Besides Toyota Motor and BMW, automakers haven't done a great job of building fleets that emit less carbon dioxide, according to an Environmental Defense report.
The organization's 80-page report, called "Automakers' Corporate Carbon Burdens" (PDF), evaluated the carbon dioxide emissions of vehicles from major automakers between 1990 and 2005. Companies graded were: Ford Motor, General Motors, DaimlerChrysler, Toyota, Honda Motor, Nissan Motor, Hyundai Motor, Kia Motors, Volkswagen, BMW, Subaru and Mitsubishi Motors.
"The rate of carbon dioxide emissions from new cars and light trucks in the U.S. dipped for the first time in two decades, but their overall contribution to global warming has continued to grow steadily since 1990," Environmental Defense said in a statement.
BMW achieved a 12 percent reduction in carbon dioxide emissions across its entire fleet of cars, more than any of the other car companies included in the study. Environmental Defense attributes the drop to the company's addition of the low carbon dioxide-emitting Mini Cooper to its lineup, as well as efficiency improvements made across its entire line of cars.
Toyota was rated the second best, reducing carbon dioxide emissions by 3 percent overall during that period, due in large part to its introduction of the Prius hybrid to its lineup and efficiency improvements made to the Corolla.
The report also rated the overall "carbon burden" that automakers placed on the environment, based on factors that included the emissions of their cars and the number of cars sold.
In this area, GM ranked No. 1, with a 6.5 percent reduction in overall carbon burden. Environmental Defense, however, attributed this to GM's loss of market share, not to the carbon dioxide emissions of its overall lineup, which actually rose 3 percent. In contrast, Toyota, while low in its 3 percent carbon dioxide emissions reduction rate, grew its carbon burden by 125 percent, due to an increase in overall sales.
Environmental Defense combined the average over an entire lineup of cars and light trucks from 1990 to 2005 to determine an automaker fleet's average carbon dioxide emissions rate:
BMW, reduced 12.3 percent.
Toyota, reduced 3 percent .
Volkswagen, up 1.3 percent.
Subaru, up 1.6 percent.
General Motors, up 3 percent.
Mitsubishi, up 4 percent.
Honda, up 4.4 percent.
Ford, up 4.7 percent.
DaimlerChrysler, up 4.8 percent.
Nissan, up 9.2 percent.
Hyundai, up 17 percent.
Kia, up 30 percent.