An explanation of the “percentigrade” error which even John Gibbons should be able to understand

Or, taking a sledgehammer to crack a nut – apologies for overkill

but weaning Mr Gibbons from some of the tenets of his faith must be much like driving a stake through the heart of a vampire – I don’t think I have met anyone who can truthfully claim to have succeeded in either endeavour.

This is a pity, as when Mr Gibbons is not looking at the world through alarmist glasses he can write quite sensibly. He thinks for himself and parts company with many of his fellow activists and environmentalists on nuclear power, on vaccination, on homoeopathy, if my memory has not failed me, and other issues which would require a trawl through past columns and blog posts.

For anyone unaware of John Gibbons’ stubborn insistence on displaying his lack of understanding of elementary science concepts, he provides a good introduction here himself:

Comment and reply at

Again, for anyone not familiar with John Gibbons’ style, the air of authority, the sneering and condescension [just in case John’s own fanboys may need a little help here: “Just in case you’re not familiar with the basic science (and I really am now beginning to wonder)”] are helpfully displayed. From the regular repertoire, just missing is the suggestion that the commenter is suffering from a Dunning-Kruger effect, as in the following response to another comment:

Here’s a very helpful article on the Dunning-Kruger effect, entitled ‘When Ignorance Begets Confidence’. It explains the “double curse” that people who are incompetent at reasoning suffer from being unable to recognise this incompetence. Hence creationism, conspiracy theories, climate denialism, anti-vaccination campaigners, etc.

As for “a slight lack of precision in a blog posting from three and a half years ago”, it was not just a single blog posting three and a half years ago. But more on that further below.

And as for the support of his physicist – if sober (the physicist that is, not me) I can only charitably speculate that he must have assumed that someone who has styled himself “a specialist environment writer” could only be taking the piss when asking such a silly question, and replied in like vein. John might well ponder why none of his fanboys, friends and colleagues have stepped in to gently tell him not to make a fool of himself in this way. At a minimum, at least one of the named contributors listed on his blog must certainly know that this is not “an entirely reasonable approach” but rather complete nonsense.

John clearly does not understand why his percentage calculation is nonsense rather that that “entirely reasonable approach”. It is very simple really John. Most people understand that you can talk about percentage increases in rainfall for example. There is a real zero. 0 mm, 0 inches, 0 cubits, 0 feet – they all mean the same thing, no rain. But 0° Celsius and 0° Fahrenheit do not mean the same thing, and certainly not no “temperature” or heat. So for slow learners let us reframe the calculation in a business setting since John is a businessman, not a scientist. And since alarmists seem to like to write parables or fables about a dystopian future, let’s follow suit.

John is seeking an investor for a project he has in mind. A modest investment of €10,000 is required. His accountant suggests that an investor may expect a return of €140, or 1.4%. John however feels that an entirely reasonable approach would be to calculate the percentage return by dividing this return of €140 by the excess investment over €9492.50, or €507.50, giving a return of over 25%. This is, after all, “an entirely reasonable approach”, exactly equivalent to dividing an increase of 4°C by 14.5°C, which is just the excess over 0°C, the arbitrary zero point of the Celsius temperature scale, rather than by the excess over zero Kelvin, which would be the equivalent calculation to the nit-picking one which his accountant had carried out.

On returning to his accountant to complain about this nit-pickery, the accountant tries to dissuade John, suggesting that he should consider the result of a “Fahrenheit” style alternative to his “Celsius” style calculation. Daniel Fahrenheit had set the zero point of his scale at the point at which he could freeze brine rather than water, so leaving the arbitrary Celsius zero point at 32°F. The Fahrenheit equivalent of John’s 4°C is 7.2°F, and 14.5°C is 58.1°F. We now have a percentage increase of only 12.4%, as would be obtained in the exactly equivalent investment calculation by dividing the return of €140 by the excess investment over €8870.28, or €1129.72, rather than the excess over zero Rankine (the absolute zero based equivalent of Kelvin for Fahrenheit users).

John’s accountant pleads in vain that proper accounting calls for calculation of a return or percentage increase by dividing by an absolute, zero based, amount, not by an excess over some arbitrarily chosen datum. He even points out that were John dealing with temperature it would make absolutely no sense if the resulting percentage increase for an identical increase in temperature, say 4°C or 7.2°F, over an identical starting temperature, say 14.5°C or 58.1°F, were to depend on the choice of temperature scale, Celsius or Fahrenheit. It is exactly the same physical reality which is being observed.

John however is adamant. None of his many learned friends, some of them even climate scientists and physicists he points out, who must know more about temperature than any accountant, have ever suggested that his approach is anything other than “entirely reasonable”. As we know, there is an old saying that “there’s one born every minute”, and John finds his investor.

How this fable ends when the matter comes before the Commercial Court is left as an exercise for the imagination of the reader.

Moving from this facetious tone to more serious matters

“Trying to calculate it against zero Kelvin”, contrary to John’s confident assertion, is neither “completely idiotic” nor “obscurist” (obscurantist may the word John is thinking of, to indulge in a little nit-picking which is not unknown from John himself. It is simply the only correct way to carry out the calculation that John wished to carry out. The result may not provide much enlightenment, but at least it is not the utter, and so misleading, nonsense that John has written. He appears not to notice that the correct percentage increase of 1.4% was presented to him not as a meaningful value in its own right but rather as a correction to his nonsense. He may well be able to find an obscure blog somewhere “on the other side” presenting such a value if he is willing to spend enough time searching, but it is interesting to note that I have never seen anyone else on “John’s side” perform John’s calculation on temperatures – I have indeed seen it elsewhere than on John’s blog or in his column in the Irish Times, but on each occasion it turned out to be a reposted article by John.

You may note that while John refers to “a slight lack of precision in a blog posting from three and a half years ago”, he was making this “calculation” in different forms over a more extended period. I first noticed it five years ago in a column in the Irish Times:

First, the science bit. Global average temperatures have increased by 0.8 degrees since industrialisation began. This translates to a world that has become 6.5 per cent warmer.

And as the commenter above pointed out in relation to the first quotation above, he has removed this, and any other post with a similar blunder, from his blog. Why he felt the need to remove such posts is a question worth asking.

This Irish Times article can still be found at (this may be paywalled), at, and, least these two should be removed or amended, also at

Somewhat disturbing that this article has graced the ICARUS website for some five years now, with no comment regarding the scientific nonsense represented by John’s percentage. As a past webmaster for an academic department I would certainly have expected to be asked to explain had I failed to add a warning note to flag such nonsense in any material I posted, or which was posted by others. Can it possibly be that not a single person at ICARUS noticed this over five years?

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