Last month there was a fifty minute debate between a climate sceptic and a defender of the official position on the French radio channel France Culture. The website advertised it as follows:
“How can one be a climate sceptic today? Are the problems epistemological, philosophical, or political? Is the uncertainty in climate theory ignorance? A duel between Jean-Pierre Dupuy and Benoît Rittaud.”

And duel it was. According to Benoît in his post-match report on the Climato-sceptique blog the “enlightened catastrophist”, philosopher Jean-Pierre Dupuy was so unpleasant during the interval that the programme’s presenter Adèle Van Reeth threatened to have him thrown out of the studio. Adèle is to be congratulated for her patience and her apparently genuine desire to explore the subject fairly and thoroughly.

Here’s my transcription/translation. I offer it, not as a document that will enlighten you about the theory of global warming, but as a little masterpiece of the Theatre of the Absurd.

Adèle Van Reeth: What are the climate sceptics sceptical about? The imminence of the predicted catastrophe? The responsibility of man for global warming? The existence even of climate change? Our capacity to counter a development considered as dangerous? And above all, what motivates them? Common sense or insolence? […]
We’re ending our series this week with an examination of the relevance of scepticism today, based on the scientific and philosophical arguments.
So if you find it difficult to take climate sceptics seriously, if you think its scandalous to minimise the importance of the dangers facing us, Jean Pierre Dupuy will present his arguments. Bonjour Jean Pierre
Jean Pierre Dupuy: Bonjour
AVR: If on the other hand the consensus on the responsibility of humanity in the evolution of the climate weighs on you, if you doubt the validity of the opinions of those who issue dire warnings, Benoît Rittaud will appeal to you, Bonjour Benoît
Benoît Rittaud: Bonjour
AVR: Jean Paul Dupuy, you became a philosopher after studies at the Polytechnique and the Cours des Mines. You are author of “For an Enlightened Catastrophism” and “A Brief Metaphysics of the Tsunami”, while you, Benoît, are a mathematician, lecturer at the University of Paris 13, author of “The Climate Myth” and “The Exponential Fear”.
Voice 1: [from “the Manila Appeal”, by Marion Cotillard] Considering that we are reaching the point of no return in the case of climate change, and that we have to pass from the stage of intentions to that of action, we call solemnly on all states to work practically and rapidly to counter climate change, and in particular against its impacts, and we invite them to present their contributions at the national level in function of their respective national situations and capacities
Voice 2: [from: François Poullain de La Barre: “On the Equality of the Two Sexes, a Physical and Moral Discourse in which We see the Importance of Ridding Oneself of Prejudices” 1673]
The idea of reality being attached naturally to that of science, man tends to assume as true that which is proposed by those who have the reputation of being wise. And as the number of those who have only the reputation of so being is much larger than that of those who are so in fact, the average man, who simply counts the number of opinions, cleaves to the former group, and the more willingly embraces their opinion, given that it corresponds more closely to that which he holds already. In the case of poets and orators, who have no other aim than to please and persuade, the appearance of truth is sufficient for most people. Thus, as exaggeration and hyperbole serve well their purpose, by exaggerating their ideas at will, they cause things to appear good or bad, big or small, as they please. The style with which they ornament their discourse contributes marvellously to create the belief of those who are not on their guard. They speak with facility and grace, using certain manners of expression which are attractive, agreeable and uncommon to dazzle the mind and prevent it from perceiving the truth.
AVR: It may seem strange to start a programme on climate scepticism with a quote from François Poullain de la Barre – an extract from his work “The Equality of the Two Sexes”. However, Benoît, it’s a suggestion which we accepted gladly, because it’s true that the argument used in this text will prove useful for this debate. Explain to us why.
BR: In the climate debate, one of the main arguments put forward is that of the consensus, which is not at all a scientific argument, obviously, because science doesn’t proceed by consensus. It’s essentially a political argument, and it’s interesting to see that, when one looks at the history of science, or more generally the history of ideas, that the consensus, while it’s not always mistaken, is often wrong, and the one here which is not well known, is the idea of Poullain de la Barre, the idea that men are superior to women, which was the subject of a tacit consensus at the time, and which he tried to denounce in this book, and which was taken up by Simone de Beauvoir in the middle of the 20th century.
I like this example because it’s quite neutral, it’s not the kind of exaggerated example that you can find for example in the history of science, where much grimmer examples of consensus have occurred in the past. And it’s also amusing to see that nowadays, it’s fashionable to make all kinds of appeals to save the planet. There’s an appeal by a feminist association which believes that saving the planet and acting in favour of sexual equality is the same thing – that’s only a slight exaggeration – it’s interesting to see that these associations base their appeals on a consensus which it seems to me is of the same kind as that described by Poullain de la Barre.
