Sarah Clayton's letter, published last week, far from not having the space to counter all the arguments put forward by the Channel 4 programme, made not one point to support her view that global warming is irrefutably man made.

Scientific evaluation is a continuing process and must not be stifled because in some circles it is considered inconvenient or politically incorrect.

Thirty years ago, scientists were saying that it was irresponsible to advance the theory of global warning. The then current scientific view was, following three decades of declining temperatures, that the earth was heading for an ice age.

It is now accepted that we are in a period of global warming, but a number of scientists, who are not beholden to any commercial or political interests, are of the view that this is not due to man-made greenhouse gases but is the result of sunspot activity. This theory is backed by research going back several thousand years showing that ice ages coincide with periods of low sun activity and warmer temperatures with high sun activity.

I am no scientist, but surely there is room for full honest debate without rubbishing contrary views as a matter of course.

In the programme, Lord Lawson, not a scientist, but not a fool, expressed the view that the current popularly held view warrants further examination.

GB THOMPSON Seaforth Gardens Epsom