Expert Commentary

The greenness of cities: C02 emissions and urban development

2008 policy brief by the Rappaport Institute and Taubman Center on carbon dioxide emissions across metropolitan and suburban areas in the United States.

Housing and automobiles in the United States generate almost 40% of the nation’s carbon dioxide emissions. Emissions vary with an area’s population density and weather patterns.  These in turn affect automotive and transit use, home heating, air conditioning and electricity usage.

A 2008 policy brief by the Harvard Kennedy School’s Rappaport Institute and Taubman Center, “The Greenness of Cities: Carbon Dioxide Emissions and Urban Development,” seeks to quantify carbon dioxide emissions across different metropolitan and suburban areas in the United States.

The researchers finds that:

  • Older and denser cities generally have significantly lower per-capita emissions than suburban areas in the same regions.
  • The city-suburb gap is particularly large in older areas, such as New York.
  • The lowest emissions areas are generally in western metropolitan areas, a consequence of their milder climate; the highest emissions areas are in southern areas of the United States, where development is spread out and air conditioning use is high.
  • If the social cost of one ton of carbon dioxide emissions is $43, the annual environmental damage associated with an additional home in Greater Houston would be more than $500 greater than a corresponding home in Greater San Francisco.
  • Current land-use regulations often push new development away from areas with low per-capita emissions and toward those with higher emissions.

Based on the policy brief, several approaches are possible to reduce carbon-dioxide emissions from the nation’s housing and automotive sectors. First, land-use controls should be adjusted to favor development in areas with low per-capita emissions. Second, a carbon tax would encourage people to internalize the social costs of their actions.

Tags: carbon, emissions, greenhouse gases, mass transit, cars, driving