MICHAEL HANLON is right that government can be untrustworthy, "scientism" dubious and tax revenue badly spent ("Good excuse to clean up", Section 2, 11 January). Cars are not the only source of carbon dioxide emissions, that too is true, but I disa-gree with the rest of his article.

There is now no argument that climate change is real. Chaos theory tells us that climate is a chaotic unpredictable system. We don't know what's going to happen - that's the point.

The role of cars in CO2 emissions is increasing. Industry has tackled fuel and energy efficiency more seriously than consumers and motorists, and future emissions will come increasingly from transports. By all means apportion cuts and taxes fairly - the way forward is to be fair, not to let motorists off the hook. Motorists are not poor: 90 per cent of the better-off drive cars; 70 per cent of the poor do not.

Mr Hanlon is correct that there are two sorts of chemical pollution from cars. As well as CO2 gases there is local pollution, like that from diesel, which is a health hazard. One might call it "passive motoring" - the risks are analogous and can be worse than those from passive smoking. But the motorist faces no "thank you for not driving" notices.

Anat Kamenka Algazi