for people over 60, according to a groundbreaking new study from Duke University and Imperial College London that suggests sticking to exercise in green spaces. (Guardian)

D.C. housing fix: Responding to threats to affordable housing in the proposed federal tax bill, D.C. Mayor Muriel Bowser has introduced her own strategy for preserving 4,000 units through private activity bonds. The announcement comes a week after the notoriously expensive city approved a new $10 million preservation fund for affordable housing. (Next City)

The urban lens:

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