Urban areas around the world account for an estimated 71 percent of energy-related greenhouse gas emissions (including everything from power plants to automobile driving). But a new study found that big-city metros differ markedly in how much they pollute.

In a study published earlier this year in the journal Environment & Urbanization, researchers at the World Bank in Washington, D.C., found that New York City had less than half the per-capita greenhouse gas emissions of Denver, Colorado, and Los Angeles—considered by some to be the smog capital of the country—had lower per-capita emissions than Minneapolis, Minnesota. Outside the United States, some of the largest urbanized centers, such as Tokyo, Paris, and even Seoul, had some of the lowest per-capita greenhouse gas emission rates in the world.

Why? The researchers discovered some important trends: Lower per-capita emissions typically were found in dense urban areas with good transportation systems and in warmer climates. That helps explain why sunny L.A. performed better than chilly Minneapolis. Digging even deeper into their data, the researchers determined that dense, more urban sections of Toronto had lower emissions than single-family-housing-oriented suburbs.

In the future, as greenhouse gas reduction policies gain momentum at the federal and metropolitan levels, this new study could have implications for real estate development among ULI members. First, the larger, denser, and warmer metro areas may actually accommodate more new development, because of per-capita emissions levels that are lower than the U.S. average. Second, more sprawling metropolitan areas may eventually incentivize denser new developments as a way to curb the growth of greenhouse gas emissions.

Below are the top ten lowest-polluting big-city metro areas in the United States, according to the World Bank researchers:

Rank

Major Metro

Carbon Emissions (Tons per Capita)

1

San Francisco

10.1

2

New York City

10.5

3

Philadelphia

11.1

4

San Diego

11.4

5

Miami

11.9

6

Chicago

12.0

7

Portland, Oregon

12.4

8

Los Angeles

13.0

9

Boston

13.3

10

Seattle

13.7

                                                                      Source: Environment & Urbanization journal.