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From John Etherington

Philip Stott was destined to be savaged by the global warming faithful (20 September, p 25). Indeed, your letter writers may even be right about Willie Soon and Sallie Baliunas going too far, and Ján Veizer and Nir Shaviv stretching their data (11 October, p 30) in their papers.

However, Gavin Schmidt gets it very wrong by equating the “demonstrable impact” of increasing carbon dioxide levels on radiation of heat from the planet, with the accuracy of prediction by climatic simulations. This single factor is simply not enough to produce an adequate predictive model when, on the Intergovernmental Panel on Climate Change’s own admission, the IPCC does not understand the role of water vapour or cloud, and cannot even say whether the net feedback is positive or negative.

Garbage in, garbage out. If the net sign of the water feedback is negative the system will homeostase. The fact that periods of intense warming and cooling, accompanied by CO₂ see-saws, have reversed 20 or more times in the Quaternary suggests that this is very likely.

James Hansen, “father” of some of the present global warming hysteria, has recently changed tack and written: “Emphasis on extreme scenarios may have been appropriate at one time, when the public and decision-makers were relatively unaware of the global warming issue. Now, however, the need is for demonstrably objective climate-forcing scenarios consistent with what is realistic under current conditions.”

It seems to me the time has come for some scientific discussion of global warming – away from the political arena, the pressures of funding bodies and the prayers of acolytes.

Llanhowell, Pembrokeshire, UK