It is troubling that the proper methods of scientific argument are not being brought to bear on the issue of global warming. This issue is meant to be based on good science practice, scientific evidence and the evaluation of that evidence. Briefly to run over the background science, the presence of carbon dioxide in the atmosphere creates a greenhouse effect which contributes to keeping the atmosphere warm. This is accepted by all scientists. The global warming scenario then arises because we have injected a good deal of carbon dioxide into the atmosphere through our activities - such as burning coal. This extra carbon dioxide may cause the atmosphere to warm to unnaturally high temperatures with potentially devastating consequences. Scientists have spent many years trying to discover if this scenario is correct. Environmentalists say yes, skeptics say no. Among the scientists, the great major say yes but a small and vociferous minority are crying no! What are we to make of this?
The way scientists work is as follows. We scientists, and I am one of them, have some hypothesis, some idea which we want to test. We make observations and do experiments, often backed up by calculations. What we look for is some test that can in principle prove that we are wrong; that is, we look for tests that could in principle show that our hypothesis is incorrect. It is essential that such tests exist. If you can come up with no test which you can perform which may in principle show that your idea is wrong, scientists will rightly turn their backs on you. This may at first seem a bit odd, but it is the way we work. What you do is to show that neither you nor anyone else else can show that you are wrong; ergo, you are probably right! Remember that an observation that fits with your hypothesis is not in itself proof that your hypothesis is correct, since who is to say that some other hypothesis might not even fit the observations just as well?
Let's give an example where two competitive ideas came into collision. A classic case of this is the Copernican system vs the age-old Ptolemaic system of the sun and planets. The Copernican system with the Sun at the center was not accepted on both scientific as well as religious grounds at the time when it was promulgated, because the Ptolemaic system worked just as well - in fact better in some ways. There was no clear way to prove either system wrong, at the time.
Another and recent example is the ozone depletion problem of the 1980s and 1990s. The hypothesis is (was) that the release into the atmosphere of the chemicals used in bridges, and for hairspray and so on, could cause ozone to be depleted in the upper atmosphere. The test to show that this could be wrong is as follows. If we observe the ozone concentration in the upper atmosphere over a period of time and find that it is not reduced, then this falsifies the hypothesis that human actions are causing ozone depletion - since there is nothing to explain. Note that the opposite observation of finding depletion of ozone does not prove that human actions are causing ozone depletion. Something is doing it, but not unnecessarily human action.
A positive observation of depletion therefore leaves the question open of whether depletion is natural or due to human activity. All we can do for certain is to falsify the hypothesis that human activity is causing ozone depletion. What actually happened with ozone was the discovery of a massive ozone hole over the Antarctic, representing a dramatic depletion of ozone. Coupled with sound observational evidence of all sorts, for which a Noble Prize was given, this ozone hole lead to swift and decent international action in the form of the Montreal Protocol. Thus while we can initially only falsify a hypothesis, the great weight of evidence can be extremely convincing of the truth of a hypothesis. The risk that we were the cause of the ozone hole was very great indeed.
The same scientific method is not being applied in the case of the global warming debate. Indeed this method can not, in my opinion, be applied. However, the dispute is presented as essentially a scientific interview, with the many political and economic ramifications which follow put forward as resting upon the results of an objective scientific debate. I would contend that it is not an objective scientific debate, simply because the rules of science are not being followed. I suggest instead that it is a debate about perceived risk. What is the risk of the climate skeptics being wrong? What is the risk of the environmentalists (if I may call them that) being wrong? Rather than go on in this dry manner, I should like to present the reasons for my view by recasting a fictional conversation between two physicists, Horace and Twinkle.
Before we start, I would like to remind you that there are two types of climate skeptics: the absolute skeptics who deny that there is any global warming at all and the relative climate skeptics who agree that there is evidence for global warming but that it is not caused by our introduction of additional carbon dioxide into the atmosphere, that is, it is not our fault. Rather, the observed warmth is just some part of a natural warming cycle. Horace below lies somewhere in between, mostly relative but with a touch of the absolute.
