Hot World? Blame Cities.

By Joel Kotkin and Ali Modarres
Sunday, October 14, 2007

It's all the suburbs' fault. You know, everything -- traffic congestion, overweight kids, social alienation. Oh, and lest we forget, global warming and rising energy costs, too.

That latest knock against the burbs has caught on widely. With their multiplying McMansions and exploding Explorers, the burbs are the reason we're paying so much for gas and heating oil and spewing all those emissions that are heating up the atmosphere -- or so a host of urban proponents tells us. It's time to ditch the burbs and go back to the city. New York, Boston, Chicago -- these densely packed metropolises are "models of environmentalism," declares John Norquist, the former Milwaukee mayor who now heads the Congress for a New Urbanism.

But before you sell your ranch house in Loudoun County and plunk down big bucks for that cozy condo in the District, take a closer look at the claims of big cities' environmental superiority. Here's one point that's generally relegated to academic journals and scientific magazines: Highly concentrated urban areas can contribute to overall warming that extends beyond their physical boundaries.

Studies in cities around the world -- Beijing, Rome, London, Tokyo, Los Angeles and more -- have found that packed concentrations of concrete, asphalt, steel and glass can contribute to a phenomenon known as "heat islands" far more than typically low-density, tree-shaded suburban landscapes. As an October 2006 article in the New Scientist highlighted, "cities can be a couple of degrees warmer during the day and up to 6¿ C [11 degrees Fahrenheit] warmer at night." Recent studies out of Australia and Greece, as well as studies on U.S. cities, have also documented this difference in warming between highly concentrated central cities and their surrounding areas.

This is critical as we deal with what may well be a period of prolonged warming. Urban heat islands may not explain global warming, but they do bear profound environmental, social, economic and health consequences that reach beyond city boundaries. A study of Athens that appeared this year in the journal Climatic Change suggested that the ecological footprint of the urban heat island is 1 1/2 to two times larger than the city's political borders.

Further, urban heat islands increase the need for air conditioning, which has alarming consequences for energy consumption in our cities. Since air conditioning systems themselves generate heat, this produces a vicious cycle. Some estimate that the annual cost of the energy consumption caused by the urban heat island could exceed $1 billion.

This is not to say that big buildings can't be made more energy efficient by using new techniques, such as high-tech skin designs, special construction materials to reduce energy consumption, green roofs and passive cooling. But one big problem is that making large buildings green also makes them much more expensive, so that they're less and less affordable for middle-class and working-class families.

Low-density areas, on the other hand, lend themselves to much less expensive and more environmentally friendly ways of reducing heat. It often takes nothing more than double-paned windows to reduce the energy consumption of a two- or three-story house. Shade can bring it down even further: A nice maple can cool a two-story house, but it can't quite do the same for a 10-story apartment building.

Focusing on the suburbs has the added virtue of bringing change to where the action is. Over the past 40 years, the percentage of people opting to live in cities has held steady at 10 to 15 percent. And since 2000, more than 90 percent of all metropolitan growth -- even in a legendary new planners' paradise such as Portland, Ore. -- has taken place in the suburbs.

So we shouldn't be trying to wipe out suburbs. Even with changes in government policy, it would be hard to slow their growth. Europe has strict zoning and highly subsidized mass transit -- policies that are supposed to promote denser development -- but even so, their cities are suburbanizing much like American ones. "Sprawl cities," notes Shlomo Angel, an urban planning expert at the Woodrow Wilson School at Princeton University, also are becoming ever more common throughout much of Asia and the developing world.

Here's an Earth-to-greens message: Instead of demonizing the suburbs, why not build better, greener ones and green the ones we already have?

One approach might be to embrace what one writer, Wally Siembab, has dubbed "smart sprawl." Encouraging this sort of development will require a series of steps: reducing commuters' gas consumption with more fuel-efficient cars, dispersing work to centers close to where workers live and promoting continued growth in home-based work. We'll also have to protect open spaces by monitoring development and establishing land conservation based on public and private funding, the latter coming from developers who wish to work in suburbs.

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