AVR: Quite. In the text the principle argument consists in saying that we often take an appearance of truth for the truth itself. Is that one of your criticisms, Benoît Rittaud, of those you call the carbocentrists – you’ll tell me no doubt what you think they think – whom you contest for the urgent character of their appeal for help and the imminence of climate catastrophe. Is one of the things you criticise them for the fact of taking appearance for scientific reality, is it primarily a scientific argument?
BR: It’s a bit more subtle than that. In this case there’s an alliance between scientists and politicians. And as always in this case this weakens the science, the fundamental principles of science are forgotten, in favour of moralising. These days, if you’re a climate sceptic, you’re immoral, bad. You’re not simply someone who’s mistaken, who needs to explain himself – which is normal in debate – you’re evil. Just a few days ago a book came out published by le Seuil accompanied by an appeal – no doubt Jean Pierre will be talking about it because he signed this appeal – it’s an appeal to stop climate crime, and in which climate sceptics are designated as climate negationists. So we’re no longer in a normal discussion, not even in a confrontation between two opposing camps, because as it happens one of the two camps, the one I call carbocentrists – but there are obviously several different tendencies among them – we’re in a context of criminalisation, with a desire to ban reflection – it’s said nowadays we need to act, the time for reflection is over. When it’s said by politicians – why not? But in the mouths of scientists, intellectuals – people who are in theory more thoughtful, it’s really extremely disturbing.
AVR: Jean Pierre, what is it that you find unacceptable in the position of climate scepticism, and in particular that of Benoît Rittaud here?
JPD: I propose that we don’t talk too much in terms of meta-science, sociology of science etcetera, because there is enough in fifty minutes – there isn’t really time to talk about what is really important, which is to say the epistemology of climate science itself. Because if one starts to talk about meta-science, the murky relations between science and politics, we’ll never get to the end of it and we won’t be able to talk about the important things. One can turn your arguments against you can one not? At the end of your book you say “From a scientific point of view the carbocentrists resemble more and more the walking dead”. I imagine that’s aimed at Jouzel, le Treut etcetera. Not very nice. Ok
BR: It’s an expression
JPD: I propose that we don’t talk about that because the arguments…
AVR: Not talk about what?
JPD: …the epistemology..
AVR: What don”t you want to talk about?
JPD: Oh, oh, the mutual recriminations, the ideology, moralism, etcetera. It’s the same on both sides
BR: The call to stop climate crime came from your side two weeks ago
JPD: Hang on, hang on, hang on. I propose, if you talk about my writing, I propose that you talk about my books
BR: You signed this appeal
JPD: Hang on, hang on, ok. Now..
BR: You signed this appeal
JPD: I agree at least with Benoît Rittaud that the consensus is not in itself a guarantee of truth. Ok, that’s clear. Having said that, you said that most of the time the consensus is suspect
BR: No I didn’t say that
JPD: You said that most of the time
BR: No
JPD: Hang on. If you’ll let me speak
BR: Don’t twist what I said, and I’ll let you speak willingly
AVR: Jean Pierre Dupuy
JPD: Ok, anyway there’s a consensus about – I don’t know – the validity of – a certain validity of – Newton’s theory of universal gravitation, even though we know nowadays that it is false. Ok, which is to say that even the ideas which we hold to be for the most part – not true, but reasonable – in order to conquer – one could recount the history of – I don’t know – the Galilean revolution, the principle of inertia, if you drop a kilo of lead and a kilo of feathers from the top of the Tower of Pisa in a vacuum – there isn’t a vacuum, obviously – they fall at exactly the same speed, that is to say that the force creates, not the movement but the acceleration – for the ideas that we hold today to be basic for rational mechanics to penetrate, there had to be institutions, lobbies, etcetera, etcetera, and we hold them to be true. So, the existence of a consensus is not in itself a sign either of truth or falsity. Good. We agree about that. So, the only thing that counts is the scientific and philosophical quality of the arguments.
AVR: Good. Go ahead, exactly
JPD: So, there’s one thing we agree about, and I propose that we start from this point of agreement. And I say this against the advice of many climato- what do you call them? -centrists..
AVR: carbocentrists
JPD: Yes, carbocentrists – that there’s a huge amount of uncertainty about it. Uncertainty is the key word. Furthermore I wrote a report – two reports even – for the IPCC at the request of Jean Michel Petit about the philosophical nature of uncertainty in climate science. Ok. There’s a huge amount of uncertainty
BR: I don’t agree entirely
JPD: Hang on, hang on..
AVR: Benoît Rittaud, Jean Pierre, present your argument…
JPD: Simply that uncertainty – how can I put it? – you take it for ignorance.
BR: Exactly
JPD: I take it to be indeterminacy. There’s a classic philosophical distinction that one has to bear in mind between epistemic uncertainty and objective uncertainty linked to phenomena. Epistemic uncertainty is “I know or I don’t know”. You ask me “What is the capital of Brazil?” “Rio de Janeiro? Mmm, no. Buenos Aires? No, I don’t know.” When I say that I don’t know, I ‘m saying that I know that I don’t know. But there’s another kind of uncertainty linked to the indeterminacy of phenomena, which is objective, and for which it may well be the case that we don’t know that we don’t know, a bit like the blind spot, if you like, in the centre of the retina, where we can’t see, but we can’t see that we can’t see. Ok. So it’s that kind of uncertainty which interests me. The indeterminacy which occurs in climate science, and it’s that uncertainty which is at the heart of the question of scepticism and truth.
