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Matt Ridley is the author of provocative books on evolution, genetics and society. His books have sold over a million copies, been translated into thirty languages, and have won several awards.

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Testing past consensi

Previous declarations of scientific consensus have often proved wrong

Update: apologies for formatting problems in a previous version of this blog post.

Last week a study claimed that 97-98 percent of the most published climate scientists agree with the scientific consensus that man-made climate change is happening.

Well, duh. Of course they would: it's their livelihood. Anyway, so do I. So do most `sceptics': they just argue about how much and through what means. You can believe in man-made carbon dioxide causing man-made climate change but not in net positive feedbacks so you think the change will be mild, slow, hard to discern among natural changes and far less likely to cause harm than carbon-rationing policies: that's still within the range of possibilities of the IPCC consensus.

Besides, what happened to previous declarations of certain scientific consensus? In Reason magazineRon Bailey has gone back and looked up the phrase in the mainstream media before 1985. He finds that it was used about a whole bunch of assertions that later proved false, exaggerated or misleading

First saccharin:

One of the first instances of the uses of the phrase appears in the July 1, 1979 issue of TheWashington Poston the safety of the artificial sweetener saccharin. "The real issue raised by saccharin is not whether it causes cancer (there is now a broad scientific consensus that it does)"

Yet

Thirty years later, the National Cancer Institute reportsthat "there is no clear evidence that saccharin causes cancer in humans.

Second dietary cancer:

Similarly, the Postreported later that same year (October 6, 1979) a "profound shift" in the prevailing scientific consensus about the causes of cancer. According to thePost, researchers in the 1960s believed that most cancers were caused by viruses, but now diet was considered the far more important factor. One of the more important findings was that increased dietary fiber appeared to reduce significantly the incidence of colon cancer.

Yet

Twenty years later, a major prospective studyof nearly 90,000 women reported, "No significant association between fiber intake and the risk of colorectal adenoma was found." In 2005, another big study confirmedthat "high dietary fiber intake was not associated with a reduced risk of colorectal cancer."

Third, fusion:

The December 17, 1979 issue of Newsweekreported that the Department of Energy was boosting research spending on fusion energy reactors based on a scientific consensus that the break-even point-that a fusion reactor would produce more energy than it consumes-could be passed within five years.

Yet

That hasn't happened yet and the latest effort to spark a fusion energy revolution, the International Thermonuclear Experimental Reactor, will not be ready for full-scale testing until 2026.

Fourth, acid rain:

The March 10, 1985 New York Timescited environmental lawyer Richard Ottinger, who asserted that there is a "broad scientific consensus'' that acid rain is destroying lakes and forests and ''is a threat to our health.''

Yet

The [official] assessment concluded that acid rain was not damaging forests, did not hurt crops, and caused no measurable health problems. The report also concluded that acid rain helped acidify only a fraction of Northeastern lakes and that the number of acid lakes had not increased since 1980.

Had he been able to go back further in time, Bailey would have found just as firm a scientific consensus behind eugenics.

Of course, some assessments are right. And of course, the environmentalists most loudly proclaiming that we must obey the scientific consensus on climate change take no such notice of the consensus that genetically modified crops are safe.