Scientists overwhelmingly agree that humans are contributing to global warming in a significant way: 97 per cent of tens of thousands of scientists from a variety of disciplines are convinced of anthropogenic global warming (AGW).
But consensus alone doesn’t make it true. Albert Einstein make that point in 1931 when a book was published renouncing his theory of relativity. The title, “100 Authors against Einstein,” said it all.
Einstein replied: “Why 100? If I were wrong, one would have been enough.” His point was that consensus does make a scientific fact. He wasn’t right just because he was Einstein. He was right because thousands of scientists found that he was right.
Revolutionary ideas aren’t necessarily true but many are. Michael Shermer, publisher of Skeptic magazine, lists some:
“The Copernican model, germ theory, the vaccination principle, evolutionary theory, plate tectonics and the big bang theory were all once heretical ideas that became consensus science. How did this happen?”
It didn’t become true based on the results of a poll. The results of a poll done in 2011 by Associated Press-GfK showed 77 per cent American adults believe in angels.
By the consensus model alone, angels exist. Both the majority scientists who believe in AGW and the believers in angels must be right. However, if we apply the test of consilience, one belief tumbles. Consilience is defined as the linking together of principles from different disciplines to form one comprehensive theory.
The 19th-century philosopher of science William Whewell argued for a “consilience of inductions.” Inductive reasoning is defined as that which derives general principles from specific observations.
“For a theory to be accepted, Whewell argued, it must be based on more than one induction—or one single generalization drawn from specific facts,” explains Shermer. “It must have multiple inductions that converge on one another, independently but in conjunction.” Call it a convergence of evidence.
Whewell wrote in his 1840 book: “Accordingly the cases, in which inductions from classes of facts altogether different have thus jumped together, they belong only to the best established theories which the history of science contains.”
The flaw in the belief of angels is that inductive reasoning isn’t used, let alone the more rigorous test of consilience. To meet the standard of consilience for angels, not just one generalization from many facts must come about, but many generalizations must come together.
One the other hand, it’s not difficult to study whether climate change is caused by humans. That’s because there is a convergence of evidence from multiple lines of inquiry—pollen, tree rings, ice cores, corals, glacial and polar ice-cap melt, sea-level rise, ecological shifts, carbon dioxide increases, the unprecedented rate of temperature increase—that all converge to a singular conclusion.
So, what about the three per cent of scientists who don’t believe in AGW? Perhaps they, being in the minority like Einstein was, are right. But they fail the test of consilience and have a number of flaws including cherry-picking, curve-fitting, and disregard for inconvenient data.
“That is, instead of the 3 percent of papers converging to a better explanation than that provided by the 97 percent, they failed to converge to anything,” says Shermer.