SIR - So Derek Baddeley (Letters, April 28) thinks talk of global warming is scientists defending their own jobs? This sounds like a case of 't must be true, I saw it on TV'!

Did he inquire who sponsored his documentary, I wonder? Oil companies with family members leading the US Government are the ones with the real money, vested interests and belief that pre-emptive attacks are the best way of defending one's own interests.

Admittedly, Mrs Thatcher wasn't averse to the latter, but one can hardly blame her for the views of scientists worldwide. Scientists have long been taught to believe only statistics, not what is actually happening, so their growing concern is unusual.

What confuses the issue and leaves the general public open to deception is that there can be, and often is, more than one cause of a problem. The sun may be causing global warming anyway, but demonstrably it gets warmer still inside a greenhouse, and scientific experiments have demonstrated that carbon dioxide in the atmosphere traps heat in much the same way as glass, ie high-temperature light energy can enter but cooler heat cannot so easily escape.

It is also demonstrably the case that trees absorb solar heat in the process of absorbing carbon dioxide and that more than half the world's remaining trees have been chopped or burnt down in the last 50 years. This means more heat and more carbon dioxide are being left in the atmosphere anyway.

Even if the statistics for cyclic sun-warming support the prediction that it is warming now (which we can't control), that simply makes it even more important that we do what we are able to do - stop making matters worse and try to restore the essential tree cover we are so thoughtlessly still chopping down.

D J Taylor, Malvern Link.