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.
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 dime.... 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."