Enter Horace and Twinkle; they sit down together with their coffee in the cafeteria on the seventh floor of a famous Physics Department, which will remain unnamed. The cafeteria overlooks the harbor and you can see way over to the hills on a clear day like the present one. But it's not the view that interests them. It's an old theme which they focus on. Horace is a climate skeptical. Twinkle, his friend, believes that humans cause global warming and that 'something must be done about it'.
'So the Copenhagen Climate Meeting has started,' Twinkle remarks, to get the ball rolling.
'Yeah,' Horace replies. 'Let's see if some decent arguments come up this time instead of just the repetition of the catechism of the faithful environmentalists!'
'Now, now,' mutters Twinkle, sipping his coffee.
'Well, you know what I mean,' says Horace. 'You can see what those e-mails from the University of East Anglia are saying. It's a bit of a put-up job. '
'I have not read them. I suppose I should, 'replies Twinkle. 'But it's the normal story. The skeptics say the e-mails change everything and the main-line people say they change nothing. You heard the Saudi representative at the Copenhagen Meeting. Talk about self-interest. '
'Yes, but he may be right! The climate has been changing over time, fluctuating a lot. How can we possibly know that it's due to human activity? '
'Look, we do know something. First of all the people people tell us that the temperature is rising so very fast that it's got to be unnatural. And all the models show that if you put more CO2 in the atmosphere, this will cause the temperature to rise. We have put more CO2 in the atmosphere. The temperature is rising. It speaks for itself! '
'Yes, you're right in principle. I accept that, more or less. I am not so sure about the temperature rise. But that's not the point. '
'What's the point, then?' Twinkle objects in as Horace pauses for a swig of coffee.
Horace holds up his hand.
'You know as well as I do that the models are .....' he starts.
'May I join you?' Socrates, the new professor from Greece, puts his tray down on the table beside them.
'Yes, yes, of course,' says Twinkle. 'We were just talking about the climate meeting in Copenhagen.'
'Yeah, I was just saying that these climate models are really poor,' starts Horace again. Socrates nods and Horace continues. 'The biosphere is not coupled in and the worst part is, from a physics point of view, the treatment of clouds is just completely unrealistic. We simply can not predict the amount of temperature rise associated with adding a certain amount of CO2 to the atmosphere. '
'The models are really so bad?' Socrates requests.
'Clouds are the key,' says Horace.
'So you would not trust any of the predictions of the models?' requests Socrates.
'Except the general result that putting CO2 into the atmosphere causes warming - Horace agreements with that,' puts in Twinkle.
'Yes, but how much warming?' says Horace. 'I do not trust the numbers that people come out with. There could be quite insignificant effects. Perhaps it is not important what humans have done. Maybe natural changes are much more important. The models can not prove anything! '
'Oh! God! ' says Twinkle. It is not clear whether this is an expression of general dismay or particular dismay with his friend and colleague Horace. The three sit silently for a few moments, drinking their coffee. The silence is broken by Socrates.
'Could I ask you something, Horace?'
'If I were to ask you, what single piece of evidence would make you change your mind and say that you were wrong'
'You mean observational evidence?'
'If you like,' replies Socrates.
'Well,' says Horace. And then there is a silence as he mulls the question over. 'That's an interesting question.'
'He'd like to see a ten degree rise in temperature and then he would know that he's wrong,' puts in Twinkle mischievously.
'I did not say that!' says Horace, grinning at his friend.
'Well, we're waiting. What would convince you that you are wrong? ' requests Twinkle.
'Maybe I may ask you the same question, Twinkle?' says Socrates. 'What would convince you that the skeptics were right all the time?'
'A drop of ten degrees in temperature!' says Horace laughing.
There is silence again. But this time it is a different sort of silence. Horace and Twinkle are thinking.
