Sir - Michael Tyce (Letters, May 9) may or may not be right about wind turbines - and I suspect that he is right - but his usual rant about climate change is based on very dodgy arguments and even worse maths.

His claim that "for the last 70 years global temperatures have gone down for as many years as they have gone up", is about as relevant to the debate as the price of tea in China to an archaeological dig at Marcham.

Let's deal with these '70 years' first: human impact on the environment increases exponentially, as a result of the exponential rise in world population and the increasing industrialisation of the most populous countries, the latter effect having accelerated dramatically over the past 20 years.

What happened 70 years ago, therefore, is very much less important than what's been happening in the last quarter of a century, and only marginally more so than what happened during the Napoleonic wars.

Now let's look at the bit where he says that 'global temperatures have gone down for as many years as they have gone up'.

This is a very neat sleight of hand, if you can get away with it. In truth, it means absolutely nothing. If the temperature drops by 0.01 of a degree every single year for 99 years on the trot, and then increases by one degree during one year only, the net result is still an increase in temperature.

I don't know why Mr Tyce used the 'as many years' argument instead of claiming that overall temperatures have not gone up, although I have my suspicions; but it doesn't have a leg to stand on.

John Kinory, Steeple Aston