In fact, cities in the Western United States ranked high in the study. Los Angeles had the second-lowest carbon output per person out of the largest 100 cities studied, second only to Honolulu.
Las Vegas ranked 18th overall, with per capita carbon emissions of just over 2 metric tons. The smaller the carbon emissions, or carbon footprint, the smaller the negative impact on the environment.
"This is a relatively encouraging starting point," said Mark Muro, a senior policy analyst at the Brookings Institution, the nonprofit, independent research and policy institute that performed the analysis.
He used the word "relatively" often when discussing the study, and there are some important caveats.
The study only measured residential traffic and energy use and didn't include commercial or industrial uses, so the output of the tourist industry isn't included. That's expected to be added soon.
And while Las Vegas was ninth best in transportation carbon output, the area fell to 33rd in terms of residential energy use, most likely because of air conditioning use in the summer.
Still, there turns out to be a stark regional divide. Western cities have a much smaller carbon footprint than many Midwestern and East Coast cities.
"It forces people to look at places differently, and it is -- to some -- surprising that Las Vegas and Los Angeles rank as highly as they do," Muro said.
But, he said, "It's a startling number, and it does underscore the enormity of this problem. An individual is responsible for tons of carbon."
Muro cited several reasons why Western cities fared well:
• More new construction, which "is often more efficient than drafty older buildings."
• Mild winters, which lead to lower utility bills in the winter months.
• Denser development. "Los Angeles, Phoenix and Las Vegas are three of the densest metropolitan areas. It's relatively efficient sprawl," he said.
• More use of renewable energy, such as solar, wind, geothermal and hydropower.
About 9 percent of the valley's power comes from renewable sources, according to a Nevada Power representative. Roughly 50 percent to 60 percent comes from natural gas, and coal power accounts for a quarter of the total.
The Brookings Institution report says the federal government needs to do more to promote energy efficiency and reduced emissions. For example, existing policies tend to favor building more roads instead of beefing up public transit.
"Washington needs to loosen up and get out of the way, and reward good actions," Muro said. "Metro areas are doing a good job responding to these issues."
Local government responses include using alternative-fuel vehicles and promoting energy efficiency.
Eighty-one percent of Clark County's vehicle fleet is considered an alternative fuel vehicle that uses compressed natural gas, biodiesel or hybrid technology. The county is also trying to encourage building owners to buy 20 percent less power from the energy grid by 2015.
The city of Las Vegas has won awards for its alternative fuel program, which includes a hydrogen fueling station, two hydrogen powered buses and two hydrogen fuel cell cars.
In Henderson, 90 percent of the city's nonemergency vehicles use alternative fuel or are low emission.
Both Las Vegas and Henderson have backed a building standard called LEED, or Leadership in Energy and Environmental Design, which emphasizes energy and water conservation.
Henderson Mayor Jim Gibson said earlier this year that the city will build a 45-acre solar panel array on city-owned land, and the city is upgrading its buildings to cut electricity, water and gas use by 25 percent to 50 percent.
The city of Las Vegas, meanwhile, announced Tuesday that thermostats in City Hall will be raised "a degree or two" to save energy and as much as $6,000 a month.
And if you're worried about city employees getting stuffy, don't -- there will be a relaxed dress code through Labor Day for those who normally wear suits and ties.
Contact reporter Alan Choate at email@example.com or 702-229-6435.