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Professor Ian Plimer, author of the book Heaven and Earth, is the new champion of the climate change deniers. After I wrote an article attacking his claims, he challenged me to a public debate. Last week I told him that I would accept his challenge as long as he accepted 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. Plimer rejected my challenge.

I wrote an article accusing him of cowardice. I sent him the URL in the hope that it would provoke him into changing his mind. It worked. He wrote back, suggesting that he would now answer my questions. So here's the letter I've just sent him. If Plimer answers them and accepts my condition that we can cross-examine each other, we will move on to his challenge - a face-to-face debate. Let battle commence!

Dear Ian,

I am delighted to hear that you have reconsidered your position, and that you are now prepared to engage with me in writing. Here are my questions. Please answer without resort to bluff or bluster. I am looking for precise and specific responses, with references attached.

There are dozens of grave concerns raised by scientists about alleged false claims, misrepresentations and distortions in your book Heaven and Earth. Were I to try to represent them all, this post would run to many pages. So I have chosen just a few. The criteria I have used are as follows:

- These statements are either right or wrong, sourced or unsourced.

- They are critical to your argument. If they turn out to be false, they torpedo your thesis.

- If your claims are correct, you should be able to answer my questions briefly and easily.

For a fuller list of the alleged falsehoods and distortions your book contains, please see the critiques by

Tim Lambert, Ian Enting, Barry Brook, Michael Ashley, David Karoly and Kurt Lambeck.

Once you have given clear and precise answers to these questions, we can confirm the date of our face-to-face debate.

1. The first graph in your book (Figure 1, page 11) shows global temperatures, as measured by the Hadley Centre (HadCRUT), falling by 0.3C between 2007 and 2008. In reality the fall recorded by the HadCRUT3 data series is 0.089C.

How do you explain the discrepancy between the HadCRUT3 figure and your claim?

2. Figure 3 (page 25) is a graph purporting to show that most of the warming in the 20th Century took place before 1945, and was followed by a period of sharp cooling. You cite no source for it, but it closely resembles the global temperature graph in the first edition of Martin Durkin's film The Great Global Warming Swindle. Durkin later changed the graph after it was shown to have been distorted by extending the timeline.

In your book it remains unchanged.

Tim Lambert has reproduced the graph here.

a. What is the source for the graph you used?

b. Where was it first published?

c. Whose figures does it use?

d. How do you explain the alteration of both the curves and the timeline?

3. You maintain that:



"the last two years of global cooling have erased nearly thirty years of temperature increase."

(page 25)

Again you do not provide a reference. As you can see here, the Met Office HadCRUT3 series shows that this claim is untrue.

a. Please give the source for your claim.

b. How do you reconcile it with the published data?

4. In your discussion of global temperature trends, you maintain that:

"NASA now states that […] the warmest year was 1934." (p99)

a. Are you aware that this applies only to the United States?

b. Was this a mistake or did you deliberately confuse these two datasets?

5. Discussing climate trends in the Arctic, you state that:

"the sea ice has expanded" (p198).

Again, you give no reference.

a. Please give a source for this claim.

b. How do you explain the discrepancy between this claim and the published data?

6. You state that:

"If the current atmospheric CO2 content of 380 ppmv were doubled to 760 ppmv […] [a]n increase of 0.5C is likely" (p366).

Again you give no source. Please provide a reference for this claim.

7. You claim that:

"About 98% of the greenhouse effect in the atmosphere is due to water vapour." (p370).

Ian Enting says:

"In some cases the numbers given by Plimer are exaggerated to such an extent as to imply that without water vapour, Earth's temperature would be below absolute zero - a physical impossibility."

He explains this as follows.

You state:

"The Earth has an average surface temperature of about 15C […] If the atmosphere had no CO2, far more heat would be lost from Earth and the average surface temperature would be -3C." (p366)

Enting says:

"The implication of attributing 18C of warming to CO2 while saying […] 'About 98% of the greenhouse effect in the atmosphere is due to water vapour' is to imply that in the absence of CO2 and H2O, the temperature would be 900C lower, i.e. well below the physical limit of absolute zero."

Again you give no source.

a. Please provide a reference for your claim about water vapour.

b. Please explain how your two statements (98% of the greenhouse effect is caused by water vapour and 18C can be attributed to CO2) can both be true.

8. You cite a paper by Charles F Keller as the source of your claim that:

"satellites and radiosondes show that there is no global warming." (p382)

This is what the paper 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 center pole that held up the critics' entire "tent." Their argument was that, if there had been little warming in the past 25 years or so, then what warming was observed would have been within the range of natural variations with solar forcing as the major player. Further, the models would have been shown to be unreliable since they were predicting warming that was not happening. But now both satellite and in-situ radiosonde observations have been shown to corroborate both the surface observations of warming and the model predictions."

a. How did you manage to reverse the findings of this paper?

b. Was it a mistake or was it deliberate misrepresentation?

9. You state:

"The Hadley Centre in the UK has shown that warming stopped in 1998" (p391).

Again you produce no reference.

This is what the Hadley Centre says:

"The evidence is clear – the long-term trend is that global temperatures are rising, and humans are largely responsible for this rise. Global warming does not mean that each year will be warmer than the last. Natural phenomena will mean that some years will be much warmer and others cooler. You only need to look at 1998 to see a record-breaking warm year caused by a very strong El Niño. In the last couple of years, the underlying warming is partially masked caused by a strong La Niña. Despite this, 11 of the last 13 years were the warmest ever recorded. […] Over the last ten years, global temperatures have warmed more slowly than the long-term trend. But this does not mean that global warming has slowed down or even stopped. It is entirely consistent with our understanding of natural fluctuations of the climate within a trend of continued long-term warming."

a. Please give a reference for your claim.

b. How do you explain the discrepancy between your account of what the Hadley Centre says and theirs?

10. You state that:

"Volcanoes produce more CO2 than the world's cars and industries combined." (p413)

This is similar to the claim in The Great Global Warming Swindle, whose narrator maintained that:

"Volcanoes produce more CO2 each year than all the factories and cars and planes and other sources of man-made carbon dioxide put together."

But you do not provide a source for it.

This is what the US Geological Survey says:

"Human activities release more than 130 times the amount of CO2 emitted by volcanoes".

a. Please provide a reference for your claim.

b. How do you explain the discrepancy between this claim and the published data?

11. You maintain that:

"termite methane emissions are 20 times potent than human CO2 emissions". (p472)

Please provide a source for this claim.

Thank you,

Yours Sincerely,

George Monbiot