It will not have escaped readers of this website that there has been a lot of anti-diesel-car propaganda circulating recently, especially with regard to nitrogen oxide and particulate emissions.
It is difficult to understand why. Diesel cars are cleaner now than they have ever been; Euro-6 diesels emit hardly any pollution at all.
Take a look at these graphs:
It is clear from these graphs that there is not a problem. Why, then, is diesel being demonised?
A much larger quantity of nitrogen oxide pollution in cities is caused by industrial activity and by commercial and domestic heating, not cars. Diesel cars make a very minor contribution. Domestic cookers and central heating systems both emit appreciable amounts of nitrogen oxides. I notice no-one has told us to stop cooking or heating our homes.
This is another example of a policy being promoted without proper reason.
The BBC then assists by broadcasting propaganda to persuade us that the decision was right all along.
Here is a graph of the source of NOx emissions in Greater London in 2010. I am indebted to the Policy Exchange website for the diagram.
NRMM(non-road mobile machinery) + Industrial + Non-domestic Gas + Domestic Gas comes to:
10 + 7 + 8 + 13 = 38% of the total.
Diesel car contribution comes to:
.11 x .45 = 4.95% of the total.
Petrol car contribution is
.07 x .45 = 3.15% of the total.
The total road transport contribution is 45% in the diagram, but this was 7 years ago. There have been significant advances in engine cleanliness since then; both for petrol and diesel.
The 'anti-diesel' campaign will result in fewer diesel cars. However, NOx levels won't fall very far; car-diesel NOx is only 5% to start with.
Petrol cars will be bought as replacements for diesels, so petrol NOx will go up from its present 3%.
The reduction in overall NOx levels, even if every diesel car was replaced by petrol, would be a lot less than 5%.
I haven't done the sums, but I suspect that you could get a bigger NOx reduction by getting the public to turn down their central heating thermostats by 2 degrees.
Think of the waste of resources encouraged by this scheme: thousands of perfectly good diesel cars with plenty of life left in them will be turned into scrap.