(AKA The Rumsfeld Conundrum)
Following on from a discussion amongst a number of internet friends at Planet 3.0, The Usefulness of Knowing what we don't know , it occurs that, since I was educated in Philosophy (specifically Epistemology) by some of the players mentioned in the literature, and on the basis that some of their cleverness might actually have been absorbed, I might have something useful to say on the matter.
It's important not just as an intellectual exercise (of the type that causes non-philosophers to tear their hair out and kick things) but also because even a cursory exploration of some of the more modern ideas of knowledge, belief and justification can lead us down some revealing paths when we look at the expert/public interface in science and the media.
It's also revealing of something else - the motivations for 'skepticism' and the reasons why some people (without trying to judge them) are still not convinced by some arguments and conclusions arising from climate science and the policy implications of AGW.
In general, Epistemology is the Theory of Knowledge ; in other words, attempts to address or answer questions such as 'What do we mean when we make a claim to know something?' Immediately it is clear that this is relevant to climate science discourse, since many of the things which are traditionally associated with a 'common sense' understanding of what constitutes 'knowing' are challenged by 'skeptics'; from what fundamental 'facts' are to be accepted, to what counts as evidence in support of AGW, through to more sophisticated problems such as whether there is justification for certain policy decisions (such as the immediate mitigation of AGW via CO2 emissions management).
The first thing to observe is that much (most?) of the public discourse, though it sometimes appears to be about what is 'known', actually revolves around what different people believe, and the reasons why they believe these things (in epistemological terms, justification). One of the reasons for this is that Climate Science is not an easy thing to do or test, and most of the public discourse is amongst people with varying degrees of ignorance (with some notable exceptions, such as RealClimate). We frequently hear scientists voicing concern over the public interface and the difficulty of communicating effectively, but the problem won't go away easily, because a lot of the work done by 'skeptical' communicators is aimed (directly or indirectly) at reducing the epistemological status of the science, the scientists, and the milieu in which the science is undertaken. By this I mean that the justifiability of a certain scientific proposition is undermined, creating doubt amongst some of us who don't, or can't do the actual science, or even fully understand the methods.
We often find it hard to see another person's point of view if we disagree about the 'facts' or the 'conclusions' of a position, regardless of the reasoning either has undertaken to reach the conclusion. In other words, we start with a problem of Belief. There are many ways to reach a condition of believing in the truth of a proposition, some logical, some rational, some intuitive, some pre-conditioned. It can be revealing to ask a person who you disagree with, why they hold that particular belief. In the case of we ignorant masses (the 'non-climate-science community'), investigation leads down any number of paths, but often reduces down to a relatively small number of core, or foundational assumptions about ourselves, the world and how we interact with it. Sometimes, these fundamentals are derived from religious or spiritual beliefs, which hold a privileged status in our personal epistemological landscape, and are therefore highly resistant to challenges, not least because they are often self-consciously 'irrational' as well as being deeply embedded in our psyches.
So, how can we make progress, about what we can claim to 'know' about climate science, or about why emissions controls (regulation, taxation, limitation of freedom, of trade, of wealth) matter now?
One way is to shift the epistemological landscape to newer ground, from the 'traditional' or 'common-sense' notions of truth, knowledge, belief and justification, to more modern, 'hard' notions of knowledge and belief, such as Bayesian Confirmation Theory, or Bayesian Social Epistemology. Without going into the details here, since they are well expressed elsewhere, for example here), this can lead down tracks such as betting on climate change, a popular and readily understood activity which has the power of publicly testing both the credibility of a person's stated belief (how much they really believe it being measured by how much they are willing to bet on it), as well as the actual grounds on which two differing views are justified, in relatively simple and measurable terms.
For scientists, there is appeal in the betting meme, since it relates to some very interesting ideas about probability and statistics, exemplified by what are known as Dutch Book Arguments. This type of discourse - the climate bet - (see here, for example), is accessible and its results understandable, with the added piquancy that someone is going to get 'smacked down' by the result. For the public, it can work as an immediate measure of the sincerity of the exponent of a given belief, which in turn has an effect on the justification for believing in that person's stated belief (both in common-sense, and Bayesian terms).
Yes, it is essential to have a sense of 'what we don't know'. In climate science discourse, most of us are obliged to confess that our personal beliefs do not depend on first-hand science; we must depend on others to provide the evidence, so our beliefs are more or less justified by the weight, credibility and logic of others. But we also can have a sense of what we should be able to claim to know, without too much controversy, and it is important for the discourse that climate scientists understand that communicating this is still very important. But enough for now, so later I will look at trying to find the grounds (fundamental principles) for a claim to know that policy action is no longer avoidable.