AVR: So…
JPD: I could talk a lot more about it. I hope..
AVR: Yes, quite. Benoît, on this point, is this uncertainty for you, as described by Jean Pierre Dupuy, a reason to doubt the scientific character of the climate catastrophe we’re expecting?
BR: The word “uncertainty” can certainly be used in many different ways. We’re rather in a state of ignorance. We don’t know enough about the climate to be able to claim to predict its future states. We’ve never done it. It’s the first time we’ve said what the climate will be like in 50 or 100 years time – it’s the great difference with the confidence we can have – as you have said before about classical mechanics or quantum mechanics – these are sciences which are well established. We’ve made predictions which have been verified. This is something we’ve never done. One may believe it’s possible. I’m not against trying, but just believing, because it’s science, it’s giant computers, it’s modeling, it’s the consensus, is extremely misleading from an epistemological point of view. It’s a science which is young, which has not yet established itself, which is perfectly normal because the climate system is probably the most complex physical system that we know of. It’s not for nothing that in the sixties Chaos Theory, which we don’t talk much about but which is a real intellectual revolution in mathematics and physics and the natural sciences – Chaos Theory, one of the first articles on the subject was an article by Lorenz where he studied circulation and tried to understand the climate. It’s not for nothing that we talk about the butterfly effect. Everyone knows the butterfly that flaps its wings today in New Zealand and a month later there’s a tsunami or something, because the effects are unpredictable and so – the metaphor of the butterfly effect comes from the meteorological system, the climate, it’s not by chance. It’s really a very complex system. Today we talk about uncertainty if you like. The carbocentrists know well that they can’t reveal too openly their dogma – because it’s become a real dogma – and so they try to show that they are capable of distancing themselves from their work, so they talk about uncertainty. For them, roughly speaking, uncertainty means: “Will the apocalypse take place in 2050 or 2060?” I’m caricaturing a bit but it’s essentially that..
JPD: Yes, it’s a caricature. I’d like to…
BR: I said that I’m presenting a caricature rapidly, but everyone understands what I mean. Roughly speaking they’re saying, the sea will rise two metres, but we don’t know whether it will be in one or two centuries.
AVR: It’s above all the predictability which you…
BR: Are we really in a situation of uncertainty, or are we rather in a situation of ignorance? Have we really got sufficient understanding of the climate system to be able to make predictions? If we compare the predictions made thirty years ago with what’s happening today, they don’t gel. There’s a whole series of things that don’t work. You’ve no doubt heard as I have that the average temperature of the planet has been more or less stable for fifteen or twenty years. Nobody predicted that
JPD: Let me intervene there because it’s becoming a bit too exaggerated
AVR: wait, let him finish
JPD: The problem that I have with climate sceptics is that they’re always bringing up the same arguments. These arguments, you – I mean you the climate sceptics – have been putting forward for twenty years
AVR: So say why you don’t agree with that argument. Go ahead
JPD: Climate sceptics have been repeating it for fifteen, twenty years.
BR: Not for the temperature
JPD: Hang on. Let me..
AVR: Go ahead
JPD: I read your book with interest. I didn’t find anything in your book that I hadn’t already read in the American climate sceptics, which they call over there “Climate Change Deniers” – i.e. climate change negationists
BR: … which you’ve adopted yourself
JPD: Wait, wait. No ad hominem attacks please
BR: You’re attacking when you talk about climate negationists. It’s a serious attack. I’m not sure whether you realise..
JPD: I didn’t say they were negationists, I said “climate change deniers”
BR: Yes you did. You signed the appeal we’re talking about
JPD: Wait please. I want to reply..
AVR: One argument at a time. You were talking about Benoît Rittaud’s book, “The Climate Myth”
JPD: Exactly. So, as I was saying, I didn’t see a single argument which hadn’t already been discussed, and received a response. You have discussed with Jean Jouzel, with Hervé le Treut, etcetera. They have replied to you. You have a very good bibliography in your book. And the unwary reader, with the hundreds of articles, all tending in the same direction, the unwary reader would say; “Ooh la la! It’s an extraordinarily strong movement, climate scepticism!” But the problem is that there are about a hundred thousand articles which take the opposing view, about which you don’t say a word, and which in particular refute everything you say, and in particular the argument that there’s been a pause in the rise in temperature. Ok, there are articles which appeared just last week in Science, Nature, etcetera, which show that this pause is an invention, is an artifact as we say in science, that is to say that it’s linked to the kind of observation that we make, to the type of measurement etcetera etcetera. Ok.
