This is a brief presentation of a new study on suburbanization and carbon footprint in dense cities. I read it on Pando.sc and, although I don't have access to the full journal article, I think that these results are very important in terms of sustainable development of urban areas. We shouldn't however jump to opposite conclusions ("what? now they tell us to build high and densely?"), because obviously sustainable city dwelling doesn't correspond to what we see in many cities such as Athens (high blocks of flat and areas where people live like sardines!)... So, "no, they probably just tell you to walk to work"... 

Spatial Distribution of U.S. Household Carbon Footprints Reveals Suburbanization Undermines Greenhouse Gas Benefits of Urban Population Density

This new study out of UC Berekely's Renewable and Appropriate Energy Laboratory shows that while US population-dense cities contribute less greenhouse-gas emissions per person than other areas of the country, these cities’ extensive suburbs essentially wipe out the climate benefits.  The 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.
 
Christopher Jones *† and Daniel M. Kammen *†‡§
†Energy and Resources Group, ‡Goldman School of Public Policy, and §Department of Nuclear Engineering, University of California, Berkeley, California 94720, United States
Environ. Sci. Technol., Article ASAP
DOI: 10.1021/es4034364
Publication Date (Web): December 13, 2013
Copyright © 2013 American Chemical Society
 

Abstract
 
Which municipalities and locations within the United States contribute the most to household greenhouse gas emissions, and what is the effect of population density and suburbanization on emissions? Using national household surveys, we developed econometric models of demand for energy, transportation, food, goods, and services that were used to derive average household carbon footprints (HCF) for U.S. zip codes, cities, counties, and metropolitan areas. We find consistently lower HCF in urban core cities (40 tCO2e) and higher carbon footprints in outlying suburbs (50 tCO2e), with a range from 25 to >80 tCO2e in the 50 largest metropolitan areas. Population density exhibits a weak but positive correlation with HCF until a density threshold is met, after which range, mean, and standard deviation of HCF decline. While population density contributes to relatively low HCF in the central cities of large metropolitan areas, the more extensive suburbanization in these regions contributes to an overall net increase in HCF compared to smaller metropolitan areas. Suburbs alone account for 50% of total U.S. HCF. Differences in the size, composition, and location of household carbon footprints suggest the need for tailoring of greenhouse gas mitigation efforts to different populations.