Taking into account the impact of all urban and suburban residents, large metropolitan areas have a slightly higher average carbon footprint than smaller metro areas.
Developing sustainable cities
"A number of cities nationwide have developed exceptionally interesting and thoughtful sustainability plans, many of them very innovative," Kammen said. "The challenge, however, is to reduce overall emissions. Chris and I wanted to determine analytically and present in a visually striking way the impacts and interactions of our energy, transportation, land use, shopping, and other choices. Cities are not islands: they exist in a complex landscape that we need to understand better both theoretically and empirically."
The UC Berkeley researchers found that the primary drivers of carbon footprints are household income, vehicle ownership and home size, all of which are considerably higher in suburbs. Other important factors include population density, the carbon-intensity of electricity production, energy prices and weather.
"Cities need information on which actions have the highest potential to reduce greenhouse gas emissions in their communities," explained Kammen. "There is no one-size-fits-all solution."
Efforts to increase population density, for example, appear not to be a very effective strategy locally for reducing emissions. A 10-fold increase in population density in central cities yields only a 25% reduction in greenhouse gas emissions.
"That would require a really extraordinary tran
|Contact: Robert Sanders|
University of California - Berkeley