Archbishop of Sydney George Pell, a shrewd cleric who knows a dodgy millennial cult when he sees one, has persisted in his long-held critique despite the climate change alarmism of his brother bishops.

Even Don Aitkin, former vice-chancellor of the University of Canberra, whom I'd previously been tempted to write off as a slave to political correctness, outed himself the other day as a thoroughgoing sceptic.

The latest countercultural contribution came in The Australian on Wednesday. Phil Chapman is a geophysicist and the first Australian to become a NASA astronaut. He makes the standard argument that the average temperature on earth has remained steady or slowly declined during the past decade, despite the continued increase in the atmospheric concentration of carbon dioxide, with a new twist.

As of last year, the global temperature is falling precipitously. All four of the agencies that track global temperatures (Hadley, NASA Goddard, the Christy group and Remote Sensing Systems) report that it cooled by about 0.7C in 2007.

Chapman comments: "This is the fastest temperature change in the instrumental record and it puts us back where we were in 1930. If the temperature does not soon recover, we will have to conclude that global warming is over. It is time to put aside the global warming dogma, at least to begin contingency planning about what to do if we are moving into another little ice age, similar to the one that lasted from 1100 to 1850."

A little ice age would be "much more harmful than anything warming may do", but still benign by comparison with the severe glaciation that for the past several million years has almost always blighted theplanet.

The Holocene, the warm interglacial period we've been enjoying through the past 11,000 years, has lasted longer than normal and is due to come to an end. When it does, glaciation can occur quite quickly. For most of Europe and North America to be buried under a layer of ice, eventually growing to a thickness of about 1.5km, the required decline in global temperature is about 12C and it can happen in as little as 20 years.

Chapman says: "The next descent into an ice age is inevitable but may not happen for another 1000 years. On the other hand, it must be noted that the cooling in 2007 was even faster than in typical glacial transitions. If it continued for 20 years, the temperature would be 14C cooler in 2027. By then, most of the advanced nations would have ceased to exist, vanishing under the ice, and the rest of the world would be faced with a catastrophe beyond imagining. Australia may escape total annihilation but would surely be overrun by millions of refugees."

Chapman canvases strategies that may just conceivably prevent or at least delay the transition to severe glaciation. One involves a vast bulldozing program to dirty and darken the snowfields in Canada and Siberia, "in the hope of reducing reflectance so as to absorb more warmth from the sun. We may also be able to release enormous floods of methane (a potent greenhouse gas) from the hydrates under the Arctic permafrost and on the continental shelves, perhaps using nuclear weapons to destabilise the deposits".

He concludes: "All those urging action to curb global warming need to take off the blinkers and give some thought to what we should do if we are facing global cooling instead. It will be difficult for people to face the truth when their reputations, careers, government grants or hopes for social change depend on global warming, but the fate of civilisation may be at stake."

The 10-year plateau in global temperatures since 1998 has already sunk the hypothesis that anthropogenic greenhouse gas will lead to catastrophic global warming. To minds open to the evidence, it has been a collapsing paradigm for quite some time.

But Chapman's argument about last year's 0.7C fall being "the fastest temperature change in the instrumental record" ups the stakes considerably.

It replaces an irrational panic in the public imagination with a countervailing and more plausible cause for concern. It also raises, more pointedly than before, a fascinating question: since there are painful truths with profound implications for public policy to be confronted, how will the political class manage the necessary climb-down?

In Australia, Rudd Labor's political legitimacy is inextricably linked to its stance on climate change. If the Prime Minister wants a second term, he'll probably have to start "nuancing his position", as the spin doctors say, and soon.

A variation on J.M. Keynes's line - "when the facts change, I change my mind" - admitting that the science is far from settled and awaiting further advice, would buy him time without necessarily damaging his credibility.

Taking an early stand in enlightening public opinion would be a more impressive act of leadership. While obviously not without risk and downside, it would make a virtue out of impending necessity and establish him, in Charles de Gaulle's phrase, as a serious man.

I don't think he's got it in him. But we can at least expect that some of the more ruinously expensive policies related to global warming will be notionally deferred and quietly shelved. Innovation, Industry, Science and Research Minister Kim Carr will be allowed to invest in high-profile nonsense such as funding "the green car".

But the coal industry is unlikely to be closed down or put into a holding pattern. Nor are new local coal-fired power stations going to be prohibited until the technology is developed to capture and sequester carbon.

Since the greater part of the funds for the research underpinning that technology is expected to come from the private sector - and there's a limit to what government can exact by administrative fiat - as the debate becomes calmer and more evidence-based, business will be increasingly reluctant to outlay money on a phantom problem.

Budgetary constraints and rampant inflation provide governments with plenty of excuses for doing as little as possible until a new and better informed consensus emerges on climate.