SIR - Yes, the sun has been shining on the Earth for some four to five billion years but mankind has had only a limited opportunity to observe its behaviour.

What we do know is that, recently, there has been a reduction in the heat reflected back into space due to changes in the atmosphere.

Volcanic activity actually increases reflection of heat by throwing up vast clouds of dust. This cools the Earth as was found after the eruption of Krakatoa (correct).

The problem with dealing with global warming is that the actions needed include prohibitions and restrictions so unpopular that they could not survive in a democracy without some enormous shift in our sense of social responsibility.

The result is that we are getting right-wing solutions of direct taxation that hurt the poor but have little effect on the habits of the rich who like to pretend they can offset their carbon footprint'.

In one sense it does not matter what is warming the Earth. The economic cost of it is going to be horrendous and it will have to be paid for.

Peter Bolton, Middlefield Court, East Morton