'Well obviously,' says Twinkle after some time, 'if we went on at the present rate of putting CO2 in the atmosphere, and the temperature did not rise, well then ..... say in the next fifty years .. .. '
'What about you, Horace?' requests Socrates as Twinkle dwindles to a halt.
'I'm not sure that there is one thing that would prove to me that humans are causing significant global warming,' replies Horace. 'Perhaps a set of factors,' he adds.
Horace and Twinkle look at each other and frown. They both know perfectly well that a theory is not a theory without it is in principle disprovable by some experiment or observation - or at least by a decent 'thought experiment'. Socrates crystallizes their unease.
'I wonder if one could say, then, that global warming is not so much a theory as a feeling?' and he gives a little embarrassed laughter.
'Well, there are things that might prove it, one way or the other. My point is that it's far from proven, 'says Horace.
'Yeah. But we were asked what would disprove our view! ' retinks Twinkle. 'And what's more, any experiments which you're contemplating are not experiences which we are willing to risk doing, are they? Like doing nothing and waiting fifty years! That's the problem! '
Horace pulls a wry face but does not actively disagree.
'Could it not then be put down to a question of perceived risk?' requests Socrates. He pauses a moment. 'Since global warming looks undisprovable,' he adds.
'You mean, what's the bigger risk? - that I'm right and he's wrong, and vice versa? ' requests Twinkle
'Hey, wait a moment, I ....' says Horace, seeing a problem looming.
'Well, you have to admit since none of us has an acceptable proof, or rather disproof, then it does come down to risk, does not it?' interrupts Twinkle.
'You mean that there's worse consequences if the skeptics are wrong?' requests Socrates, turning to Twinkle.
'I should say so,' says Twinkle, 'would not you?'
'Look, this is daft.' Horace sounds a bit riled. 'On this basis, anyone could predict the end of the world, and because we can not disprove it, we have to act, turn the place upside down. That's not science, it's anarchy! '
'Yes, that's a good philosophical point,' says Twinkle. 'I'm absolutely with you that if I come with a crazy theory, it's up to me to try and prove it, not for you to disprove it. But there's two points here. First, we agree that global warming can not be proved or explained in a way that would satisfy us. Second, it's not a crazy theory .... not really a theory at all, after what Socrates has asked us. But it has a sound qualitative basis, though not quantitative, I agree. I think Socrates has asked the right question. What observation would convince you that you are wrong? I do not have an answer. You do not either. So it's risk that we're talking about, not decent rigorous science. The risk of you being wrong is worse, Horace, than the risk of my being wrong. '
Horace grunts but holds his peace.
What's the conclusion? I suspect that the great majority of people would follow Twinkle. The adverse effects of the environmentalists being wrong are fundamental of course, since we would be using so many resources, human and natural, in a very inefficient manner by combating a non-persistent problem. Perhaps the rate of growth of the world economy would be slower than it would otherwise be. However if Horace is wrong, and we do nothing or very little on his advice, no amount of bank survival packages, announcements by the Chairman of the Federal Reserve or wisdom from whatever source, will save us from a range of opponents, the least of which may be a great calamity. Most people, and almost all nations at the Copenhagen meeting, advocate the 'principle of precaution'. They fall on the side of Twinkle. Precautionary measures must be taken.
The piece above provides a rather different way of looking at the global warming debate. It is somewhat liberating because, in the way that the debate is generally presented, it is quite impossible for non-experts to understand what the scientists are arguing about, even when the arguments are between the environmentalists alone. One says that the sea level will rise by 3 feet, the other say 6 feet! How are you to know who is correct? You can not make up your mind on the impact of global warming by listening to climatologists disagreeing about which is the better general circulation model of the atmosphere of the Earth! My view set out above is that the global warming debate is not founded on science because the proper application of standard scientific argument is lacking. Therefore the non-scientist is free to make his or her own choice on the basis of how they see the risk, without feeling that their lack of expertise disqualifies them from holding an opinion.