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U.S. Emits Half of Car-Caused Greenhouse Gas, Study Says

American cars and pickup trucks are responsible for nearly half of the greenhouse gases emitted by automobiles globally, even though the nation's vehicles make up just 30% of the nearly 700 million cars in use, according to a new report by Environmental Defense.

Cars in the U.S. are driven more miles, face lower fuel economy standards and use fuel with more carbon than many of those driven in other countries, the authors found. According to the report by the environmental group, due out today, U.S. cars and light trucks were driven 2.6 trillion miles in 2004, equal to driving back and forth to Pluto more than 470 times.

The report's authors hope their findings will bolster efforts in Congress to require federal regulators to raise fuel economy standards for vehicles and set a mandatory cap on greenhouse gases from all sources. Numerous studies have linked carbon dioxide emissions from burning of fossil fuels such as gasoline to global warming.


In 2004, small cars emitted the highest percentage of carbon dioxide compared with other types of vehicles in the U.S., according to a report by Environmental Defense. The amount is larger because more small cars are on the road.

By vehicle class, 2004 (Figures in parentheses are in million metric tons of carbon equivalent)

Small cars (77): 25%

SUVs (67): 21%

Pickups (60): 19%

Midsize cars (54): 17%

Vans (29): 9%

Large cars (26): 8%

Note: Numbers do not add up because of rounding. Source: Environmental Defense One surprising finding was that small cars emitted more carbon dioxide than SUVs, 25% of the total compared with 21%. That is because there are more older small vehicles with higher emissions still in service, said lead author John DeCicco, a mechanical engineer specializing in automobile research.

"Even though SUVs get worse fuel economy and burn more gas, there's roughly twice as many small cars in operation," he said.

That will change in a few years based on car scrapping rates, he predicted, with SUVs bought over the last 10 to 15 years taking the lead, even if consumers begin buying small cars again because of sharply higher fuel prices.

"As Americans we're going to be living down the SUV boom for a long time," he said. "The implication is that we can't turn the emissions problem on a dimeS. It takes a generation."

The study concludes that vehicles manufactured by the nation's Big Three automakers  General Motors, Ford and DaimlerChrysler  produce the most emissions, with Toyota ranked fourth.

Nearly one-third of the emissions came from vehicles made by GM.

GM spokesman Dave Barthmuss said he had not seen the report and did not know whether the company's cars created the highest percentage of greenhouse gas emissions. But he added that if it was true, it would make sense because GM sold the most cars.

"Certainly the fact that we have the most cars on the road contributes, I'm sure, to these findings," he said. "As the world's largest automaker it's no surprise."

He said the company was committed to cutting greenhouse gas emissions through continued research and development of alternative fuels and technologies to replace gasoline and the internal combustion engine. He said the company would like to see greenhouse gases completely eliminated eventually with the development of hydrogen-powered fuel cell vehicles that could be available for commercial sale within 10 years.

Automakers said they were surprised to hear that small cars emitted more carbon dioxide than SUVs. In addition to the fact that there were more on the road, Barthmuss said, "if you get 30 miles to the gallon S people will drive more, drive farther. The more fuel efficient the vehicle, the more inclined you are to drive. And the more you drive, the more fuel you burn. It's almost a Catch-22."

DeCicco said: "We're not trying to paint a bull's-eye on GM's hideS. Everyone has a role to play, from the auto manufacturers to Joe the consumer buying a new car."

He said the study was designed to show for the first time the huge amount of carbon dioxide released by American cars and to stimulate passage of tougher laws and policies aimed at reducing it. The Senate last year passed a nonbinding resolution to cap emissions, but bipartisan efforts to pass a law have thus far failed.

Rep. Henry A. Waxman (D-Los Angeles) last week introduced a version that would freeze allowable levels of greenhouse gas emissions in 2010, reduce them by 2% each year through 2020, then reduce them further by 5% annually through 2050.

The act would achieve the targets through a cap-and-trade program along with measures to advance renewable energy, energy efficiency and cleaner cars.

Auto industry spokesmen did not respond to requests for comment on such a cap. The companies have fought efforts to pass tougher federal fuel economy standards and is suing California and several other states to block state-by-state tailpipe emission laws.

Copyright 2006 Los Angeles Times