PHIL Roe (Warming blame, letters, November 14) reckons it's okay to continue belching out CO2 from large cars because volcanoes belch out more.

Unfortunately, science proves him wrong. Since he's asking for experts who can disprove his arguments, I'd be happy to point him at the NASA and Penn State University crew at www.realclimate.org, who will set out the science for him.

We can demonstrate that increased CO2 in the atmosphere - and the climate change it brings - is due to human activity, by measuring carbon isotopes which show the origins of CO2 in the atmosphere and can trace it to the burning of fossil fuels.

There is plenty more such evidence if you choose to look for it.

As for depletion of ozone at the Antarctic, it will take around 20 years to recover from the damage caused by CFCs, and occasional climatic variations will cause highs and lows.

"Conclusive proof" is complex. We rely on statistics and analysis of often unclear evidence. Pretty much all of this now points to links between our activity and climate change. Only the ostriches such as Mr Roe seem determined to go out of their way to ignore it.

Phil Bixby, Constructive Individuals, Holgate Road, York.