Former believer Paul Sheehan, in The Sydney Morning Herald yesterday, develops a new respect for informed dissent.

What I am about to write questions much of what I have written in this space, in numerous columns, over the past five years. The subject of this column is a book entitled Heaven and Earth, written by one of Australia's foremost earth scientists, Ian Plimer.

Much of what we have read about climate change, he argues, is rubbish, especially the computer modelling on which much current scientific opinion is based, which he describes as "primitive".

Plimer does not dispute the dramatic flux of climate change but he fundamentally disputes most of the assumptions and projections being made about the current causes, mostly led by atmospheric scientists.

"To reduce modern climate change to one variable, CO2, or a small proportion of one variable - human-induced CO2 - is not science. To try to predict the future based on just one variable (CO2) in extraordinarily complex natural systems is folly. Yet when astronomers have the temerity to show that climate is driven by solar activities rather than CO2 emissions, they are dismissed as dinosaurs undertaking the methods of old-fashioned science."

(He argues that) the hypothesis that human activity can create global warming is extraordinary because it is contrary to validated knowledge from solar physics, astronomy, history, archeology and geology.

"But evidence no longer matters. And any contrary work published in peer-reviewed journals is just ignored. We are told that the science on human-induced global warming is settled. Yet the claim by some scientists that the threat of human-induced global warming is 90 per cent certain (or even 99 per cent) is a figure of speech. It has no mathematical or evidential basis."

Heaven and Earth is an evidence-based attack on conformity and orthodoxy, including my own, and a reminder to respect informed dissent and beware of ideology subverting evidence.