A decline in the number of diesel cars would not jeopardise CO2 targets – in fact it would make them cheaper to achieve
The UK Society of Motor Manufacturers blamed February’s rise in the average new-car CO2 emissions on an “anti-diesel agenda [that] has set back progress on climate change”. Petrol v diesel cars is often presented as a trade-off between health-harming air pollution and climate-harmful CO2. Diesel cars do more miles to the litre than petrol, but this exaggerates the difference in CO2 emissions since one litre of diesel contains more energy and more carbon than one litre of petrol. If fuel were taxed on energy and carbon, rather than volume, then the tax on diesel would be 10 to 14% greater than that on petrol.
The International Council on Clean Transportation points out that petrol engines and petrol-hybrids have improved faster than diesel and will continue to do so. They conclude that a decline in diesel cars from around 56% to 15% would not jeopardise EU CO2 targets. Instead, it would make the targets cheaper to achieve since petrol engines cost less to make and have simpler exhaust clean-up. The future might be electric cars (or better yet for public health: cycling, walking and public transport), but in the short term new petrol cars, instead of diesel, might help both climate change and air pollution.