Sir, Lord Leach of Fairford’s letter (“The false certainties of climate change theory”, Dec 20) espouses a bizarre mixture of half-truths and misinformation. I find it entertaining that someone who in previous correspondence claims to be a non-scientist can so confidently list a series of “facts” that are wrong. The evidence for human-driven climate change is overwhelming: the world is warming up because of elevated greenhouse gases, the climate models can explain the cooling of the mid-20th century and if anything, projections for the future are conservative; reconstructions of the past imply the climate system is more sensitive to greenhouse gases than we might like to acknowledge.

No one is denying that scientists should be sceptical (that is our job), but to imply that those who deny climate change are somehow ahead of their time is wholly misleading. The greats who did so in the past put forward evidence that broke the consensus of the time and moved the science forward. Those who continue to deny climate change muddy the waters of action and delay the urgent measures we so desperately need. If Lord Leach still feels challenged by the science I suggest he reads some accessible blogs on climate change, such as www.celsias.com or www.realclimate.org. Once he has got up to speed on the science, Lord Leach might wake up to the considerable problems we face and make a more valuable contribution to the public debate: how to get ourselves out of the mess we’ve created.

Professor Chris Turney

University of Exeter

Sir, In the world inhabited by Lord Leach, that of making money, momentous decisions are taken daily on virtually no scientific evidence. In contrast, caution is the constant companion of scientists when drawing conclusions from the evidence they have accumulated. This caution is very evident in the recent IPCC report, in which all conclusions are expressed in terms of probabilities.

Far from being a new idea, the concept of greenhouse gases was described by Fourier in 1824 and the role of carbon dioxide and other compound gases in trapping the Sun’s radiation by Tyndall in 1860. For many decades this was simply regarded as an explanation of why life was able to develop on our planet and thought to be beneficial in terms of encouraging agriculture. But an exponential rise in carbon dioxide has been recorded since the early 1960s and ice-core atmospheric samples have now shown current concentrations to be almost double the highest found in the previous 400,000 years. There is currently a very serious imbalance between production of greenhouse gases and their removal by the oceans and vegetation.

No amount of special pleading by those whose livelihood depends on ever-increasing use of the Earth’s unrenewable resources can alter the facts that greenhouse gases are rising and that the effect of such a rise is to trap more of the Sun’s radiation in our planet. It is very unwise to attempt to persuade the scientifically unsophisticated that they need not worry.

Professor Anthony Seaton

Edinburgh

Sir, Perhaps taxpayers’ money would be better spent on tackling not the linear increase in CO2 emissions but the exponential increase in the world population.

Robert Freer

London SE21

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