Is Professor Ian Plimer a chicken? After I attacked some of the crazy claims he made in his book Heaven and Earth, the good professor challenged me to a face-to-face debate. At first I wasn't interested: judging from his responses to his critics, he appears to be impervious to reason. I can picture him standing up to his neck in water, still telling us not to worry about global warming — it's all been dreamed up by a global conspiracy.

More importantly, it seems to me that he's a grandstander, who wants nothing more than to make as much noise as possible in the hope that it will drown out the precise refutations published by his book's reviewers. As far as I can discover, he has yet to produce any specific response to the very serious allegations they have made, preferring to heap insults on them instead. To resolve these issues, we need to establish the facts and provide references. This is why I want him to answer them in writing; ideally in electronic format, so that people can follow the links. I was concerned that a face-to-face debate, with all its bluster and generalisations, would let him off the hook.

But then it struck me that there was no reason why we couldn't do both. Last week I wrote to Professor Plimer accepting his challenge, on the condition that he accepts mine. I would take part in a face-to-face debate with him as long as he agreed to write precise and specific responses to his critics' points — in the form of numbered questions that I would send him — for publication on the Guardian's website. I also proposed that there should be an opportunity at the debate for us to cross-examine each other.

This morning I received a message from Professor Plimer, rejecting my challenge. So much for his enthusiasm for debate.

In case he has somehow missed the point of my conditions, I have spelt them out again. In a face-to-face debate, any specific claims he makes will be impossible for the audience to check during the event. In a written exchange, readers can see for themselves whether or not his specific claims stack up. The two debates are complementary: having had the opportunity to check his specifics, people at the face-to-face debate can better assess his generalisations.

There is no good reason that I can think of why he would wish to avoid this process: in fact it gives him an excellent opportunity to answer the very damaging allegations made by his critics. There is an obvious bad reason: he has no answers to their points.

Cross-examination allows us to put each other's claims to the test and ensures the other person can't avoid the question.

Will Professor Plimer accept my challenge, or are we to conclude that he can't face the music? Does all this posturing as the brave maverick exposing a global conspiracy really conceal a broad yellow streak?

Monbiot.com