Carbon Emission Gains Made by Cities Canceled Out by Their Suburbs

With their heavy reliance on public transportation and closet-size apartments, cities are well established as the lowest contributors to greenhouse gas emissions per person than any other area in the country - but there's a catch. According to a new study led by researchers from the University of California, Berkeley, the extensive web of suburbs that cities give way to cancels out their carbon savings.

The study, published in the journal Environmental Science & Technology, used 37 variables, including local census and weather, to estimate households' carbon footprint. The results showed that, despite accounting for less than half of the nation's population, suburbs are responsible for about 50 percent of all household emissions, which are largely comprised of carbon dioxide.

"Metropolitan areas look like carbon footprint hurricanes, with dark green, low-carbon urban cores surrounded by red, high-carbon suburbs," said Christopher Jones, a doctoral student working with Kammen in the Energy and Resources Group. "Unfortunately, while the most populous metropolitan areas tend to have the lowest carbon footprint centers, they also tend to have the most extensive high carbon footprint suburbs."

The average carbon footprint of households living at the center of large, populous cities was about 50 percent below the norm, while those in the suburbs were up to twice the average, the findings showed. Based on this, the researchers concluded that large metropolitan areas actually have a slightly higher average carbon footprint than smaller metro areas.

"Population dense suburbs also tend to create their own suburbs, which is bad news for the climate," Jones said.

If things are to change, the researchers argue that climate solutions have to be paired with the right demographic, and that doing so won't only save on an area's emissions.

"Suburbs are excellent candidates for a combination of solar photovoltaic systems, electric vehicles and energy-efficient technologies," said Daniel Kammen, the director of the Renewable and Appropriate Energy Laboratory. "When you package low carbon technologies together you find real financial savings and big social and environmental benefits."

Curious about your own area? Check out the researchers' interactive map here.