So I want to talk about uncertainty because you say it’s an absolutely crucial point, and you say that it’s ignorance. I made a distinction and I’d like you to take it seriously, the distinction between epistemic uncertainty and objective uncertainty. There’s an example of that which is found in almost all the problems of risk, the environmental problems, and which I had to deal with as part of my job as President of the Ethical Committee of the Authority, the Institute, the Centre for Research on Nuclear Security, the RSN. It’s the existence of events of an extremely low probability of extraordinary magnitude. Ok. In the nuclear case there are two cases, two illustrations of that, the probability of a Chernobyl-type accident, or Fukushima, and the consequences are enormous. The “dual case” as we say in mathematics is the case of a catastrophe, or a – not a catastrophe, of a situation – which seriously affects a very larger number of people, let’s say ten million, but each one of these people infinitely little. In one case it’s infinity, zero times infinity, in the other it’s infinity times zero. So, you have a chapter about Pascal’s wager, and that you conclude in a rather extraordinary manner by saying: “Zero probability a priori that God exists, for example, but the sum wagered is infinitely large and zero multiplied by infinity equals zero.” And you quote Emile Borel, who was a very great expert in probability theory, and a great populariser of mathematics, like yourself, whom I read in the fifties or sixties, but look, Emile Borel was born in 1870-75. Since then, in our thinking about the infinitely small and the infinitely large, we’ve made huge progress. And that’s what I want to talk about.
AVR: What’s the problem with Pascal’s wager?
JPD: We’re talking about philosophy here, really. We’re talking about philosophy. That’s to say, what I want to talk about is something well known in French philosophy, I mean – well known among those who understand philosophy – it’s the Reverend Father Dominic Dubarle in his conceptualisation and formalisation of Hegelian dialectic who used this technique called non-standard arithmetic, which is a way of dealing with the infinitely small and the infinitely large.
AVR: Well known, I’m not sure, so tell us about it.
JPD: I’ll explain. I’ll explain this point which is absolutely essential. And I’d like to discuss this sort of thing!
AVR: Well go on, go on.
JPD: Good. So, in order not to bore the listener, I’ll take an example, which is an example which the American mathematician John Allen Paulos took – it’s an article in the New York Times – during the election campaign between Al Gore and Bush, where it was impossible to come to a decision between them because the number of votes which swung the election was less than the precision of the instruments of measurement which counted the vote. So, he takes the following example. It’s the case of a keeper at the Museum of Natural History of New York, let’s say, who shows the visitors the huge tyrannosaurus which is there in the middle. And he says: ‘This tyrannosaurus is 70,000,006 years old.” Ok, the people hear that and say: “Well, are you sure? 70,000,006 years?” And he replies: “Yes, I’m sure, because when I started work here they told me it was 70 million years old, and that was six years ago.” Ok, that’s amusing, but..
AVR: What’s the conclusion..?
JPD: Hang on.
AVR: Because that’s a while you’ve been talking and one must leave some time for Benoît
JPD: Yes. But I want to conclude my argument
AVR: Exactly. Please do.
JPD: Er, 70,000,006 years. A tyrannosaurus who is 70,000,006 years old, he is seventy million years old. However, the six years in question are important, because if I repeat these six years a million times, I get 70 million plus six million, which makes 76 million, which is significantly different. So you, everything in your reasoning finishes by zero equals zero, as if you counted the six years in question as being zero. Now, philosophers have known this example, known as the Sorites Paradox, or the Paradox of the Heap. Two rocks don’t make a heap. If I add a rock I’ve still got a non-heap. What’s a heap? You can do it with a bald man as well and his hair. What’s a heap? It’s an assembly of rocks. So, you haven’t – you fall there in saying that infinity times zero equals zero into the Sorites Paradox. The consequences of that in the case of Chernobyl are enormous. The official death toll at Chernobyl is 48 deaths, because they don’t count the effect of what we call the feeble dosage which affects each person – there are ten million in the contaminated zone – infinitely little, but there are a lot of people. If you say it’s zero, which is what the Chernobyl Forum did in effect, you get zero, zero
AVR: So it’s the way of calculating that you contest there.
JPD: No.
AVR: Benoît Rittaud? Let him speak
JPD: It’s the philosophy itself of the infinitely small and the infinitely large
BR: Well, obviously I don’t agree with that. I’ll try and explain in a simpler more concise fashion. The chapter you refer to is in answer to the argument that we are not sure – it’s an argument that one hears often when one explains that temperatures are more or less stable, that there a whole lot of things that don’t correspond, in short – people are generally quite receptive to that. But when their backs are to the wall and they try to defend this kind of belief they say: “OK, we’re not sure, but if it’s true, the consequences will be such that we can’t allow ourselves to not act.” And that, I say that..
JPD: That’s not what I said at all
BR: Can I get a word in?
AVR: Let Benoît speak
JPD: I was talking about epistemology and mathematics. I wasn’t talking about catastrophe..
