Excerpt from the ABC's Editorial Policy 7.4.1: where topical and factual content deals with a matter of contention or public debate, a diversity of principal relevant perspectives should be demonstrated across a network or platform in an appropriate timeframe.

When Mark Scott writes about whether the ABC should be sold off, a startling number of the posts that follow are about the ABC's alleged political bias. 'Bias', too much of it, and 'balance', the lack of it, are by far the major pre-occupations of those who complain to, or criticise, the ABC.

'Bias' is notoriously difficult to pin down. After all, where one listener hears 'right-wing bias', another will hear a 'rare exhibition of balance'. And vice-versa. The ABC's traditional defence is to quote the regular polls it commissions. Last year, 88 per cent of the sample thought the ABC 'does a good job of being balanced and even-handed'.

But the ABC's program makers are constantly engaged in abstruse debate, between themselves and with their public, about what balance is required, and when, and how.

A dispute is raging right now about The Drum's decision to run a five-part article by Clive Hamilton on climate change, and to 'balance' it with five contributions from climate sceptics. Bernard Keane, of Crikey, is essentially accusing his former boss, the current editor of The Drum, of wimping out.

It's a dispute I'm not about to buy into. But there's no doubt that climate change is concentrating ABC minds. What makes the issue more complicated than most is that the degree of scepticism in the community at large bears little relation to the degree of doubt that exists in the scientific community. Those who know the most are the least dubious that anthropogenic climate change is happening, and perhaps faster than they forecast just a few years ago.

Let me digress. Richard Dawkins, well-known as a populariser of evolutionary biology, and even better known, these days, as a champion of atheism, is on a speaking tour of Australia, promoting his book The Greatest Show on Earth. It's an attempt to prove to non-scientific readers that, as Dawkins puts it, "Evolution is not a theory, it's a fact".

Like most of Dawkins's work, it's uncompromising and (at least in its opening chapter) pugilistic. But, as Dawkins told Radio National Breakfast's Fran Kelly yesterday morning,"most of the book... is enthusiastic, it's looking at the science in a very positive way... It's not an angry book".

Dawkins and Kelly went on to chat, fascinatingly, about how natural selection produced tamer wolves - with floppier ears and softer fur - before humans ever began to turn pi-dogs into Chihuahuas and Mastiffs by artificial selection; and how the nervous system of a giraffe could never have been the work of an intelligent designer. No other guest was involved.

Now, had Dawkins and Kelly been talking about his previous best-seller, The God Delusion, the executive producer of Breakfast might well have felt constrained by the need for 'balance' to include a guest who did believe in God - be that person Christian, Jewish, Islamic or even Buddhist. Even if that didn't happen, some 'balancing' interview would probably have been conducted within the next few days.

Why? Because Dawkins's atheism is controversial, and is not shared by many, perhaps most, Australians? Or because the existence of God is not a matter that can be proved or disproved by science, and therefore Dawkins's status as a respected evolutionary biologist gives his views on religion no special protection? Perhaps, a bit of both.

But RN has no plans to 'balance' yesterday's Dawkins interview by giving time in the near future to a proponent of creationism, or its more acceptable face, 'intelligent design'. It sees no need. Why not? Because creationism is espoused by rather few Australians, and therefore the ABC expects little demand for 'balance' on the topic? Or because the overwhelming scientific evidence does indeed support the 'theory' of evolution, as against intelligent design? Probably the former reason is far more important than the latter.

Suppose Dawkins were touring the United States instead of Australia. According to the most recent Gallup poll, a mere 14 per cent of Americans believe that humans evolved without the guidance or intervention of God, and 44 per cent believe humans were created by God in their present form.

Evolutionary science is no different in the United States from what it is in Britain or Australia, and indeed 74 per cent of Americans with a post-graduate degree believe in evolution by natural selection. But clearly, it would be a rash radio presenter - especially if he or she were working to editorial policies like the ABC's, which enjoin them to "present principal relevant views on matters of importance" - who ignored the fact that nearly half their listeners (and far more than that, in some parts of the country) were likely to strongly disagree with the views being proposed by Dawkins, whatever their scientific validity. The pressure to 'balance' Dawkins, at the time or shortly thereafter, by giving airtime to a proponent of creationism, would be intense.

In other words, for general programs, it's not what the boffins think, but what our listeners and viewers think, that guide our decisions about balance.

But suppose, still in the United States, we were producing a program called The Science Show. Should we still pay attention to the views of our non-scientific listeners? Or should we, as we decide what are 'the principal, relevant views', stick with what the biologists say about the science?

For sure, if the biology department of our local university were headed by an articulate advocate for 'intelligent design', we would be obliged, and indeed keen, to give him or her airtime from time to time. But we would surely have a greater obligation to make our listeners aware of what the overwhelming majority of biologists thought, and why they thought it, and to ensure that our program kept up with the latest evolutionary research.

Well, you can see where this is heading. Around 30 per cent of Australians, according to Roy Morgan Research, now say that "concerns over global warming are exaggerated". That figure has more than doubled in the past four years.

Combined with recent 'scandals' - as magnified by sceptics in the blogosphere and the popular media - concerning the University of East Anglia's CRU, and the IPCC 4th Assessment Report, and the failure of Copenhagen, it's the steadily increasing strength of sceptical views out there in the community that has ensured that ABC producers give more airtime than they might have a few years ago to sceptical views on climate change.

That is as it should be. Climate change is a vast topic, with aspects that are political, and moral, and even religious, as well as scientific. Principal relevant views clearly include those that hold that the science isn't settled, and even that global warming alarmism is a global green conspiracy.

But if I were running a science show on the ABC, I might well feel that what should guide me is the science, not shifts in popular opinion. And so far, for all the sound and fury, the vast majority of climate scientists remain convinced that the evidence for anthropogenic warming is getting stronger, not weaker, every year.

Why they think that, surely, is the really important scientific story. Isn't it? Or should I give time to dissident scientists out of all proportion to the weight of their views within the scientific community, because they reflect views held by a substantial proportion of non-scientists among my listeners?

That's an issue that pretty soon the ABC may have to tackle formally. Meanwhile, what do you think?