To save the planet, build more skyscrapers—especially in California

Green Cities, Brown Suburbs. By Edward L. Glaeser
To save the planet, build more skyscrapers—especially in California.
http://www.city-journal.org/2009/19_1_green-cities.html

On a pleasant April day in 1844, Henry David Thoreau—the patron saint of American environmentalism—went for a walk along the Concord River in Massachusetts. With a friend, he built a fire in a pine stump near Fair Haven Pond, apparently to cook a chowder. Unfortunately, there hadn’t been much rain lately, the fire soon spread to the surrounding grass, and in the end, over 300 acres of prime woodland burned. Thoreau steadily denied any wrongdoing. “I have set fire to the forest, but I have done no wrong therein, and now it is as if the lightning had done it,” he later wrote. The other residents of Concord were less forgiving, taking a reasonably dim view of even inadvertent arson. “It is to be hoped that this unfortunate result of sheer carelessness, will be borne in mind by those who may visit the woods in future for recreation,” the Concord Freeman opined.

Thoreau’s accident illustrates a point that is both paradoxical and generally true: if you want to be good to the environment, stay away from it. Move to high-rise apartments surrounded by plenty of concrete. Americans who settle in leafy, low-density suburbs will leave a significantly deeper carbon footprint, it turns out, than Americans who live cheek by jowl in urban towers. And a second paradox follows from the first. When environmentalists resist new construction in their dense but environmentally friendly cities, they inadvertently ensure that it will take place somewhere else—somewhere with higher carbon emissions. Much local environmentalism, in short, is bad for the environment.

Matthew Kahn, a professor of economics at UCLA, and I have quantified the first paradox. We begin by estimating the amount of carbon dioxide that an average household would emit if it settled in each of the 66 major metropolitan areas in the United States. Then we calculate, for 48 of those areas, the difference between what that average household would emit if it settled in the central city and what it would emit in the suburbs. (The remaining 18 areas had too little data for our calculations.) A few key points about our methodology follow; if you’re interested in all the methodological details, click here.

First, by “average household,” we mean average in terms of income and family size, so that we aren’t comparing urban singles with large suburban families. However, we don’t want to standardize the physical size of the home. People who move to suburban Dallas aren’t likely to live in apartments as small as those in Manhattan. Smaller housing units are one of the important environmental benefits of big-city living.

Second, we try to estimate the energy use from a typical new home in an area—specifically, one built in the last 20 years—which sometimes means something quite different from an average one. The reason is simple. We aren’t playing a ratings game to figure out which city pollutes least; rather, we’re trying to determine where future home construction would do the least environmental damage.

We calculate carbon emissions from four different sources: home heating (that is, fuel oil and natural gas); electricity; driving; and public transportation. Residential energy use and non-diesel motor fuel are each responsible for about 1.2 billion tons of carbon dioxide emissions each year, out of total U.S. emissions of 6 billion tons. So these sources together reflect about 40 percent of America’s carbon footprint. Our procedure is admittedly imperfect and incomplete: for example, we do not include carbon dioxide generated as a by-product of workplace activity.

The table below shows some of the results of our research. The five metropolitan areas with the lowest levels of carbon emissions are all in California: San Francisco, San Jose, San Diego, Los Angeles, and Sacramento. These areas have remarkably low levels of both home heating and electricity use. There are cold places, like Rochester, that don’t air-condition much and thus use comparably little electricity. There are warm places, like Houston, that don’t heat much and thus have comparably low heating emissions. But coastal California has little of both sorts of emissions, because of its extremely temperate climate and because California’s environmentalists have battled for rules that require energy-efficient appliances, like air conditioners and water heaters, and for green sources of electricity, such as natural gas and hydropower. (Some analysts argue that this greenness is partly illusory—see “California’s Potemkin Environmentalism,” Spring 2008—but certainly, by our measures, California homes use less energy.) Also, despite the stereotypes about California highways and urban sprawl, some of these five cities, like San Francisco, have only moderate levels of transportation emissions, since their residents actually live at relatively high densities, which cuts down on driving.

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Edward L. Glaeser is a professor of economics at Harvard University, a City Journal contributing editor, and a Manhattan Institute senior fellow. His article describes research jointly performed with Matthew Kahn of UCLA.