BR: I’m talking about climate. You were talking about tyrannosauruses. Fine, but I’m talking about the climate.
AVR: Benoît, finish what you were saying
BR: So that’s the argument that they make, and what I showed in this chapter of my book is that it’s an argument that goes back to Pascal’s wager, that’s to say, we don’t know if God exists, but if we make a calculation based on probability, it’s in our interest to believe, and Pascal, when he evokes this famous wager, he’s doing so as a mathematician
AVR: …which he is, in fact.
BR: He is, and he’s the main founder of probability theory as well, so it’s not by chance, and it’s interesting to observe that the first application of probability theory to a subject other than games of chance is to theology, which is quite surprising. So Pascal’s wager is: “See, there’s a slight chance, but for an infinitely great gain, it’s in one’s interest to believe.” It’s constructed like that. Pascal’s wager is mistaken. It’s served up in all sorts of circumstances, quite explicitly in the case of the climate, we come back to the wager of Pascal, without realising that the weaknesses of Pascal’s wager are mathematical weaknesses, which he couldn’t know about at the time because the mathematical tools for understanding them emerged only at the beginning of the twentieth century, and they explain that everything depends on the model that he tries to apply to the existence or non-existence of God, like a kind of heads-or-tails, a game of chance, when in fact there are other mathematical models available for understanding this situation, and in these other mathematical models zero times infinity equals zero, and the wager no longer works
JPD: …
BR: Can I finish, can I finish what I was saying?
JPD: Of course, of course
BR: So, there are probabilistic mathematical models under which Pascal’s wager is false. So Pascal’s wager is of no use to us because we can’t know which model is applicable. It doesn’t take us any further, it’s just in order to reply to that particular argument. There’s a very simple argument that was given – not at all mathematical by the way – long before Borel, Lebègue came along at the beginning of the 20th century and the end of the 19th. It was Diderot who said: “Ah, it’s marvellous, Pascal’s wager, but, (he said) an Imam can say just the same thing as Pascal.” Which is to say that with Pascal’s wager you can do absolutely anything you like. You can say: “Yes, why convert to the Christian God (which was Pascal’s aim) rather than to the Moslem God or whatever you like?” You can use the same reasoning. And that’s the problem in the case of the climate, that it’s true that one can say: “We’re not sure, but that could cause a catastrophe,” but you can argue in the other sense: “Yes, but if we act, that also could cause a catastrophe.”
AVR: What actually is your position Benoît Rittaud, what exactly do you not believe, you climate sceptics? Is it the scientific arguments put forward in favour of global warming, is it our responsibility for the warming, is it the political and media use made of ..?
BR: It’s a lot of things together. To be quite clear, I believe the carbocentrists – briefly, those who agree with the IPCC, all those who work for the IPCC – are serious scientists. And it’s what I’ve written, what I believe, and I’ve never..
JPD: You called them the walking dead, the walking dead! What do you expect..?
AVR: …Jean Pierre, otherwise we’ll have to talk about negationism
BR: The walking dead are not the people themselves, it’s the theory.
JPD: Ah! Ah!
BR: Oh yes. You have to read it. Otherwise you twist the words..
AVR: …so that we can get on. So you agree they’re scientists
BR:..real scientists who have made the same mistake as other scientists before them when politics has entered the story, which is that they believed that their specialist knowledge protected them from being exploited. Scientists in general..
AVR: Being exploited in what way?
BR: For political ends. Instrumentalisation. Being used as a political tool. It’s not instrumentalisation in the sense of a conspiracy theory, it’s just the arrival in the political arena of a collective idea, a collective fear, and they’ve been brought in to play a part without really understanding why, without having been prepared. And, as usual – because it’s not really a new phenomenon, there have been other examples in the past, and as usual they’ve been taken for a ride
Voice 3: [my translation of French translation of Al Gore] All the experts agree that it’s we who are responsible for the warming. I’m Al Gore, I’m the ex- future president of the USA. This is Patagonia 75 years ago, and the same glacier today. Kilimanjaro 30 years ago, and last year. In ten years’ time the snows of Kilimanjaro will have disappeared. This is really not a political question, but a moral question. Temperatures are rising everywhere in the world, causing ever more violent storms. The fastest is in the Arctic. If this continues the sea level will rise six metres, and here’s what would happen in Florida, around Shanghai, 40 million inhabitants, the region of Calcutta, 60 million inhabitants, Manhattan, the World Trade Center Memorial would be under water. Think of an exodus of 2000 refugees and imagine if they were 60 million. We have to act together to solve this planetary crisis. It’s our survival which is at stake.

Song: Out where the river broke, the bloodwood and the desert oak, olden wrecks and boiling diesels, steam in forty five degrees. The time has come to say fair’s fair, to pay the rent, to pay our share. The time has come, a fact’s a fact. It belongs to them, let’s give it back. How can we dance when our earth is turning? How do we sleep while our beds are burning?

