Plimer vs Plimer: a one man contradiction

On 30 October, Ian Plimer wrote to The Weekend Australian, lamenting that noone had explained to him how anyone could be concerned about carbon dioxide given that most of its sources were supposedly natural. However, a thorough explanation of how we know humans are causing the increase in CO2 levels can be found on pages 414 and 415 of a 2009 book on climate change. The book is called Heaven and Earth. The author, Ian Plimer.

Plimer contradicting Plimer is not an isolated incident. One of his pet arguments is that carbon dioxide has been much higher in the past, without the Earth going into meltdown. He concludes that carbon dioxide can't have much of a warming effect. There's a major flaw in this line of thinking. The further back in time you go, the cooler the sun gets. If it wasn't for the warming effect of carbon dioxide, the Earth would've been a frozen iceball throughout much of its history.

The question that has long burned in my mind was how could Plimer, a geologist, not know that the sun has been steadily warming throughout Earth's history. A proper understanding of greenhouse warming over geological timeframes requires considering both CO2 levels and solar activity. You would expect this kind of over-simplified misinformation from a blogger sourcing their information from other blogs but from a professional geologist? Well, at this point, the mystery deepens.

It turns out Plimer is aware that the sun has been steadily warming over the Earth's history. In his 2001 book A Short History of Planet Earth, Plimer explains how the warming effect from CO2 kept our planet from freezing into an ice age when the sun was cooler (emphasis mine):

The early Sun had a luminosity of some 30 per cent less than now and, over time, luminosity has increased in a steady state. The low luminosity of the early Sun was such that the Earth's average surface temperature would have been below 0°C from 4500 to 2000 million years ago. But, there is evidence of running water and oceans as far back as 3800 million years ago. This paradox is solved if the Earth had an enhanced greenhouse with an atmosphere of a lot of carbon dioxide and methane.

If you're confused at this point, you're not alone! Which Plimer are we to believe? The Plimer who considers the full body of evidence and comes to conclusions consistent with the scientific consensus that increased greenhouse gases causes warming? Or the Plimer who cherry picks the data, withholds vital pieces of evidence and misleads the public. I know which I prefer.

Perhaps Plimer had a change of heart between 2001 to 2009? After all, a bloke is allowed to change his mind (although changing your mind in this case means going from considering all the evidence to ignoring any inconvenient evidence). But no, such a kind interpretation is not possible with Plimer. When you flick through his 2009 book 'Heaven and Earth', self-contradictions abound.

On page 121, Plimer tells us that in the Earth's past, a rise in CO2 caused a 4 degree temperature rise. But on page 165, we're told CO2 doesn't drive climate. 21 pages later, the warm temperatures of the Cretaceous period are attributed to elevated CO2 levels. But flip forward to page 278 where he tells us that temperature and CO2 are not connected. If you're the type of person who likes to jump to the end of the book, you'll find on page 411 that CO2 keeps our planet warm.

And that's just on the topic of the warming effect of CO2. The contradictions cover a range of issues. We're told that El Nino lasts for a month or so, then 2 pages later, it lasts for 1 to 2 years. We are informed that 650,000 years ago, CO2 levels fell as low as 185 parts per million (we're currently at 390 parts per million). And yet later in the book, Plimer claims that CO2 has never been as low as current values in thousands of millions of years.

And returning to the subject of rising CO2 levels, Plimer provides several pages of quality exposition on the different types of carbon atom (called isotopes), explaining the multiple lines of evidence indicating that humans are responsible for the rise in CO2. Yet a few pages earlier, he'd stated that volcanoes produce more CO2 than humanity. If you want to read a good debunking of the "volcanoes are responsible for the rise in CO2" myth, flip to pages 414 and 415, where the man who said it mercilessly shreds himself to pieces.

Is Plimer the climate version of Harvey Dent (aka Two Face from Batman), flipping a coin to decide which side of the science to present? Or perhaps enlightenment comes from the saying, "the best lies are always at least partially true". Embedding weeds in amongst the truth is unfortunately an effective strategy, making it difficult to distinguish between the two. 

So how does the average layperson, lacking the time to dig through peer-reviewed references, tell the difference between accurate science and misinformation? A useful resource is the 64 page critique by Professor Ian Enting from the University of Melbourne. Enting provides a comprehensive, point-by-point examination of Plimer's book, exposing the inconsistencies and misrepresentations.

Or for those who lack the time (or attention span) to pore through Professor Enting's thorough document, I've created a more visually stimulating resource - a two column comparison of quotes where Plimer contradicts himself. The resource is titled, appropriately, Plimer vs Plimer. It's by no means comprehensive as it only includes content from two of Plimer's books - I have yet to include any of his articles, interviews or lectures. But it presents a clear picture of the internal inconsistency of Ian Plimer: a one man contradiction.

To refer people to this resource, the short URL is or if that's not short enough, you can also use (and if that's not short enough, then tough, that's as far as I'm going). 

Posted by John Cook on Friday, 9 December, 2011

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