claim: The warmer the planet gets, the more ozone forms, and by mid-century, Americans will likely suffer a 70 percent increase in unhealthy ozone smog, the National Center for Atmospheric Research has projected.
evidence: According to the same report, the city experienced a significant reduction in high ozone days since 2001—from nearly 50 days per year to fewer than 10—along with fewer days of high particle pollution since 2000—from about 19 days per year to about 3—and an approximate 30% reduction in annual levels of particle pollution since 2000.