AVR: Midnight Oil, Our beds are burning, burning, pardon. The first song in 1987 to express awareness of the consequence of the use of [?] and the planet. You’re listening to France Culture… with Jean Pierre Dupuy, author of “For an Enlightened Catastrophism” and “Small Metaphysic of the Tsunami”. Beside him is the mathematician Benoît Rittaud who has published this year “The Exponential Fear”. So, Jean Pierre Dupuy, how do you respond to the statement by Benoît Rittaud that the problem with the carbocentrists, as he calls them, is not so much scientific as with the political and media exploitation, of which we’ve just heard an extract with Al Gore’s celebrated documentary. We can hear clearly the emphatic insistence on a future catastrophism, which has clearly been exploited politically because he was on the campaign trail at the time of this documentary, and does it throw doubt on the validity of the arguments of your position Jean Pierre Dupuy… thinks that there is a real problem with the climate today
JPD: You see, the only really good way to reply to that question would be to do what I’ve been trying to do up to now in this programme, which is to undertake a serious philosophical investigation into the epistemology of the mathematical models of the climate. Ok. But it’s extremely difficult to do in a programme, even an excellent philosophy programme like yours.
AVR: Thank you but please can you reply to the exploitation, the modelisation? your reply…?
JPD: Well, yes, because the only way to justify the work done in climatology is to talk about its models, about its mathematical models, and about the uncertainty which is linked, about .. The thing that’s most extraordinary in Benoît Rittaud’s book is that there isn’t a word, not a single word, about the climate models. There are time series, there are correlations – I know perfectly well that you are a statistician – there’s the saying, no doubt apocryphal, attributed to Einstein, “To a hammer, all problems look like a nail” isn’t it?
BR: That’s not in my book. I don’t know where you got it from, but I didn’t write that. I didn’t quote that
JPD: But anyway, there’s not a single word, not a single word about what a climate model consists of, because it’s a physico-chemical thermodynamic – it’s extremely complex. Anyway, you said so, we agree. But why is it complex? Because there are a load of positive feedbacks, I can give some examples perhaps, a load of negative feedbacks, and the ensemble creates a self-regulating system as my friend, yours also perhaps, Henri Atlan would say, or Francis Coevela [?] – an autonomous system which has its own particular behaviour, that is to say of an endogenic origin, but with, as the climatologists say, two external forcings. One is the cosmic forcing, essentially the variations in the terrestrial orbit around the sun, OK, everything comes from that, I think we can agree, and the other, a much more recent forcing, which is the activity of man. Everything starts… OK. We have to talk about these models. I know that you don’t have much esteem for the models, I’ll read this quote from your book…
BR: Apparently you’ve learned well how to conduct an inquisition. There are the negotiations at Bonn for the climate, to prepare for the COP21. You know there’s an article which proposes the creation of a climate court. You’re well placed because I see that you’re not talking about models and defending your beliefs, but you’re trying carefully to take one sentence that you’ve carefully chosen from my book and trying to tell…
AVR: Talk about the models if you want
JPD: I’m going to read it
BR: Say what you want to say instead of advertising…
JPD: Hold on. “Models are only a rough sketch of the phenomenon – need a model have the greatest difficulty in dealing with the associated theory, or – which is worse – the complete absence of a theory. In the case of climate, we’re in the second situation.”
So, to me, listen, all my scientific and philosophical experience has taught me that there’s no science without mathematical modelling. Imagine Newton’s theory which I mentioned just now, imagine Einstein’s theory or General Relativity without mathematical modelling. The proof is that even the human sciences are fascinated by mathematical modelling, and the only one which has a Nobel Prize, which besides, isn’t a real Nobel Prize, is economics, which shows by the way that the fact of having mathematical models is not a condition – it’s a necessary condition for being a science but it’s not a sufficient condition, that the models can be very bad, you see.
AVR: So for you there’s a model, in order to think about the climate we have to have a model
JPD: But these models exist
AVR: Benoît Rittaud, do you agree
BR: Of course there are models, everyone agrees there are models…
JPD: Let’s talk about these models
AVR: Go ahead
JPD: So, we need to talk about them. Ok, so what causes climate change? Ok, first of all it comes effectively from cosmic causes. Everyone knows that the axis of rotation of the earth in relation to the plane of the ecliptic, that’s to say the plane in which the earth turns around the sun, and – the earth is on a slant if you like, like a top turning, which isn’t always perpendicular to the ground. This angle, we know what it is nowadays, but in fact we’ve only known it recently, even if Rousseau put forward the hypothesis – this angle varies over the centuries and above all the millenia, Ok. Today the earth’s axis of rotation of the earth points in the sky at a star called the Pole Star, which is roughly speaking the star Alpha of the Little Bear constellation. Four or five thousand years ago during the Bronze Age it was a quite different star, which was the star Alpha of the Dragon constellation, and in three thousand years’ time it will be a quite different star. Ok. Rousseau, in his “Discourse on the Origin of Languages” hypothesised that the origin of a civilisation, he thought precisely that it was a sudden catastrophic phenomenon – a “tipping point” as they say in English – which saw the earth’s axis suddenly change direction, which created the seasons, obviously, and the populations gathered in the temperate regions, and that’s how civilisation came about. Now, Rousseau wasn’t entirely wrong, but nowadays we know that this axis of rotation changes all the time, not all the time but over a period of millenia. So that’s the cosmic forcing, you see, which first explains..
