ALAN Sangster and Bob Downie (Letters, February 21) need not worry about the effects of climate change caused by CO2 emissions as a result of burning coal because there will none of it left to burn by 2047.

Confirmed coal reserves at the end of 2006 were put at 909 billion short tons and by the end of last year almost 10 per cent went up in smoke; by 2036 more than half these reserves will have gone and, if coal-producing countries do not resort to hoarding, all 909 billion short tons will be gone for ever by the Summer of 2047. Gas will run out shortly after that as demand soars. Then what?

Do we put our faith in burning trees (aka woody biomass) or in billions of ineffectual windmills that will not work anyway without being connected to a firm secure supply of non-intermittent thermal electricity? We could go down the nuclear route, but all the coal-fired thermal power stations in the world will need to be replaced by 2040 at the very latest before exporters start to hoard their dwindling supplies of fossil fuels.

Time is of the essence and, unless we wise up and act now, all utility grids across the planet will start to stress in 20 years and crash a few short years after that.

Andrew H Mackay,

Causewayside, Glenaldie, Tain.