If I make an assertion that I claim to be scientific, I must be prepared to set out conditions under which my assertion can be proved false. If I tell you that my car can take you from Calgary to Edmonton on one tank of gas, I should be prepared to allow you or someone else drive it that distance and see for themselves. If my assertion is not testable, is not scientific, it is something else. The fact that the assertion may be made by a recognized “scientist’ or man of credibility is immaterial to this question. Is it is testable? Is it an hypothesis or a statement of religious conviction?
Consensus does not add up to truth. One billion falsehoods repeated one billion times do not make them true. If 500 million people fervently believe something to be true, it does not make it true. And if only one person in 6.8 billion people believe something to be true, it does not make it false. Truth is not subject to a democratic vote. For forty years the British scientific establishment stubbornly refused to entertain doubts that “Piltdown Man” was a fraud. They were determined to believe that it was indeed the missing link, despite early poignant criticisms, most notably from a German anatomist who twelve years later demonstrated that the skull of this pre-hominid consisted of the skull of a human being artificially attached to the jaw of an orangutan.
But finally the truth will out. Consensus yielded to inconvenient fact.
Anthropogenic global warming to be a credible hypothesis must be testable. True believers must at some point tell us at what point they would be prepared to admit that they were wrong. How many consecutive years of cool weather would be required? How many polar ice shelves would have to reform? How much bigger would the polar bear population have to get? It is already two to four times larger now than it was four decades ago.
We must always allot a space in our brains for doubt. A space to remain skeptical about orthodox opinions---on any subject. I accept AGW, but only provisionally and under advisement. As a multiplier of all evils, population growth must be stopped and reversed, and the necessity of that mission does not depend on the veracity of AGW theory. For public enemy Number One is biodiversity loss, and it is the inexorable spread of human monoculture that is its main cause.