DEAR SIR: John Sweeney is entitled to express his views on climate change. However accusing Matt Dempsey of playing tobacco industry tactics is misleading and grossly unfair.

He only posed the question, arising from a lecture given by a retired eminent professor of atmospheric sciences, if the science on climatic change was on a sufficiently sound basis to justify restricting Ireland’s agricultural production.

Let us pose the question as to what brought about global warming immediately after the ice age 10,000 years ago. Surely tillage operations or gas from the cow could not be held responsible. Maybe factors beyond human control such as the sun and oceans played a major part.

If so, let us adopt the null hypothesis and try to prove that this is not so but in the process we discover to the contrary. Consequently, clean energy use would have to be the focus of industrial research and agricultural research efforts would be directed to alleviating the effect of warming measures such as irrigation and the use of genetic modification.

Gene transfer from deep-rooted desert vegetation to temperate climate farm crops would, in this case, be worth considering.

If on the other hand fossil fuels and agricultural intensification were major causative factors, then research must, as a first priority, discover cheap and safe energy alternatives. The human race must be fed so it is likely that research on such crops as trees and grass, that fix carbon in equal measure, would only have a relatively small effect on climate change.