Large metro areas offer greater energy and carbon efficiency than nonmetropolitan areas, and metro areas have development patterns that show promise for reducing carbon emissions, according to a new report (PDF) from The Brookings Institution. The report quantifies transportation and residential carbon emissions for the 100 largest U.S. metropolitan areas carbon profiles of the 100 here), finding that metro area residents have smaller carbon footprints than the average American, although metro footprints vary widely.
Analysis of the partial carbon footprints (the footprints do not include emissions from commercial buildings, industry, or non-highway transportation) reveals five major findings:
1. Large metropolitan areas offer greater energy and carbon efficiency than non metropolitan areas
Despite housing two-thirds of the nation's population and three-quarters of its economic activity, the nation's 100 largest metropolitan areas emitted just 56 percent of U.S. carbon emissions from highway transportation and residential buildings in 2005. Therefore, the average metro resident in 2005 had a smaller carbon footprint (2.24 metric tons) than the average American (2.60 metric tons). The difference stems primarily from less car travel and electricity use.
2. Carbon emissions increased more slowly in metropolitan America than in the rest of the country between 2000 and 2005
Carbon emissions from highway transport and residences in major metro areas increased 7.5 percent from 2000 to 2005, slightly less than the national increase of 9.1 percent. The population of the 100 metro areas, on the other hand, grew by only 6.3 percent. As a result, the average per capita footprint of the 100 metro areas grew by only 1.1 percent during the five-year period, while the U.S. partial carbon footprint increased twice as rapidly (by 2.2 percent) during this same timeframe.
3. Per capita emissions vary substantially by metro area
In 2005, per capita carbon emissions were highest in Lexington, KY, and lowest in Honolulu. The average resident in Lexington emitted 2.5 times more carbon from transport and residences than the average resident in Honolulu, at 3.46 metric tons compared with 1.36 metric tons. This variation is even more striking when adjusting for a metro area's economic output, or gross metropolitan product -an indicator of carbon intensity.
4. Development patterns and rail transit play an important role in determining carbon emissions
Density, concentration of development, and rail transit all tend to be higher in metro areas with small per capita footprints. Much of what appears as regional variation may be attributed to these spatial factors. Dense metro areas such as New York, Los Angeles, and San Francisco stand out for having the smallest transportation and residential footprints.
5. Other factors are important, such as the fuels used to generate electricity, electricity prices, and weather
The fuel mix used to generate electricity matters in residential footprints. A high-carbon fuels mix significantly penalizes the Ohio Valley and Appalachian regions, which rely heavily on coal power. Alternatively, hydro-reliant metro areas such as Seattle have substantially smaller residential footprints. Each of the 10 metro areas with the lowest per capita electricity footprints in 2005 hailed from states with higher-than-average electricity prices.
According to Brookings, Federal policy could play a powerful role in helping metropolitan areas-and so the nation-shrink their carbon footprint further. In addition to economy-wide policies to motivate action, five targeted policies are particularly important within metro areas and for the nation as a whole:
