Fighting Global Warming Block by Block

Several environmental and planning experts warned that unless cities and counties take active steps to limit sprawl now, the United States will find it nearly impossible to make deep cuts in greenhouse-gas emissions in the decades to come. Sims, who testified before the Senate Environment and Public Works Committee in November, noted that because people are commuting greater distances each year, the increase in carbon-dioxide emissions from transportation by 2030 will far outpace any gains the country makes in fuel efficiency.

Compact development, by contrast, could reduce metropolitan carbon-dioxide emissions by roughly 20 percent, said Reid Ewing at the University of Maryland's National Center for Smart Growth.

The goal of land-use planners is not to cut emissions right way, recognizing that it will take decades for that to happen, but to ensure that development doesn't drive up a region's greenhouse-gas output.

"Once you've sprawled, it's really hard to overlay more efficient transportation systems," said Judi Greenwald, director of innovative solutions at the Pew Center on Global Climate Change. "Everybody realizes that this is a big piece of this, but everybody realizes this is really hard."

Even as some states in the Northeast and West are working aggressively to curb their greenhouse-gas emissions, the proliferation of exurbs in the Southeast is exacerbating the problem. Six Southeastern states -- Alabama, Georgia, North Carolina, South Carolina, Tennessee and Virginia -- would rank as the world's seventh-biggest emitter if they were a single country.

"This region is a major part of the problem," said Oliver A. "Trip" Pollard, land and community program leader at the Southern Environmental Law Center. "So far, we are not a major part of the policy solution."

As the Southeast continues to grow -- North Carolina, with a population of 8 million, is projected to add another 4 million residents in the next 20 to 25 years -- people are spreading out rather than concentrating in cities, which translates into longer commutes.

Ewing has calculated that residents of Atlanta and Raleigh drive more than 30 miles a day per person, while Boston and Portland, Ore., residents drive less than 24 miles a day in their more compact cities. More compact development could cut the U.S. transportation sector's greenhouse-gas emissions by 7 to 10 percent, Ewing and his co-authors write in their new book, "Growing Cooler."

North Carolina, which has a climate change commission, has opened a light-rail line in Charlotte that has attracted more than 30 percent more riders than planners had expected. The state is planning to spend another $2 billion on public transit, though that figure still pales in comparison to the amount it intends to spend on highways.

Most other Southeastern states are accelerating their carbon emissions by expanding roads and curtailing public transit projects. Officials are planning to expand a highway in northwest Atlanta to 23 lanes, even as they missed a deadline to install new commuter rail lines.

In the Seattle area, by contrast, voters defeated a ballot initiative in November, even though it included money for light rail, because it also provided money for highway projects. Sims, who lobbied against the measure, said it was impossible to reconcile the initiative with the region's climate goals.

"If you look at it, it would increase emissions," he said. "Why would we make an investment that would actually increase emissions?"