So at last we've had our fight, and Ian Plimer has cause to regret his challenge to me. Back in July, Plimer, an Australian professor of geology and a climate change denier championed by the right wing media all over the world, challenged me to a debate in London, to be hosted by the Spectator magazine. I agreed, as long as he met a simple condition: to answer a list of questions about the claims in his book, Heaven and Earth. Plimer eventually accepted this condition. My questions were straightforward: I asked him only to explain or reference the claims he made. Any reputable scientist would have answered them without hesitation.

But Plimer used a series of excuses and evasions to put me off.

Eventually I gave him a deadline. Four days before it expired, the Spectator cancelled the debate, and gave Plimer a platform to himself. It was a shocking episode, which suggested to me that neither Plimer nor the Spectator wanted to face the facts.

Anyway, the Australian television network ABC renewed the invitation. Knowing that Plimer might use any conditions as an excuse for wriggling out again, this time I agreed without terms. The debate, which was hosted by Tony Jones, took place live on ABC's Lateline last night. You can watch it here.

It began with a general discussion about Copenhagen, climate denial and, of course, the hacked emails. Plimer described the contents of the Climatic Research Unit's emails as "the biggest scientific fraud in history".

I replied that, though I deplore some of the behaviour revealed by the emails, Plimer's own behaviour is highly questionable. He continues to restate facts after they have been shown to be wrong. For example, he maintains that volcanoes produce more carbon dioxide than human activity. The US Geological Survey (USGS) reports that human beings produce 130 times as much CO2 as volcanoes.

Jones took up my charge and asked Plimer whether he stood by his claim that volcanoes produce more CO2 than all the world's cars and industries.

Plimer replied "I'm very heartened that a journalist is correcting me on my geology", then launched into a disquisition on how I know nothing about science. Both of us pressed him to answer the question. So Plimer said that neither of us had read his book. We both replied that we had and pressed him again.

Plimer tried to argue that the US Geological Survey only measured emissions from terrestrial volcanoes – not from submarine volcanoes. Jones, who had plainly done his homework, pointed out that a UK journalist (I think he was referring to the Guardian's James Randerson) had gone back to the USGS and asked them whether or not submarine volcanoes were included in its calculations. They were.

Plimer went off at a tangent, starting to list the numbers and kinds of submarine volcanoes. This, I soon found, was a characteristic tactic: when faced with a tricky situation, he starts throwing out random facts. I pointed out that he had been told many times that the USGS figures include submarine volcanoes: he was making a claim on national television that he should know is wrong.

Jones raised another of the questions I had tried to put to Plimer: the professor has stated that the Met Office's Hadley Centre has shown that warming stopped in 1998. Where, Jones asked, does the Hadley Centre say that? Again the random facts came thick and fast.

Plimer said there are four major centres that measure temperature. Some of them use thermometers (would you believe it?); some use radiosondes; some use satellites. And if you look at page 481 of my book, you'll find that I nailed the University of East Anglia, which is actually just a few yards down the road from where Monbiot lives, and, and …

It was a weird form of free association, which might have contained answers to any number of questions – but not the one he was asked. I pointed out that he had cherry-picked his start date: his claim that temperatures had fallen this century was based on his selection of the hottest year ever – 1998 – as the starting point. Had he picked 1997 or 1999, or any other year in the 20th century, he would have seen that temperatures had risen.

Tony Jones asked Plimer to respond. His answer ranged from the correspondence we had had, to my absence of qualifications, to Roman warming, medieval warming, to the Met Office saying the UK would have a barbeque summer this year, to the temperature 4,000 years ago – in fact any temperature series except the one he was asked about.

Whenever I pressed him to answer the question, Plimer said it was "the height of bad manners" to interrupt him. When Jones pushed him again, he started talking about wheat farming in Greenland and grapes in Roman Britain. In my quarter century as a journalist I have never seen anyone go to such lengths to avoid answering a simple point.

Jones asked Plimer about another of his howlers: he had exactly reversed the findings of a paper he cited. In his book, he claims that "satellites and radiosondes show that there is no global warming", and gave as his reference a paper by Charles F Keller. Here's what the paper actually says:

"The big news [is] the collapse of the climate critics' last real bastion, namely that satellites and radiosondes show no significant warming in the past quarter century. Figuratively speaking, this was the centre pole that held up the critics' entire 'tent'. … But now both satellite and in-situ radiosonde observations have been shown to corroborate both the surface observations of warming and the model predictions."

Off Plimer went with another series of random facts, about corrections of satellite data, different datasets: anything but address his reversal of the findings of the paper he referenced. Yet again I pointed out that he was evading this question, and this time he veered off on to a completely different subject: the websites I read and who is funding them. He didn't explain what this had to do with his misrepresentation of the satellite paper.

I finished by pointing out that throughout the discussion Plimer had used evasion and distraction when faced with straight questions. As soon as the interview ended, the emails started pouring in. Scores of them. The overwhelming message was that Plimer had been soundly thrashed. You can judge for yourself. If you bought his book or read the articles about him and you believed what he said, watch the interview, then tell me you still stand by him.

monbiot.com