Warming was a recurring natural phenomenon and had been observed on other planets, including Mars, Jupiter, Pluto and Neptune, the four backbenchers said in a dissenting chapter in a parliamentary report related to climate change.

"It is the natural property of planets with fluid envelopes to have variability in climate. Thus, at any given time, we may expect about half the planets to be warming. This has nothing to do with human activities," they wrote.

The fact that climate change had been observed on other planets and on Triton, Neptune's largest moon, was a problem for the view that man-made greenhouse gases had caused global warming on Earth, they said.

Climate change believers, including media tycoon Rupert Murdoch, often formed their environmental views without due knowledge, they added.

"This exemplifies the more general problem that most of the public statements that promote the dangerous human warming scare are made from a position of ignorance," they wrote.

The four backbenchers are all members of Prime Minister John Howard's coalition government and included two former ministers.

Howard distanced himself from the four. "No, I don't agree with their views," he said when asked about their statement about Rupert Murdoch.

The prime minister was previously a global warming sceptic but has since accepted majority scientific opinion that the emission of greenhouse gases is heating up the planet.

Former rock star Peter Garrett, now the environment spokesman for the opposition Labor party, asked Howard which planet the backbenchers were on after the report triggered a debate in parliament.

The four included former ministers Jackie Kelly and Danna Vale, former research scientist Dennis Jensen and David Tollner, a legislator from the rugged Northern Territory.

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