Last Sunday, the Washington Post published a piece by Joel Kotkin and Ali Modarres which sought to debunk the ideas that dense urban areas are greener than their suburban counterparts and that encouraging dense growth might play a significant role in reducing America’s carbon output. The piece was wrong or misleading on practically every point, to the extent that any complete response would take up far more time and space than I have available. Some of the authors’ most egregious errors simply must be addressed, however.

Kotkin and Modarres spend the first half of their op-ed arguing that cities contribute to negative environmental outcomes through heat-island effects. The authors acknowledge that such effects can’t be linked to global warming but warn that they necessitate increased air conditioner use, leading to greater energy consumption. They neglect to mention that the same effects should also moderate heating needs in winter.

The bigger issue, of course, is what the numbers actually say about energy use in urban areas relative to suburban areas. In fact, urban residents tend to use less energy per person than suburbanites, and the gap is largest for urban families living in dense, multifamily housing. The intuition behind this isn’t terribly difficult to grasp; urban homes tend to be smaller than suburban homes, with less surface area exposed to the air, improving the efficiency of heating and cooling. Large, shared boilers and condensers are also likely to prove more efficient than small ones scattered across many detached homes. Kotkin and Modarres argue that suburban homes can be greened more cheaply than large urban buildings, but that’s far from clear. Another story in the Post this week suggests that efficiencies can be achieved in urban buildings at zero long-term cost, and businesses are beginning to recognize that potentially profitable opportunities may exist to help green those larger structures.

The largest gap between urban and suburban emissions is generated by disparities in transportation patterns. In dense urban areas, residents can easily substitute driving with walking, biking, or using mass transit. When urbanites do drive within the city, the distances tend to be short. In suburban and exurban areas, substitutes for cars are rare. Automobiles are used for every little errand, and even short trips are long by urban standards.

Recent carbon audits give credence to the role of settlement and transportation patterns in reducing emissions. A study conducted for Greater Washington revealed that per capita transportation emissions in the metropolitan area were less than the national average. Within the Washington area, transportation emissions for the District — the densest and most transit dependent portion of the area — were far lower on a per capita basis than in the neighboring Virginia and Maryland suburbs. This despite the fact that the District is home to the area’s largest employment concentration, into which hundreds of thousands of suburban residents commute daily. Even the District’s numbers pale in comparison with the success achieved in New York City.

Kotkin and Modarres see these statistics and declare them irrelevant, because, as they say, Americans simply prefer suburban life. Absent a calamity of some sort, they suggest, Americans are unlikely to reduce their consumption of low-density life and automobile use. This is simply incorrect. Rail and transit ridership have increased substantially in recent years as congestion and fuel costs have increased. Americans appear happy to use alternative transportation options when they’re available, but are prevented from doing so more often by federal transportation policies. While some $40 billion per year in federal tax money is allocated to states, no strings attached, for highway construction and maintenance, transit projects are granted a little over $1 billion per year, and that money comes with substantial oversight and regulation as to its use. Amtrak will probably receive about $1.4 billion next year thanks to the support of dedicated Congressional backers. The Bush administration, by contrast, has consistently sought to remove Amtrak’s operating subsidy from the federal budget.

Whatever American preferences for suburban relative to urban living, there can be no question that the size of the nation’s suburban population has been artificially enlarged through poor policy choices. Disparities in transportation funding are one source of overextensive suburban growth, but there are many others. Commuters are not faced with the cost of the negative congestion and pollution externalities they impose on others. If commuters were required to pay congestion charges and pollution or emission taxes, cities would almost certainly be much denser and suburban development far less extensive. Kotkin and Modarres argue that driving and suburban development are increasing in Europe, where transit is better funded and gas taxes are much higher. Perhaps so, but they fail to mention that European cities remain much denser than their American counterparts, and Europeans emit far less carbon per capita than Americans. It’s simply dishonest to discuss the preferences of American commuters without mentioning the massive social subsidies suburbanites receive.

Improvements in urban efficiency and in suburban efficiency are fine goals. If we’re interested in significant reductions in carbon emissions, we ought to concentrate more on making the suburbs like the cities: denser, more walkable, and transit-oriented. In the end, any effective measure that we adopt to reduce carbon emissions — be it a cap-and-trade regime or a carbon tax — is going to increase the cost of driving and suburban life. This will increase the incentive for Americans to live densely and use transit or other alternative transportation modes. There’s no good reason why we shouldn’t begin helping this transition along now, by increasing transit funding and subsidizing denser development.