AVR: ..the origin of climate change.
JPD: Absolutely. Everything stems from that. So it’s true that..
BR: I don’t know whether..
AVR: You don’t agree..?
JPD: No, but wait, wait.
BR: I don’t understand. You’re talking about the seasons or what?
JPD: The forcing – the best way of refusing to discuss is to say “I don’t understand”
AVR: So tell us…
JPD: The best way, the best way to, the best way to, er, I’ve forgotten my..
AVR: About the model, you were talking about the climate model
JPD: OK, er..
AVR: What is this model? Because obviously you agree with Benoît that there’s a model, so..
JPD: There are lots of them, so..
AVR: So..
JPD: So, the seasons arrive, and that’s the external forcing. Good. But the system as a whole consists of a heap of things, for example, I don’t know, the main greenhouse gas in terms of volume isn’t CO2, it’s water, water vapour
AVR: But I think you agree about that. It’s the nature of the model itself that..
JPD: Let me __Excuse me. So water vapour is a greenhouse gas, and there’s a positive feedback that occurs – it’s just an example to show how complicated it is. The warmer the atmosphere gets, the more water vapour it absorbs. It’s a theorem, or rather it’s a principle of thermodynamics called the Clausius Clapeyron, but never mind. We all know that anyway. So, water vapour is a greenhouse gas. So you have a circular process, a circular causality. The warmer the atmosphere, the more water vapour it absorbs, so the more greenhouse gas it absorbs. And so it increases the greenhouse effect and the temperature. Another positive feedback is the permaprost [sic]
which covers a major part of Siberia, and which, when it melts because of the rise in temperature releases methane – CH4 – which contributes itself, etcetera.
AVR: Jean Pierre, does the presentation of these models allow you to detect the responsibility of man for the warming? Because that’s the decisive point. That the climate changes, everyone agrees
JPD: Ok. You have a multi-causal system of causality which is closed in on itself. Ok right, with an external forcing which is certainly at the origin of everything, which was the cosmic forcing, which I mentioned just now. On that is grafted a forcing which is recent, from about a century ago, let’s say, which is due to the action of man. So you have to understand – that’s where the indeterminacy comes in – you have to understand man’s action as adding the whole endogenic mechanism which produces chaos, oscillations, there we agree – and it’s there that there is a great difficulty, we agree. Er, we have to talk about these models and the indeterminacy. Otherwise we’re just churning out…
AVR: So, do you agree with that?
BR: I’d just say that Jean Pierre has managed to talk – for how long? – without talking about the real model, what a model is. There you have presented the general idea of the IPCC. In fact you’ve spoken about cosmic forcing as the source of the seasons and…
JPD: No, it was an example
BR: Now the seasons are not something recent, known since antiquity. It’s not that, the cosmic forcing. When we talk of cosmic forcing, we’re talking about something quite different, it’s the influence of the sun, the galactic year so it’s something completely different, nothing to do with the seasons. Then, if we’re going to talk about models, since we haven’t – it’s a distinction that you can contest, obviously, a distinction between model and theory. A simple way of putting it is that a theory is something which goes beyond what you can observe directly. Newton’s theory, for example, allows us to predict things, anticipate phenomena, and that provides a conceptual framework that goes beyond the problem that gave birth to it. It’s very rough presentation, of course. While a model has an object which doesn’t change, this object, and one tries to play around with the maths to make sense of it. I realise that it’s very quick because the time is passing. So what’s important to understand in the case of the climate is that there isn’t a theory of climate. We don’t have a global climate theory, to the point that one can ask the question: “Is there such a thing as a global climate?” I want to say something: when we talk about the earth’s temperature, you can attribute a sense to it, but is it really a sense that has a real physical meaning? You can question the method of calculating it – the way you calculate the temperature in a system very non-homogenous like the earth – it’s very cold here, very hot there – according to the way you measure it, you can say it’s warming or it’s cooling, – very interesting questions of mathematics. It really depends on the way you approach the subject.
