Censorship of skeptic global warming views by the press has been going on for many years. This week, Paul Thornton, letters editor for the Los Angeles Times announced the paper will “no longer publish letters from climate change deniers,” as reported by Poynter.org

Thornton says, “Simply put, I do my best to keep errors of fact off the letters page; when one does run, a correction is published. … Saying ‘there’s no sign humans have caused climate change’ is not stating an opinion, it’s asserting a factual inaccuracy.” 

Really? Is this kind of censorship good public-service policy for the Los Angeles Times?

It is a good policy for the global warming alarmist movement because those who are more knowledgeable about climate change are more likely to dismiss the alarm as unfounded.

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It is not so good for citizens who would otherwise benefit from the freedom to make up their own minds after being exposed to different arguments and diverse evidence.

Is such censorship good business for newspapers and other mass media? Given that most people in the U.S. do not believe that there is a global warming problem, this seems doubtful.

One-sided coverage loses readers who do not share the editorial viewpoint.

Aristotle suggested that persuasiveness is higher when both sides of an issue are presented.

Later research found that Aristotle’s suggestion only works when one can rebut the other side.

Failing that, it is best to try to prevent the other side from being heard. 

If persuasion is the goal, and not science, then it is sensible for the warming alarmists to avoid two-sided discussions.

In our study of situations that are analogous to the current alarm over global warming, Kesten Green and I identified 26 earlier movements based on scenarios of manmade disaster (including the global cooling alarm in the 1960s). None of them were based on scientific forecasts. And yet, governments imposed costly policies in response to 23 of them.

In no case did the forecast of major harm come true.

Will it be different this time?

Isn’t it important for the public to be informed about scientific evidence on the issue? And because the alarm is based on the fear of future harm, shouldn’t the public insist on scientific forecasts?

The UN’s Intergovernmental Panel on Climate Change (IPCC) uses models that provide computer scenarios, not forecasts, of dangerous manmade global warming.

When we assessed the scenarios as if they were forecasts of what would actually happen, Kesten Green and I found that they violated 72 of 89 relevant scientific forecasting principles.

Would you go ahead with your flight, if you overheard two of the ground crew discussing how the pilot had skipped 80 percent of the pre-flight safety checklist? 

For rational policy-making and regulating, scientific forecasts are necessary.

We are astonished that there is only one published peer-reviewed paper that claims to provide scientific forecasts of long-range global mean temperatures. The paper is a 2009 article in the International Journal of Forecasting by Kesten Green, Willie Soon, and me.

When we tested our forecasts against the IPCC scenarios using data from 1850 to the present, our forecasts, based on a model that adhered to scientific principles, were more accurate over all forecast horizons from 1 to 100 years.

They were especially more accurate for long-term forecasts.

For example for forecasts 91 to 100 years ahead, the IPCC forecast errors were over 12 times larger than our forecast errors. Perhaps that qualifies as relevant evidence for citizens. And it would be “news” for 99% of them. Yet our forecasts received virtually no mass media coverage. Meanwhile, non-scientific climate-scare “forecasts” regularly get widespread attention from the mass media.

Want to bet which forecast of global mean temperatures is going to be correct? Mr. Gore did not want to bet against me in 2007 when he was warning that the world was at a climate “tipping point.” That was wise decision on his part. Scientific forecasting methods tend to be more accurate than political forecasting methods.

Fortunately, with many mass media outlets attempting to influence people by using censorship, citizens are able turn to alternative sources of information and argument on the Internet to inform their decisions. And many have. The polls provide evidence that the alarmist case is so weak that even with widespread censorship, citizens are not persuaded.

Professor J. Scott Armstrong teaches at the Wharton School of Business at the University of Pennsylvania in Philadelphia. He is a founder of the two major journals on forecasting methods, author of Long-Range Forecasting, editor of the Principles of Forecasting handbook, and founder of forecastingprinciples.com. He is the world's most highly cited author on forecasting methods. He has been doing research on forecasting methods for over half a century. Fox News was the first to cover the bet that he proposed to Mr. Albert Gore in 2007 (see theclimatebet.com for the latest results).