It's not only volume brands that are reducing their average CO2 performance across their fleet, so are supercar and luxury vehicle makers, according to a report by auto consultancy JATO Dynamics that compares the average CO2 output of vehicles sold by selected specialty car brands in the first half (H1) of 2008 to the same period in 2009. With the exception of Maserati that recorded a 20g/km increase in CO2 output, all other makers included in the study showed a reduction in the average CO2 emissions of the cars they sold in the first half of 2009 compared to H1 2008.

"Of course, supercars are starting from a high base and have more scope to reduce emissions than mainstream cars, but the speed with which they are improving their CO2 performance should be credited," commented David Di Girolamo, Head of JATO Consult.

"Sales volumes might be on a smaller scale, but those manufacturers we studied sell close to 100,000 cars combined each year, and we know well that the days of supercar makers being excluded from the environmental debate are over," Girolamo added.

Ferrari showed the highest reduction in CO2 emissions as the Italian supercar maker recorded a 40.4 g/km improvement in CO2 output of new cars sold in H1 2009 over the same period in 2008.

JATO Dynamic claims that this is the greatest volume reduction of any brand on sale in Europe representing a 9.5% improvement matching that of the best performing volume brand of H1 2009 (in Europe) which is Chevrolet.

This also shows that Ferrari is well on its track to achieving its goal to trim down CO2 emissions from 400 g/km per vehicle to 280-300 g/km, by 2012.

Percentage-wise, the overall winner in CO2 volume reduction is Alpina, a German maker that sells modified BMW cars, with a 14.1% improvement over H1 2008 - although notably on a smaller scale than many of the other companies included in the study.

However, readers should be aware of a significant factor when it comes to CO emissions and that is none other than the annual km / miles covered by these specialty cars. Meaning a Ferrari or a Lamborghini may deliver for example 350g of C02 per km, but many of these cars are driven less than 30,000 km / 20,000 miles in a period of ten years. Do the math and that comes to a (theoretical) average of 7 tons of CO2.

A VW Golf 1.4 TSI 122HP with a manual transmission for example returns 144g of CO2 per km but will cover an average of around 20,000km or more per year which comes to 28.8 tons of CO2 in ten years of use (that is, if the car has been well serviced during that time).