A few days ago I interviewed the prominent climate change sceptic Professor Ian Plimer for a piece ahead of the UN climate negotiations in Copenhagen. Very little of our half-hour conversation made it into the final story but it was a revealing interview. This blog is an attempt to put some of what we talked about on the record.

It is important to do so, because the Australian mining geologist's book Heaven and Earth – on what he calls the "missing science" of global warming – has proved extremely popular. It has been reprinted six times in the UK since its publication in March and has sold more than 30,000 copies in Australia. In July, the Spectator ran a fawning cover feature about the book under the headline "Relax: global warming is all a myth".

The new Australian opposition leader, Tony Abbott, was converted to the sceptic cause by reading the book, or so Plimer says. And the backbench Tory MP Douglas Carswell said it overturned his belief that climate change is a human-caused phenomenon.

But it has also come in for stinging criticism from scientists and others. Bob Ward, director of public relations and policy at Lord Nicholas Stern's Grantham Institute at the London School of Economics said the book is "full of inaccurate statements and misrepresentations of global temperature data".

Plimer has refused to answer a series of questions put by George Monbiot about specific claims he makes in the book, but our interview gave me the opportunity to put some of those - and others' questions - to him.

I found him to be one of the most difficult and evasive interviewees I have spoken to in my career, frequently veering off on tangents rather than answering the question I had put.

Strangely, Plimer was only vaguely aware of the criticisms that have been levelled at Heaven and Earth and appeared to have little interest in dealing with them. He gave me the impression that engaging with his critics was beneath him. That seemed to me an odd attitude for a scientist to take. He did say though that when he returned home from promoting the book he planned to write a less technical follow-up to Heaven and Earth that would address some of the criticisms.

The first figure in Heaven and Earth makes a bold claim:

This diagram shows that the hypothesis that human emissions of CO2 create global warming is invalid.

It is a graph running from 1990 to 2025 and shows five different plots of global temperature. One of these plots is the so-called HadCRUT temperature series produced by the Met Office's Hadley Centre and Climatic Research Unit at the University of East Anglia.

Plimer's first mistake is to refer to this plot as a "computer prediction" of temperature when this is in fact the measured global average temperature. But more significantly, the final point on his graph is a long way from where it should be. The figure for 2008 is placed much lower than the correct figure (at 0.1C above the 1961-1990 average instead of 0.437). That might not sound like much, but it wrongly gives the impression there has been a massive recent cooling – something Plimer says the climate modellers have not predicted.

His broader point appears to be that if climate models cannot predict warming over the course of a decade, what hope do they have of getting the forecast right for 2050 and beyond? Leaving aside the misplaced data point, Plimer appears to have misunderstood what climate models can and can't do. It may seem paradoxical, but predicting the year-by-year fluctuations in global temperature is actually a lot harder than predicting the general trend. No one who understands climate modelling would expect a perfect fit on such a short timescale.

"His premise that the models do not represent the [real data] is flawed," said a spokesperson for the Met Office. "The models never claim to predict the individual variability from year to year. However, they do clearly show the trend over longer periods of time."

Elsewhere in the book, Plimer appears to have conflated a US temperature record and the global average temperature. On page 99 he writes "Nasa now states that […] the warmest year was 1934." The Nasa dataset he is referring to covers the US only but he seems to be referring to the world average.

Again, Plimer does not appear to accept that the world is warming. But in fact, the hottest year on record is 1998 and eight of the 10 hottest years ever recorded have occurred this century.

When I put the mistake to him he responded: "The 1930s in North America and probably the rest of the world were a hot period of time." But what about increased global average temperature since then? "That has been disputed by many of my colleagues who I have a great regard for because they've been the people involved in putting measurements together ... I do dispute that as do many other people who are far more qualified in atmospheric sciences than I."

He appears to be taking the bizarre position that the world has not warmed since the 1930s. Even global warming critic Lord Nigel Lawson doesn't say silly things like that.

Now Plimer is not a climate scientist so you can perhaps forgive his glaring errors when writing about that field, but one thing he might hope to get right would be his own field of geology. Sadly not.

On page 413 of the book he repeats the old canard that "Volcanoes produce more CO2 than the world's cars and industries combined". It was a claim that he famously made in a recent interview by Justin Webb on the BBC's Today programme. Webb did not challenge him, but I put it to Plimer that the website of the US Geological Survey (USGS) states: "Human activities release more than 130 times the amount of CO2 emitted by volcanoes."

Plimer's response was that the USGS is only talking about terrestrial volcanoes and has not incorporated CO2 produced by undersea eruptions at mid-ocean ridges. "85% of the world's volcanoes we neither see nor measure," he said. "They leak out huge amounts of carbon dioxide... That does not come into the USGS figures nor does it come into the Intergovernmental Panel on Climate Change's figures."

If he is right, that is an astonishing omission and an oversight that would force a huge reassessment of climate science.

But when I check with the USGS they are very explicit. According to volcanologist Dr Terrence Gerlach:

I can confirm to you that the "130 times" figure on the USGS website is an estimate that includes all volcanoes – submarine as well as subaerial ... Geoscientists have two methods for estimating the CO2 output of the mid-oceanic ridges. There were estimates for the CO2 output of the mid-oceanic ridges before there were estimates for the global output of subaerial volcanoes.

These are just three of the many criticisms that have been made about Heaven and Earth. Plimer dismissed them as "pathetic nit-picking" but if his book is influencing politicians and public opinion around the world then I think his arguments deserve close scrutiny.

He likes to argue that his position on global warming is dismissed by mainstream scientists because they are part of a "fundamentalist religion" and a "mafia". In fact, his arguments are rejected because they are just plain wrong.