AUSTRALIA is faced, over the next generation at least and almost certainly much longer, with two environmental problems of great significance. They are, first, how to manage water and, second, how to find acceptable alternatives to oil-based energy. Global warming is not one of those two issues, at least for me, and I see it as a distraction.
I am going against conventional wisdom in doing so. But Western societies have the standard of living, the longevity and the creativity we have because we have learned that conventional wisdom has no absolute status and that progress often comes when it is successfully challenged.
If you listen hard to the global warming debate you will hear people at every level tell us that they don't want to hear any more talk, they want action. I feel that the actions I have seen proposed, such as carbon caps and carbon trading, are likely to be unnecessary, expensive and futile unless there is much stronger evidence that we are facing a global environmental crisis, whether or not we have brought it about ourselves.
The story about anthropogenic global warming (AGW) doesn't seem to stack up as the best science, despite the supposed consensus about it among "thousands of scientists".
Indeed, the insistent use of the word consensus should cause those who are knowledgeable about research to raise their eyebrows, because research and science aren't about consensus, they are about testing theories against data.
In any case, there exists vigorous debate throughout the climate change domain. For example, there is disagreement about whether 2007 was a notably warm year (it had a hot start but a downward cool trend). And all that is simply about measurement. In climate science I see no consensus, only a pretence at a contrived one.
Despite all the hype and the models and the catastrophic predictions, it seems to me that we human beings barely understand climate. It is too vast a domain. Though satellites have given us a sense of the movement of weather systems across the planet, portrayed every night on television, we still know little about the oceans, one of the crucial elements in climate processes, not much more about the atmosphere, another such element, a little about solar energy and the effect of the sun's magnetic field on Earth, and only a little about the land. The Earth is a big place.
One of the yardsticks of the debate is average global temperature. We can all imagine what it might mean: an average of the temperatures taken in a multitude of carefully plotted points across the globe, measured the same way, providing a single figure that could be measured over time to show trends. The actuality is much less. NASA's Goddard Institute for Space Science, the National Climate Data Centre and the Hadley Climate Research Centre in Britain produce the data. All use temperature data recorded 1.3m to 2m above Earth's surface and obtain an arithmetic average of the maximum and minimum temperatures over 24 hours.
None covers the entire planet, and the southern hemisphere is not as well measured as the northern.
A recent study of one-third of the sites in what is arguably the best temperature measuring system, that of the US, showed that in a majority of the sites surveyed the instruments were inappropriately located: close to buildings, on asphalt or concrete, next to parking areas, on top of roofs, and so on. Common sense tells us that if our knowledge of climate and weather cannot provide forecasts with much accuracy past 24 hours, we don't know enough about the inter-relationships inside the model, no matter how much data we have, even supposing it to be perfect data. Models are models: they are highly simplified versions of reality and cannot provide evidence of anything.
What I see, rather, is something that political theorist Paul Feyerabend wrote about a long time ago in Against Method (1975): the tendency of scholars to protect their theories by building defences around them, rather than being the first to try to demolish their own proposition.
We seem to be caught up in what a pair of social scientists has called an "availability cascade": we judge whether or not something is true by how many examples of it we see reported. Fires, storms, apparently trapped polar bears, floods, cold, undue heat: if these are authoritatively linked to a single attributed cause, then almost anything in that domain will seem to be an example of the cause, and we become worried.
I should say at once that climate change has become the offered cause of so many diverse incidents that, for me at any rate, it ceases to be a likely cause of any.
Greens and environmentalists generally welcome the AGW proposition because it fits in with their own world-view, and they have helped to popularise it. Governments that depend on green support have found themselves, however willingly or unwillingly, trapped in AGW policies, as is plainly the case with the Rudd Government. The hardheads may not buy the story, but they do want to be elected or re-elected.
In short, AGW is now orthodoxy, and orthodoxy always has strong latent support. Because AGW is supposedly science, even well-educated people think it will be too hard for them.
David Henderson, a respected British economist and former Treasury official, has called the orthodoxy in climate change a case of "heightened milieu consensus", in which prime ministers and other leaders tell us that nothing could be more serious than this issue. These are not statements of fact; they are no more than conjecture. But they have become, in his phrase, "widely accepted presuppositions of policy". Intellectually, AGW is what is known in politics as a done deal. But on the evidence that is available, I think it has to be said that the assertion that the increase in carbon dioxide has caused the temperature to rise is no more than an assertion, however attractive or worrying the association may be. There is simply no evidence that this causal relationship exists.
Earth's atmosphere may be warming but, if so, not by much and not in an alarming or unprecedented way. It is possible that the warming has a "significant human influence", to use the term of the Intergovernmental Panel on Climate Change, and I do not dismiss the possibility. But there are other powerful possible causes that have nothing to do with us. If this were simply an example of scientists arguing among themselves, we might recognise that this is how science proceeds and move on.
But if there is no true causal link between CO2 and rising temperatures, then all the talk about carbon caps and carbon trading is simply futile.
But it is worse than futile, because one consequence of developing policies in this area will be to reduce not only our own standard of living, but the standard of living of the world's poorest countries.
As someone who has worked closely with ministers in the past, I cannot imagine that I could have advised a minister to go down the AGW path on the evidence available, given the expense involved, the burden on everyone and the possible futility of the outcome.
Some readers of drafts of this paper have raised the precautionary principle as an indication that we should, even in the face of the uncertainty about the science, take AGW seriously. Unfortunately, as I see it, the precautionary principle here is very similar to Pascal's wager.
Pascal argued that it made good sense to believe in God: if God existed you could gain an eternity of bliss, and if he didn't exist you were no worse off. Alas, Pascal didn't allow for the possibility that God was in fact Allah, and you had opted for belief in the wrong religion.
The IPCC's account of things seems to me only one possibility, and the evidence for it is not very strong.
For that reason, I would counsel that we accept that climate changes, and learn, as indeed human beings have learned for thousands of years, to adapt to that change as rationally and sensibly as we can.
This is an edited extract from a paper presented to the Planning Institute of Australia. Professor Don Aitkin, historian and political scientist, is a fellow of three learned societies.