For decades Americans have fled densely populated cities; today they’re looking better all the time. A new survey of 100 metropolitan areas by the Brookings Institution finds that their per capita carbon footprint from transportation and residential energy use is 14 percent lower than the national average. Honolulu had the best rating, but the runner-up may come as a surprise—Los Angeles–Long Beach–Santa Ana,  California. The worst offender: Lexington–Fayette, Kentucky.