Los Angeles has suffered the worst ozone pollution of any American city for three years running.

Coastal areas of the city could be swallowed by the Pacific by the end of the century as a warming climate causes sea levels to rise. A natural gas leak in northwestern Los Angeles, finally plugged in February, was the most disastrous in American history.

Small wonder that Los Angeles is joining a growing movement to confront environmental challenges at the local level. As the former New York mayor Michael Bloomberg realized early in his tenure, cities, with their concentrated populations, can play an important role in addressing local air pollution as well as global climate change. (Mr. Bloomberg helped to lead a delegation of mayors from various countries at last December’s global climate summit meetings in Paris, and their presence had much to do with pushing a final agreement over the finish line.)

Moreover, it has proved easier to act locally than to push legislation through Congress, many of whose members publicly question the existence of human-caused climate change, and whose recalcitrance has forced President Obama to use his executive powers to get anything done on climate change or, for that matter, any environmental issue.

Last month, the Los Angeles City Council took an important step toward getting 100 percent of the city’s energy from renewable sources. It is only at the beginning of the process. There is no timeline, but the Department of Water and Power has been ordered to study how the city could reach that goal.