Chris de Freitas is an associate professor in the School of Environment at the University of Auckland.

The column by University of Canterbury sociologist Jarrod Gilbert describing climate change "denial" as a crime, is alarming because he suggests those with opinions different to his should be silenced. What is happening to our education system when university lecturers attack, rather than defend, free speech?

The most worrying aspect of this is the apparent desire to close down debate on a theme that is associated with costly energy policies and other grave economic consequences.

Calling climate sceptics "deniers" is done with the intention of putting them in the same class as "Holocaust deniers". In this context, "denier" has much the same connotation as the N word to refer to people of a certain skin colour. Such insinuations are an insult to those who suffered and died in the Holocaust or those with dark skin. It is both inappropriate and offensive.

In the words of colleague Benny J. Peiser: "As long as we are unable to explain the evident inconsistencies that fly in the face of climate alarmism, attempts to associate scientific scepticism with Holocaust denial can only be regarded as political incitement."


The level of hysteria now being stirred up against climate scientists who are raising very serious questions is reminiscent of attacks made on scientists in Stalin's Soviet Union and pre-war Germany. Those who resort to shooting at the messenger are presumably those without solid arguments on the science.

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.

Climate change scepticism comes in many forms, some which are no less absurd than climate catastrophism. No sceptic denies that climate changes. There is no such thing as a constant climate. For 4.2 billion years, climate has always been getting warmer or colder, wetter or drier, and there has never been runaway warming or cooling.

Recent research findings show there is no evidence -- none at all -- to support the global warmers' scaremongering.

Most climate scientists would agree rising carbon dioxide in the atmosphere due to fossil fuel use could affect global climate. Basic physics supports this view. But there is no evidence that the putative change would be large or damaging. Output from computer models is not evidence unless model performance has been validated. So far, it has not.

For significant global warming to occur, increased concentrations must set in motion positive (or destabilising) feedback processes. Such processes would cause temperatures to rise by some other mechanism. One such mechanism is increased evaporation caused by higher temperatures leading to rising water vapour concentration, which is by far the most important greenhouse gas. This would increase retention of energy from the Sun and lead to further warming.

To date, scientific evidence suggests that negative (stabilising) feedback processes prevail, possibly due to the cooling effect of increased cloudiness from water vapour increase. If true, this means it is unlikely higher concentrations of carbon dioxide in the atmosphere will greatly influence global climate.

Negative feedback processes are played down by climate alarmists who assume climate is governed by positive feedback processes which they claim will lead to runaway global warming. Four billion years of global climate history shows that negative feedbacks prevail.

"Climate change" does not confirm that carbon dioxide is causing it. The evidence would have to distinguish between human-caused and natural change. This has not been done.

From the research to date, it appears the influence of increasing carbon dioxide on global warming is almost indiscernible. Warming could occur, but no evidence suggests it will amount to much.

One could reasonably argue that lack of evidence, one way or the other, is no reason for complacency. I will concede that.