So we don’t have a theory. On the other hand we have models, that’s to say there are several teams around the world who have made computer models where they try to chop the earth into small bits, each bit is a cell, and then the exchange of heat, exchanges of all kinds, from the air to the ocean are modelled by physical equations, as well as one can, because it’s an extremely complex system. The equations themselves are more or less understood. On the other hand we know very well that we haven’t managed to integrate all the climate variables – there’s a debate to be had about it – and what’s more, the simple fact of running the model means that a small error – it’s the butterfly effect – a small error throws the whole system out. And finally, the model, when you claim that it’s predictive, the least you can do is confront it with observations, and when you compare it with observations you can see that it doesn’t work. The IPCC in 2013 just before the publication of the report had produced a lovely graph which showed the divergence between the models and the observations. This graph was removed. It was in the second…
AVR: It’s the hockey stick.
BR: It’s not the hockey stick, it’s something we haven’t seen, because it hasn’t come out yet. At the last minute it was chopped out
AVR: Ok, but that… right, people make mistakes..
BR: No, the graph showed clearly how the models diverge completely from the observations and it’s something – there are lots of ways of showing it – the predictions of the disappearance of the polar ice by Al Gore quoted just now. The Nobel Peace Prize winner in his speech in 2007 said that the ice at the North Pole, the Arctic ice, will have melted by 2013.
AVR: But it’s one thing to denounce catastrophism, but another to say that no prediction is possible, and that there’s no reason to worry.
BR: One can try and make predictions. That’s science. We need to understand the climate, it’s something useful. We’re very far – the models, there’s a tendency to confuse reality with the future. We make an amalgam between the future and the present:- “Look at the graph”
AVR: That’s part of forecasting
BR: Yes, but one forgets that they are no more than predictions. And we’ve never managed to make predictions of this kind, and they’re predictions using tools which haven’t been tried and tested, and when we look at the observations, that’s to say reality, we don’t see anything very worrying. Obviously there’s something there, the climate is made up of lots of things, there are lots of graphs to look at, to study, and it’s all very well to see if there’s one that goes in one direction or another, but on the whole, there’s not a lot going on.
AVR: So Jean Pierre, do you think the models allow us to predict..?
JPD: No, but, hang on
AVR: .. change of such a magnitude?
JPD: We’re not here to discuss..
AVR: Because in the end that’s the question people are asking
JPD: Remember the words of René Thom: “What counts in science is not to predict but to understand, to explain.” Prediction is something else. Good. So the interesting question is: Do we understand the climate system or not? Ok. I think we understand a very large part, but obviously it’s very complex. I propose that in the few minutes left we talk about epistemology. I thought that was the point of the programme. Benoît Rittaud quoted in passing, though he didn’t dwell on it, Popper and Lakatos. I’m a Lakatian, and I’ll explain what that means. All science is condemned to be wrong. It must be wrong, because if it’s science, says Popper, it’s refutable. The proof that climate science is refutable is that people like Benoît Rittaud are forever refuting it. So it’s refutable. Good. Except that Popper’s refutationism was described by his dissident disciple Lakatos as “naive falsificationism.” It’s the kind of proposition that claims to be scientific: “All swans are white.” I point to one black swan and that’s enough to falsify in the English sense of the word, to refute the original proposition. Lakatos says, but not only Lakatos, there’s the Frenchman Pierre [?] …
AVR: We’ve got one and a half minutes. Finish, Jean Pierre because…
JPD: So…
AVR: The epistemological argument is all very well, but there’s got to be link to the climate, it’s the subject of the programme after all …
JPD: But exactly. Exactly.
AVR: Yes
JPD: Climate science, if it’s a science, it’s false! It’s false! It will be shown to be false, exactly as Newton’s theory is false today because it rests on..
BR: But not at all
JPD: Hang on. Excuse me
BR: But you’re saying what? You refuse Newton’s theory? When you go over a bridge don’t you rely on Newton’s theory? Didn’t you take the Pont d’Alma to get here? Be careful
JPD: … in the sense that Newton’s theory is false in that it…
BR: No, it’s not false, in its domain of validity
JPD: .. in the epistemological sense of the term, in the Popperian sense of the term because it is based on the principle of action at a distance
AVR: There are thirty seconds left Jean Pierre. The climate, with respect to.. come back to the climate, because on the epistemological question we’re a long way away..
JPD: But climate science, which is a science, and therefore potentially false. That’s what you have to understand. Ok, It will be refuted..
BR: So there you agree with Benoît Rittaud in that case
JPD: No because he, like all the climate sceptics, allow me, you’ll allow me to say that you’ve lost the battle of public opinion because.. which doesn’t show that you’re wrong..
BR: It’s you who’ve…
JPD: You’ve lost the battle of opinion. You have the Pope, the Governor of California, Obama, the President of the French Republic…
BR: If you ask me..
JPD: In the public, you’ve lost, that doesn’t mean you’re wrong..
BR: There was a survey carried out by the UN which asked in the whole world in 1xx countries to rank in order the main problems that showed very well…
JPD: I thought this programme would be an opportunity to talk about things which are really serious, by which I mean..
AVR: We gave you the chance for fifty minutes. It’s not easy…
JPD: I know, I know…
AVR: Thank you for having taken part, Jean Pierre Dupuy and Benoît Rittaud