Tory peer accused of using 'meaningless' comparisons to try to make his argument against the need to tackle global warming

Lord Lawson, the former chancellor, has been privately accused by the government's chief scientific adviser of making "incorrect" and "misleading" claims in his book on climate change.

The charge against Lawson, the country's most prominent global-warming sceptic, was made during an extraordinary and at times fractious exchange of letters between the men following a meeting over coffee at the Lords.

Sir John Beddington wrote to Lawson to tell him that his book, An Appeal to Reason: A Cool Look at Global Warming, had made "a number of points related to the underlying science of climate change that are incorrect or presented in a misleading way". An appendix to his letter accused Lawson of making "meaningless" comparisons to prove his thesis.

In response, Lawson wrote back to accuse Beddington of attempting to "trump" his arguments without evidence or quantification. He also confessed to being baffled by Beddington's criticisms, adding that the government adviser had committed a "gross misuse of language" in claiming that the Earth has warmed "dramatically" in the past 150 years.

Lawson, who is chairman of the sceptical Global Warming Policy Foundation, is the most prominent critic of the government's policies on climate change. While not denying that there is evidence of a change in the climate, he has announced himself unconvinced that it has been caused by greenhouse gases.

Lawson is set to represent the climate sceptics at a debate hosted by the Spectator magazine, entitled "The Global Warming Hysteria Is Over: Time for a Return to Sanity".

But Christian Hunt of the website Carbon Brief, who, along with investigations website Spinwatch, uncovered the letters, said they showed Lawson did not have a grasp of the science: "It is worrying that a prominent figure like Lord Lawson is seen as a credible commentator on this issue, when his understanding of appears so flawed."

"His climate-sceptic thinktank, the Global Warming Policy Foundation claims a charitable aim 'to advance the public understanding of global warming', but they seem to spend most of their time casting doubt upon well-established science."

Speaking from his home in Gascony, Lawson denied to the Observer that he had been "upset" by Beddington's criticisms and said he had failed to find a single factual inaccuracy in his book, which was first published in 2008. "We got on well in personal terms, but it wasn't a meeting of minds," he said."I wasn't upset in the slightest, because I seem to recall that I thought that he had missed the point. "I am chiefly concerned with what is a sensible policy. I seem to recall that none of the things in that appendix really affected the question of what policy one should pursue. Moreover, so far as my book is concerned, he was … unable to find a single thing in it that was factually inaccurate."

Of his first meeting with Beddington, before their correspondence began, Lawson added: "He had been recently appointed and he seemed to me to be a reasonably sensible fellow, and I said come along and have a cup of coffee at the Lords and discuss this together."

Beddington's first letter to Lawson was written a month after their meeting last March. To Lawson's claim in his book that there has been no "further global warming since the turn of the century", Beddington wrote: "Short-term temperature trends are meaningless in the context of global warming."

To Lawson's claim that calculating average global temperature is not straightforward and data from the developing world and former Soviet Union were not reliable, Beddington claimed those issues were taken into account and warming could be seen in other ways, such as in the decrease of Arctic sea ice.

To Lawson's claims that urbanisation raises near-surface temperatures and might be responsible for the recording of global temperature rises, Beddington said it has been studied and found to have a "negligible effect".

And to Lawson's claim that "neither scientists nor politicians serve either the truth or the people by pretending to know more than they do", Beddington wrote: "It is clear from the scientific evidence … that the risks are real and, I believe, it is not going too far to say, potentially catastrophic in the absence of strong global action to reduce emissions."

A month later Lawson wrote back thanking him for his "very full response". But he warned Beddington, as a scientist, against the "journalistic" phrase "catastrophic climate change". He then described his use of statistics as arbitrary, and his facts as carefully selected.

A month later, Lawson again wrote to Beddington demanding that he write to the Guardian to deny a report that the civil servant had been highly critical of the Global Warming Policy Foundation. Beddington refused, claiming he had not criticised Lawson and stood by his criticisms about those who rely on anecdotal evidence to disprove climate change.