Chris de Freitas who died this week will be missed. I don't know whether he was the only scientist in the school of environment at the University of Auckland who doubted we are destined for catastrophic climate change but he was the only one who had the courage to say so in public.

If he was alone his courage was all the greater.

It must be hard, and I suspect career threatening, to disagree with the received wisdom in any academic discipline. That word discipline is used because advanced academic thinking is supposed to be built on the studies and conclusions of others that are accepted in the field, which is one reason why their writing contains so many extraneous references.

The other reason is that an academic career is assisted by references in the work of colleagues and you wouldn't want to put yourself outside the college.

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I never met de Freitas, I knew him only as an occasional contributor to the opinion pages of this paper. I thought his views on climate change always worth reading not just because they disagreed with the scientific consensus but because they were calmly and dispassionately argued, a rare quality on both sides of this debate.

De Freitas held the view that climate change could not be reliably predicted from computer models which are only as good as the data they are fed, and he believed the standard predictions were based on excessive assumptions of acceleration in the accumulation of carbon dioxide in the atmosphere. There was no debate, he said, that burning fossil fuels is adding to the build up.

"But the degree of global warming directly caused by the extra carbon dioxide is, by itself, relatively small. This is not controversial. What is controversial is whether this initial change will trigger further climate changes that would be large or damaging. Debate focuses on climate feedbacks that may or may not suppress, perpetuate or amplify an initial change caused by increasing concentrations of greenhouse gases."

He said, "Computer climate models project more warming because the modellers build in feedbacks from water vapour and clouds that amplify the initial change. These are the so-called positive feedbacks. For example, higher temperature would mean more evaporation globally, which in turn means more heat-trapping water vapour is put into the atmosphere leading to even higher temperatures. On the other hand, negative feedbacks might prevail. For example, more water vapour in the atmosphere could lead to greater cloud cover. Clouds reflect the heat from the Sun and cool the Earth, offsetting the initial rise in global temperature ..."

That was written six years ago and for all I know the net effect of clouds may be settled to the satisfaction of the science now, but in his last piece in the Herald, published a year ago, de Freitas wrote, "Recent research findings show there is no evidence - none at all - to support the global warmers' scaremongering." That was unusually intemperate for him.

He was responding to a column by sociologist Jarrod Gilbert who called scepticism on climate change a crime against the future.

"What is happening to our education system when university lecturers attack, rather than defend, free speech?" de Freitas asked.

"Just as sceptics have no right to ridicule what is a potentially serious topic, climate catastrophists have a social responsibility not to unjustifiably spook the public." He finished, "One could reasonably argue that lack of evidence, one way or the other, is no reason for complacency. I will concede that."

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Google the name Chris de Freitas and you will find tracts of condemnation from non-scientists, journalists I suspect, who typically start by declaring they haven't space to explain why he is wrong and proceed to compile a long indictment of his writing, teaching and course material. They are aghast he would say there is no evidence for scaremongering and condemn him in the tone and internal logic of a Stalinist show trial.

Like most people who are not qualified to argue with the consensus, I accept it without finding myself moved to do much about it. I don't think accepting the science means we must act as the scientists advise. I don't take all of my doctor's advice. I reserve the right to enjoy life at a possible cost to my future health.

Climate alarmists will point out that refusing to act on their advice for containing climate change endangers not my life but that of future generations so I agree, something needs to be done. It has to be done by the world, not individual countries. Trump's withdrawal from the Paris agreement was among the dumbest things he has done.

Ironically, it may have stiffened the resolve of responsible leaders to do something about it. I wonder what Chris de Freitas thought.