Six years ago, the UN Intergovernmental Panel on Climate Change was 90 per cent certain that human activity was the main cause of climate change. That percentage has since risen to 95, according to a new draft report leaked last week. Try as climate deniers might, they can't hide from the science forever, writes Clive Hamilton.

The IPCC's Fifth Assessment Report, predictably leaked last week, will not make any significant difference to the global debate. Further confirmation of the science will certainly not persuade any climate science deniers. They are beyond persuasion, because the argument is only superficially about the science. It's really about culture and ideology.

While dogmatic in their rejection of science, climate deniers are happy to cover all bases. First, they deny that climate change is occurring. Then they say that if it is occurring it's not due to humans. Then they claim that if it is due to humans, the effects are trivial. If the effects are shown to be non-trivial, they opine that the benefits will exceed the damage. If the damage is shown to predominate, they say the cost of avoiding the damage is too high.

One can never win an argument against a climate science denier. Plenty have tried, but when the pressure of logic becomes too great they just revert to the same old slogans, often borrowed from the opinion pages of the Murdoch press. Nick Minchin is a master of it.

While it would be reassuring to believe that the weird logic and contempt for evidence circulate only in the bubble of climate denial, the truth is that it has a much wider impact in the community, that is, among those 80 per cent or more of Australians who, when asked by pollsters, say they 'believe in climate change'.

The standard denialist factoids and arguments (mostly imported from America) pop out in everyday conversations with otherwise sensible people. You can see why. Who wants to take on the full implications of the warnings of the world's climate scientists, even if human-induced global warming is now so well founded using multiple lines of evidence that it is as near to a consensus as is possible in any field of scientific endeavour?

I have been in rooms where even sophisticated people who would cringe at being associated with climate deniers look for comfortable ways out. They pull back from what the science requires because the policy task looks too hard, oblivious to the fact that it now looks harder because others before them have reacted with the same timidity.

The point is that politicians instinctively know all of this. They know that most Australians accept the science and are at times worried about climate change. They want their governments to 'do something' and make the problem go away.

Yet our political leaders also know, from street talk, focus groups and hard political experience, that Australians want symbolic actions only, actions that will make them feel better about themselves but not require anything of them. When political leaders get it wrong, and take what voters tell pollsters at face value, they find themselves in hot water.

This is the only plausible explanation for the extraordinary and confusing gyrations in climate policy over the last eight years. Several leaders have been ditched because they have been unable to get the nuances right. (I use 'leaders' advisedly, for the situation will only be resolved by real leadership that forces Australians to man up.)

When Julia Gillard said 'I believe in climate change' we knew that she did not get it at all. We don't 'believe in' the laws of physics; we accept the science or we don't. When Kevin Rudd said climate change is the 'greatest moral challenge' I think he really meant it, until it became convenient to regard it more as a bit of a moral challenge.

Tony Abbott is more honest. He does not believe in climate change, and we all know that he does not. He is using the world's most audible dog-whistle. When he becomes prime minister he will appoint charlatans to senior positions to advise and oversee climate policy (which, because the stench will spread, will bring all Australian science into disrepute).

Mr Abbott knows he cannot publicly repudiate climate science and repeal all policies because the Australian public's demand to be seen to be doing something must be satisfied. That is why he can put forward his Direct Action Policy, a policy that is so absurd that no respectable policy wonk would have anything to do with it. Compared to the alternatives, it will be much less effective, much more expensive and will ask taxpayers who pollute a little to pay to reduce the emissions of those who pollute a lot.

But for Tony Abbott, none of that matters. He wants a do-nothing policy for a non-problem; after all, an 'invisible substance' can do you no harm.

The true hypocrisy lies not with Tony Abbott but with Greg Hunt, who accepts the science but promotes a scheme he knows will not work because he yearns more to be a minister than to protect the world his grandchildren will inherit. The same criticism can be levelled at Malcolm Turnbull and Julie Bishop, and long-term handwringers like Mal Washer, who are campaigning for the end of effective climate policy.

Yet despite all of this, one thing seems certain: Tony Abbott too will be killed off by climate change. His hero, John Howard, found that Australians could not be fobbed off for long with non-policies. And the relentless march of science, not to mention disruption to the world's weather, will weigh more and more heavily on the conscience of the great Australian voter.

Clive Hamilton is Professor of Public Ethics at Charles Sturt University in Canberra, and is currently a visiting academic at University College London. He is a member of the Australian Greens. View his full profile here.