Residents of Louisville and Lexington are among the worst contributors to climate change, according to a study of the nation's 100 largest metropolitan areas.

Researchers with Washington's Brookings Institution blame factors such as sprawling development that encourages driving rather than walking, biking or mass transit, and the cities' reliance on cheap, coal-fueled electricity.

Its list -- which measured carbon emissions per resident based on per capita emissions from residential and highway energy use in 2005 -- puts Lexington at the top of a list of offenders, and Louisville fifth.

While the ranking could be a public relations issue for leaders trying to attract industry and new residents, Louisville has made strides in recent years to improve air quality, add cycling lanes and begin a detailed study of the city's carbon output, said Bruce Traughber, the city's economic development director.

"We'll know by the end of the year, early next year what our strategies are going to be," he said. "We're going to push forward and we're going to have an impact."

The other cities with the largest population-adjusted "carbon footprints" -- Indianapolis, Toledo and Cincinnati -- have the same energy patterns that contribute to high emissions.

"These areas tend to use a lot of relatively dirty fuels for their electricity," said Andrea Sarzynski, a Brookings analyst and study co-author. "So we know the Appalachian region, for instance, relies fairly heavily on coal," which produces more carbon than other energy sources.

Western cities ranked low on the list, and researchers noted that investor-owned utilities in California no longer buy electricity from coal-powered plants.

The report also found that densely populated cities had low emissions.

Addressing the problem

Kentucky has taken strides to address energy use and conservation.

The General Assembly earlier this year passed legislation that includes incentives such as tax credits of up to $500 to help cover the cost of installing insulation, energy-efficient windows and other features.

Last month, the state's largest homebuilders began a program to encourage environmentally friendly homes.

The Brookings Institution recommends a range of policy actions on the federal, state and local levels to help cities reduce their carbon emissions.

They include promoting more transportation choices such as mass transit and developing parcels closer to city centers rather than promoting urban sprawl.

In Lexington, the city's environmental quality commissioner acknowledged in a statement that the region's economic strengths helped create its environmental weaknesses.

"For instance, our proximity to the eastern coalfields has provided us with some of the nation's lowest electrical costs," said Cheryl Taylor.

"Our central location at the intersection of two major interstates attracts significant truck traffic," she added.

Taylor said that Lexington has taken steps to reduce its carbon emissions, including limiting development outside certain boundaries.

"Our next step will be to measure our city's carbon footprint more accurately and then take even more aggressive steps to reduce it," she said.

Proactive measures

In the past year, Louisville Gas & Electric and Kentucky Utilities have signed up 920 business and residential customers to offset their coal-based electricity use with credits that subsidize hydroelectric energy produced at a plant on the Kentucky River.

"You're getting the environmental benefits from that to help the promotion and development of renewable energy," said Chris Whelan, an LG&E spokeswoman.

Louisville and Lexington are among five Kentucky cities whose mayors have signed the U.S. Conference of Mayors' climate protection agreement, striving to meet or exceed the Kyoto Protocol's target of reducing greenhouse gas emissions by 7 percent below 1990 levels by 2012.

Jackie Green, an activist who supports increasing access to public transportation, said that he believes the Brookings finding underscores his belief that Kentucky law should allow gasoline taxes to be spent on public transportation.

"TARC still has no dedicated funding we can depend on for operations year in and year out," he said.

Building new roads, such as the $4.1 billion Ohio River Bridges Project, won't help cities reduce their carbon footprint, Mark Muro, public policy director for Brookings' Metropolitan Policy Program, said.

Traughber defended the project, saying that economic development and reducing carbon emissions are part of a balancing act.

"If we can't move freight across the Ohio River in an expeditious fashion … you may have a little lower carbon footprint, but you've got a lot lower standard of living, and I'm not sure that's where the citizens of Louisville want to be," he said.

Incomplete picture

The Brookings study is a snapshot of carbon emissions in Louisville and other large metropolitan areas, but it stops short of addressing the impact from heavy industry and commercial buildings, for example.

In their report, researchers estimated personal vehicle and freight travel on highways within metro areas, and they also gauged those areas' electricity use based on statewide averages of the carbon output associated with electricity.

"These two sources of carbon are two of the largest sources of carbon emissions and they represent about half of the CO2 emitted in the U.S. today," said researcher Marilyn A. Brown, a public policy professor at the Georgia Institute of Technology.

Reporter Marcus Green can be reached at (502) 582-4675.