America’s cars and light trucks produce 20 percent of the nation’s emissions of carbon dioxide (CO2), a potent greenhouse gas that causes global warming.

If U.S. cars and light trucks were a country, they would rank fifth in the world in overall CO2 output, equaling the emissions from all sources in Japan and eclipsing those of Germany, India and Great Britain. Yet, the world’s leading automakers continue to build vehicles that produce more and more global warming pollution each year.

These findings are from a new report by Environmental Defense. The report (entitled Automakers’ Corporate Carbon Burdens) analyzes for the first time the scope of CO2 emissions produced by the U.S. fleets of the world’s leading car companies from 1990 to 2000.

The carbon burden is the amount of CO2 emitted from a group of motor vehicles, computed from a statistically predictable rate of fuel use once a vehicle leaves the showroom and is put on the road. Fuel efficiency and the amount of driving both affect the collective carbon burden. The increase in carmakers’ carbon burdens is due in part to an increase in the number of large SUVs and mini-vans that are being marketed to American consumers without corresponding improvements in fuel efficiency.

The report finds General Motors responsible for the largest overall share of CO2 emissions, accounting for 30 percent of the U.S. total for cars and light trucks in 2000. This distinction earns the auto giant the dubious title of Global Warmer Number One. Following closely on the heels of GM was Ford with 25 percent of the total and DaimlerChrysler, whose vehicles account for 18 percent of the overall carbon burden.

The report also looks at the growth of CO2 emissions by fleet. In this category, Toyota racked up a whopping 72 percent increase in CO2 emissions, due in large part to its increased sales of light trucks, while Nissan recorded the highest jump in average per-vehicle emissions. Nissan’s rising truck sales increased its average per-vehicle CO2 emissions rate by 15 percent.

Global warming pollution from cars comes from burning fuel. A gallon of gasoline weighs six pounds but when burned and combined with oxygen in the air, the resulting compound weighs nearly 20 pounds. Chrysler’s Jeep Grand Cherokee, which weighs just under two tons, emits over three times its body weight in CO2 per year.

Corporate Average Fuel Economy (CAFE) standards, which were enacted in 1975 in response to the oil crisis and OPEC embargo, made the burning of fuel by vehicles more efficient. Between 1970 and 1985, combined fuel economy rates rose from 14 miles per gallon to 25 mpg. However, light trucks were held to a different, lower standard than passenger cars, and, thus, their fuel efficiency stagnated.

As SUVs and light trucks grew in sales and market share, their lower fuel efficiency pulled the national averages down, pushing upward both carbon burdens and oil dependence. If fuel economy were improved by 5 mpg today, American consumers would save 1.5 million barrels of oil per day, more than half of what the United States imports from the Middle East.

Despite the huge share of greenhouse gases produced by their products each year, automakers have turned their attention to everything but addressing the continued rise in CO2 emissions from their cars and trucks. With their market success should come a proportionate responsibility to apply clean and efficient technology as part of the auto industry’s corporate philosophy.

Unless there is change in how automakers approach greenhouse gas emissions, corporate carbon burdens will continue to rise and the United States will continue to be locked into an unchecked demand for increasing amounts of oil. It is long past time for automakers to take a more constructive approach on this issue.

Dr. John DeCiccio is a senior fellow at Environmental Defense. For more information, visit: