Large cities aren’t more carbon efficient

“Are larger cities more energy and emissions efficient than smaller ones?” asks a group of researchers in a new PLOS ONE study. That pattern would make sense; after all, big cities often enjoy economies of scale. But after analyzing hundreds of US urban areas, the team concluded that carbon dioxide emissions per person don’t drop substantially as a city grows.

The researchers examined the populations of 366 metropolitan areas, which contain at least 50,000 people, and 576 “micropolitan” areas, which contain 10,000 to 50,000 people. The smallest urban area evaluated was Tallulah, Louisiana, and the biggest was the New York area. The team also analyzed each county’s CO2 emissions for 1999 to 2008.

When the number of people living in a city increases by 1 percent, CO2 emissions rise by 0.93 percent, the study authors estimate. This “near-linear relationship… suggests that large urban areas in the U.S. are only slightly more emissions efficient than small ones,” they write. — Roberta Kwok | 13 June 2013

Source: Fragkias, M. et al. 2013. Does size matter? Scaling of CO2 emissions and U.S. urban areas. PLOS ONE doi: 10.1371/journal.pone.0064727.

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