Ed Glaeser writes in City Journal on his latest study, which suggests that cities emit less carbon than suburbs. (Full NBER paper with Matthew Kahn can be found here.) The top five cities (by emissions) are in California.
This sounds counterintuitive at first blush. But, Glaeser suggests, people who live in the suburbs drive more and consume more housing. The policy implication is make cities more affordable by loosening building restrictions:
If climate change is the major environmental challenge that we face, the state should actively encourage new construction, rather than push it toward other areas. True, increasing development in California might increase per-household carbon emissions within the state if the new development, following the current model, took place on the extreme edges of urban areas. A better path would be to ease restrictions in the urban cores of San Francisco, San Jose, Los Angeles, and San Diego. More building there would reduce average commute lengths and improve per-capita emissions. Higher densities could also justify more investment in new, low-emissions energy plants.
Similarly, limiting the height or growth of New York City skyscrapers incurs environmental costs. Building more apartments in Gotham will not only make the city more affordable; it will also reduce global warming.