The BBC reports that "Gordon Brown is "unequivocal" about the scientific case for action against climate change, No 10 has said, ahead of the forthcoming Copenhagen summit." But there isn't a scientific case for policy action against climate change. There is never a scientific case for policy action against anything.
There can be scientific cases against action. For example, if scientific research suggests (as it does) that there is no basis whatever for health concerns regarding mobile 'phone booster stations, that's a pretty good reason not to enact policy action restricting the placement of such booster stations on health grounds. (It may not be a decisive reason, of course, and there may be other reasons that health grounds for enacting such restrictions, but it is a case.) Scientific research or theory might also tell us that an intervention wouldn't work. For example, if we tried to stop swine 'flu from spreading by slaughtering all the pigs in the country but scientific research suggested that this would have no impact on the spread of swine 'flu, that would be a good reason not to enact the policy.
But science can't tell us that we should act. Because acting always involves costs and opportunity costs. And it is not a matter for science whether it is worth bearing those costs; neither is it a matter for science how we evaluate whatever benefits of action science might suggest there are.
Thus, some scientists believe that there should be no manned exploration of space, but instead all funds available for space research should be spent on unmanned probes. But it should be fairly obvious that this is not a scientific question - it is a policy matter whether we would prefer to spend our taxpayer funds on manned or unmanned exploration. It is not up to scientists, alone, to tell us that we should not send people into space.
Some scientists believe that children are better raised without being smacked, and that smacking should be banned. But banning smacking involves a significant infringement upon the liberties of parents, as well as costs of enforcement. The science alone can offer no comment on these.
Some scientists believe that alcohol and tobacco should be banned, as addictive and destructive substances. Do we believe that what ought to happen, in practice, should depend on a scientific debate? That such a ban can only be avoided insofar as we can cast doubt on the scientific validity of the arguments concerning the addictive properties of the substances involved or the harm they cause?
I put it to you that almost no-one would imagine that any of these cases are determined by the science alone - that there is a "scientific case for action" over any of these matters. So why do people imagine that there is a "scientific case for action against climate change"? Why do they not suppose that this is a policy matter, in which we need to take account of the costs of forbidding things or spending resources on our favoured technologies, research, and enforcement? In which we need to ponder how we assess the benefits of action (How much is it really worth to us for people in Britain in a hundred years time to be 2.9 times as rich as we are as opposed to only 2.7 times - even if that were true?)? In which we need to question whether the proposed routes forward are the best ones? In which we do not need to worry about whether some better way forward may present itself in 20 years time?
I suspect the reason is this: people have been conned into believing that standard theories about climate change suggest there is a significant risk of the world ending unless we act now. Of course, even if the world really were going to end in 100 years time, it's not completely obvious that I would want to do anything about it - I might well be dead by then, and just not care. But let's suppose, for the sake of argument, that if the world really were going to end, then we ought to do something to prevent it if we could. And let's suppose, also, that we could actually do something (which isn't obvious at all). Fine. So, if climate change models made robust predictions that the world were going to end some time soon unless we act now, one could (sort of) say that there was a "scientific case for action against climate change".
Except that they don't. Not even close. Standard climate change models simply do not suggest that the world is going to come to an end if we do not act now. Quite apart from not suggesting that this is what to expect, they don't suggest that there is a significant risk of this. They don't even suggest that there is a small risk of this. Films like "The Day After Tomorrow" are no more scientific than "2012" or (for that matter) "The Wind in the Willows".
But climate scientists (at least, the considerable majority of them) seem to believe that we should act to prevent the significant warming that they predict (on the basis of models that embed assumptions about the growth of economies and the development of technology that are definitely not scientific, belonging to other disciplines such as economics). They don't go around emphasizing that they don't believe that this would be the end of the world. They don't go around telling us that they think that even despite this warming people across the world would be vastly wealthier than today, and hence equipped with far greater resources than we are to tackle the challenges involved.
Why not? I think it's because they think something should be done about it, and they would prefer the decision to be up to them. They see themselves as benign guardians of us, the ignorant masses, and they fear that if we really understood what was the nature of the tradeoffs and uncertainties involved, then we wouldn't do anything to try to prevent global warming.
Don't let them get away with this. We are talking about decisions involving huge percentages of world GDP and enormous impacts on the growth rate of economies over decades. Climate scientists are not remotely qualified to comment upon the consequences of their preferred forms of state intervention upon economic development, the lot of the poor, the progress of human endeavour and enterprise, human freedom, political systems, relative military power, or almost any of the topics that ought to be central to decisions on this scale.
There is not a scientific case for action against climate change. There is a scientific case that the earth is warming, that it will continue to warm, and that human action has something to do (and will, unless action is taken, continue to have something to do) with that warming. The science is one input into the policy decision as to whether action should be taken against climate change (and, if so, what action). But it is only one input. It is long past time the main debate moved onto the other matters that should enter into the decision.
