OK so now it’s official. We all knew that Americans drove gas-guzzling polluting vehicles, but now the Environmental Defence Fund has calculated just how bad things are. And they are bad.

Americans may only have 5% of the world’s population but they drive a third of its cars. However because Americans drive further in big and inefficient cars they account for 45 per cent – or nearly half – the carbon dioxide pumped out of exhaust pipes each year, according to EDF’s new report “Global Warming on the Road“.

The report found that carbon from vehicles built by the Big 3 US manufacturers (General Motors, Ford and DaimlerChrysler) each exceed the total CO2 emissions from the nation’s largest electric power companies, American Electric Power (AEP).

The American share of CO2 emissions is disproportionately higher because American vehicles are driven more each year and on average burn more fuel than cars in other countries. The average US passenger vehicle, with a fuel economy of less than 20mpg, travels 11,000 miles a year, nearly a third more than cars elsewhere. An average fuel economy of 19.6 mpg in 2004 is quite frankly pathetic.

And the trend is set to get worse. The distances traveled are getting greater: Between 1990 and 2001 the number of miles travelled on American shopping trips rose by 40%, as Americans commute more, shop more, and drive further to the shops each time.

The cars are getting bigger: SUVs will soon be the main source of CO2 emissions from U.S. autos, having overtaken small cars in market share in 2002.

The report is a graphic account of America’s addiction to oil – the crucial question is how can we turn things round??