Scepticism is often discussed in connection with climate change, although the concept is often abused. I therefore thought it might be interesting to go back and see what the epitome of 20th Century sceptics, Bertrand Russell, had to say on the subject. This is extracted from the Introduction to his ‘Sceptical Essays’ (1928):
I wish to propose for the reader’s favorable consideration a doctrine which may, I fear, appear wildly paradoxical and subversive. The doctrine is this: that it is undesirable to believe a proposition when there is no ground whatever for supposing it true.
First of all, I wish to guard myself against being thought to take up an extreme position. … [Pyrrho] maintained that we never know enough to be sure that one course of action is wiser than another. In his youth, … he saw his teacher with his head stuck in a ditch, unable to get out. After contemplating him for some time, he walked on, maintaining that there was no sufficient ground for thinking that he would do any good by pulling the old man out. … Now I do not advocate such heroic scepticism as that. I am prepared to admit the ordinary beliefs of common sense, in practice if not in theory. I am prepared to admit any well-established result of science, not as certainly true, but as sufficiently probable to afford a basis for rational action.
There are matters about which those who have investigated them are agreed. There are other matters about which experts are not agreed. Even when experts all agree, they may well be mistaken. …. Nevertheless, the opinion of experts, when it is unanimous, must be accepted by non-experts as more likely to be right than the opposite opinion. The scepticism that I advocate amounts only to this: (1) that when the experts are agreed, the opposite opinion cannot be held to be certain; (2) that when they are not agreed, no opinion can be regarded as certain by a non-expert; and (3) that when they all hold that no sufficient grounds for a positive opinion exist, the ordinary man would do well to suspend his judgment.
So does this provide any clarity? Russell clearly doesn’t support an extreme where everything must be continually doubted and nothing can ever be known. As he later suggests, that kind of position would make it philosophically troubling to ever get out of bed in the morning. This extreme attitude does however rear up in climate discussions where an interesting debate on the impacts of human-related increases of greenhouse gases on, say, the atmospheric circulation, often becomes bogged down in how do we know that GHGs are increasing at all, whether they are affected by human activity, and how it’s all down to the sun anyway. Since all of these things have been discussed ad nauseum here, here and elsewhere, that kind of ‘scepticism’ (more accurately described as contrarianism, or ‘la-la-la-I-can’t-hear-you’-ism) serves only to waste time. Since working scientists are all busy people, this is usually why we tend to cease communication with such contrarians very quickly.
If we relax the above-mentioned constraint requiring ‘all experts’ to agree (something never achieved in practice) to ‘the overwhelming majority of experts’, we can substitute in the IPCC for ‘experts’ in the quote. It’s important to note that Russell does not claim that if all experts are agreed, then one must agree with them, but solely that being certain of the opposite opinion in such circumstances is not wise. It is implied by his opening statement then that having ‘all experts’ agree something is reasonable grounds for supposing something to be true. Similarly, if the IPCC concludes that something is highly uncertain (such as the magnitude of changes in aerosol indirect effects), then there are no good grounds for assuming otherwise.
Can someone be productively sceptical? Of course. Firstly, one needs to be aware that scepticism about whether a particular point has been made convincingly is not the same as assuming that the converse must therefore true. Sometimes scientists just don’t use the best arguments they could (particularly if they are a little out of their field of expertise) and these points can, and should, be challenged. One example would be the use of an incorrect ‘correlation implies causation’ argument. For instance, the strong correlation of CO2 and temperature in the Antarctic ice core records does not in and of itself imply that CO2 has a radiative impact on climate. However, additional analyses that look at the factors controlling temperature during the ice ages give strong grounds for believing that CO2 does play an important role. Therefore while the use of the correlation argument alone is wrong, the converse of the conclusion is not necessarily true.
Secondly, it helps to have done the homework. It is highly unlikely (though not impossible) that the sceptical point in question has not already been raised in the literature and at meetings. If a particular point has been argued to death previously and people have moved on (either because it was resolved, moot or simply from boredom), there is little point bringing it up again unless there is something new to talk about. Obviously, a good summary of how the point was dealt with can be educational though. Arguments about whether the current CO2 rise is caused by human activity fall clearly into this category.
Thirdly, scepticism has to be applied uniformly. Absolute credence in one obscure publication while distrusting mountains of ‘mainstream’ papers is a sure sign of cherry picking data to support an agenda, not clear-thinking scepticism. Not all papers get the peer review they deserve (or require) and the literature has many examples of dubious logic and unsupported interpretation. Sometimes this becomes very clear (for instance, the Soon and Baliunas saga at Climate Research), and sometimes it goes uncommented upon. But what about Galileo? Wasn’t he an obscure scientist persecuted by an entrenched mainstream? Yes, but Galileo is celebrated today because he was correct, not because he was persecuted. If an idea is right, it will be supported by additional evidence and will lead to successful predictions – at which point it will likely be accepted. The ‘Galileo’ defence (and its corollary the ‘establishment conspiracy’) are usually a sign that the additional evidence and the successful predictions are lacking.
Finally, it should be understood that constructive scepticism is a mainstay of the scientific method. The goal of science is to come closer to a comprehensive picture of how the real world works, with scepticism essential to toughening up scientific ideas, though alone, it is insufficient to move understanding forward. It isn’t essential that every true sceptic have an alternative theory ready to go, but they should bear in mind that our picture of how the world works, though incomplete, rests on many different foundations. If it sometimes seems that the scientific consensus is resistant to new ideas, it is because that consensus has already been tested in many ways and yet still stands.
Much of what passes for ‘debate’ on climate change in the popular media, is often framed as the ‘scientific consensus’ vs. the ‘sceptics’. A close examination of these arguments (for instance, as outlined in a recent Wall Street Journal editorial) doesn’t reveal much that could be described as true scepticism since they often use the fallacious reasoning that we discuss above. However, since scepticism has a (justifiably) long and noble tradition in science, the framing device is quite powerful (despite the lack of connection with any actual scepticism). As with the intelligent design controversy, agenda-driven opposition has often managed to cloak its contrarianism with the mantle of scepticism. So, while many contrarians pay lip service to the legacy of Russell (or even Pyrrho), forgive me if I remain a little sceptical…