Steve Fielding has had a conversion that could blow apart the great global warming scare.

No wonder the Rudd Government is scrambling and the ABC is already sliming the Family First senator.

You see, Fielding has suddenly realised that global warming may not be caused by humans after all.

What has startled him out of merely accepting we're heating the world to hell with our carbon dioxide emissions is one fact in particular.

While our emissions are increasing fast each year, satellite measurements show the world's temperatures have still not risen above the 1998 record, and have actually fallen since 2002.

Of course, all this has been pointed out before. I've asked both Prime Minister Kevin Rudd and Climate Change Minister Penny Wong - to their faces - to explain why the world isn't still warming as it should if their global warming theories are right.

Neither has given me an answer. Nor have they answered similar challenges from the few sceptics in Parliament who have dared to reveal themselves - notably the Nationals' Barnaby Joyce and the Liberals' Dennis Jensen.

But here's why Fielding's conversion is potentially so much more dangerous to the Government than sniping from mere columnists or Coalition MPs.

Fielding is not just in a position to ask the Government the same question. He can also demand a straight answer.

If he does not get it, his vote in the Senate could destroy the Rudd Government's plan to impose billions of dollars of taxes on all our sources of emissions - from power stations and smelters to, eventually, even cows.

With the Liberals refusing to back the scheme this year, the Government needs not just the votes of the Greens but of the two crossbench senators, Nick Xenophon . . . and Fielding.

But Fielding, an engineer, is now insisting he be shown the proof that the world is even still warming, and the Government must at last justify its plan's most basic assumption.

Five days ago, in the US, he put this very question to Joseph Aldy, President Barack Obama's special assistant on energy and the environment, and is yet to get the answer he's been promised.

Now he'll sit down with Wong - probably within the week - and ask again: Why is the world still not warming when our emissions are increasing?

See the Government now frantically wondering how to answer. Climate Change Assistant Minister Greg Combet yesterday would not even say if he'd allow Fielding to consult Government scientists.

Amazing. Is science now so political that its findings must be restricted?

Yet perhaps the strangest thing about Fielding's conversion is his confession:

"Until recently I, like most Australians, simply accepted without question the notion that global warming was a result of increased carbon emissions."

How is it that even a politician did not know until someone the other day thrust graphs into his hand that thousands of scientists doubt man is warming the world?

Or that the warming has paused this decade?

The ABC's treatment of Fielding since he announced his new position explains perhaps why such information isn't getting out, and why so many sceptics do not dare speak.

Take Fielding's interview on Jon Faine's ABC 774 program yesterday.

Faine refused to ask about the problems in the warming theory that had made Fielding demand answers.

Instead he asked angrily whether Fielding's "religious approach" was messing with his thinking, and whether we could take seriously a Christian who allegedly believed in "creation science".

Wasn't Fielding just "positioning himself" for more political clout, and why would he not just give the planet the "benefit of the doubt".

Faine insisted, without evidence, that just a handful of scientists were sceptics, and even libelled an Australian one, Prof Bob Carter, suggesting he was just a "gun for hire" - a man who'd say what he was paid to.

Immediately afterwards, Faine interviewed (gently) a climate alarmist who claimed Fielding was the kind of patsy who'd say smoking didn't kill.

Debate? This is more like a religious war, with heretics to be burned, not reasoned with.

Except for this: Fielding has his priceless vote, and for once we have someone who must be answered. Has the world stopped warming? And why?