to think action on climate change is destructive

[Jobless123]

Example: we are producing 'too much' CO2 (but only 1% of global total), so we introduce tax changes which result in vehicles being switched to deadly diesel, which kills tens of thousands of people in the UK each year (up to 60,000 by the latest estimate www.thesundaytimes.co.uk/sto/news/uk_news/National/article1489882.ece) A reduction to zero of UK CO2 would do nothing to stop climate change, but we are killing ourselves for a smaller reduction.

We are producing too much CO2, so we introduce mandatory biofuel quotas, which results in soaring global food prices and the consequent deaths in developing country due to unaffordable food, mass extinction of tropical fauna and flora, deforestation and destruction of tropical peat forest, rainforests, and the release of much more trapped CO2.

You're right that some environmental policies are misjudged and that you have to see the whole picture - the biofuel example is a good one.

For new vehicles, diesel car emissions are almost identical to petrol ones now, though - EU emissions standards petrol and diesel engines are now effectively identical, and diesel CO2 emissions are of course lower.

You're right that older diesel vehicles can be very polluting and it would be good to see them taken off the road, but of course most of the worst offenders are trucks and buses - classes of vehicle which have never been petrol-driven anyway.

That's not correct.

"The results for NOx in general highlight that the clearest
reductions over the past 20 or so years have been due to petrol
vehicles including petrol hybrids, where substantial reductions
have been observed with each new Euro class introduction.
b Broadly speaking, emissions from diesel vehicles of all types have
not shown significant reductions in NOx over the past two
decades, although the relative proportions of primary NO and NO2
do vary over time.
c For passenger cars, emissions of NOx for Euro 5 diesel cars are at
an equivalent level to pre-Euro vehicles (i.e. pre 1992 vehicles).
Emissions peaked for Euro 2/3 cars but are only about 25% less
for Euro 5 cars"
www.cityoflondon.gov.uk/business/environmental-health/environmental-protection/air-quality/Documents/vehicle-emission-remote-sensing.pdf

Air pollution is responsible for 1 death in 12 in London.

The death toll for diesel vehicles is roughly split 50/50 between NO2 and particulate matter. Given that NO2 emissions aren't falling, (the focus on PM reduction results in increased nitrous oxide emissions), there is fundamentally no such thing as 'clean diesel'.

We're at euro 6 now, not 5 (NOx is the big difference between euro 5 and 6).

It is certainly true that older diesel vehicles are much, much more polluting than petrol vehicles, because EU emissions legislation targeted petrol cars first. (There was a reason for this: diesel emissions control, and especially NOx control, is a very difficult technical challenge - disclaimer, catalysis is my professional field).

I'd certainly support any moves to get older diesels off the roads, and traffic restrictions for all but the cleanest vehicles. Probably the best way to improve air quality in big cities is to get people out of cars and onto bikes or public transport, and simultaneously to require retrofitting of buses and lorries to reduce pollution. Obviously this would be good for CO2 emissions too :)

Some cities are considering banning diesel fuelled vehicles. We recently changed OH's car and bought a petrol car rather than diesel for this reason.

"The average, on-road emission levels of NOX were estimated at 7 times the certified emission limit for Euro 6 vehicles. "

Jobless Then change the tests, manufacturers make cars that pass the test - make the test equivalent to sitting in city centre traffic.
Also we have not reduced the co2 footprint of this country, we have just outsourced much of it abroad.