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Is there really a consensus? What does that mean, anyway?

We're frequently told the global warming debate is over because a "scientific consensus" exists. Does this mean that all scientists of any stature believe the planet is in peril? Actually, vigorous debate continues. Smart people with impressive credentials can be found on all sides of this question.

Freeman Dyson, one of the finest scientific minds of our time, disagrees with much of the global warming thesis. A petition rejecting global warming has attracted the signatures of 31,000 Americans with science degrees - including 9,000 with PhDs. A partial list of international scientists who dissent from global warming theory has its own Wikipedia page.

If "consensus" means that a majority of the world's scientists believe in global warming - that's probably true. It's also true that prominent science journals and international scientific bodies have endorsed the concept.

But scientific validity isn't determined by majority vote. It was Galileo - not the consensus of his time - who had it right. When French researcher Pierre Louis concluded, in the early 1800s, that bloodletting was of limited use in treating pneumonia, he was challenging 2,000 years of standard medical practice.

Freeman Dyson: 'In the history of science it has often happened that the majority was wrong and refused to listen to a minority that later turned out to be right.'

Albert Einstein said: "The important thing is not to stop questioning." So why do so many people insist the science is beyond dispute and that there's nothing further to discuss?

Reason 1: People who believe they're saving the planet can be impatient. Because they feel a sense of urgency, ongoing debate seems pointless to them. They're interested in action, not more talk.

But if the diagnosis is wrong, taking action may harm the situation rather than help it. Reasonable people acknowledge other points-of-view and give everyone the opportunity to hear all sides.

Reason 2: We trust experts. When we're told the world's leading experts in a particular field have examined matters carefully and agree there's cause for alarm, it's perfectly understandable that we take their word for it. Ordinary people behave this way. So do scientists in other fields. And so do journalists.

Reason 3: We believe journalists. Much of what we know about global warming was written by journalists - most of whom took few, if any, college-level science courses. They don't understand complicated scientific matters any better than the average person.

Additionally, journalists often rush to meet deadlines. Reporters rarely have time to read more than the summary of any scientific report. In the case of global warming, that's a critical fact to keep in mind.



[last edit: May 2010]

>> Jay Richards' excellent discussion of consensus in a scientific context
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>> This Is not fair play (2-minute YouTube video)
>> On saying the debate is over (2 minute YouTube video)
>> Recommended reading