Scientific Consensus = Scientific Truth?

Writing over at Reason, Ronald Bailey highlights the recent article in the Proceedings of the National Academy of Science which purports to rank the merit of climate scientists based on the usual metrics of articles published and articles cited. Then those scientists’ position on the anthropological global warming (AGW) hypothesis is noted. Lo and behold, skeptics tend to rank lower. The conclusion is that “good” scientists support the AGW hypothesis, while AGW skeptics tend to be more “mediocre” according to the article’s scientific rating scheme.

The “Climategate” e-mails demonstrated that the playing field is hardly level for climate skeptics, with establishment figures happy to “redefine what peer review is” in order to quash inconvenient or dissenting views. A consensus is inherently self-reinforcing, and it is hardly a surprise that those who challenge it are to some extent marginalized.

But all this analysis begs the question – does scientific consensus equal scientific truth? Bailey digs into the archives to find a few recent cases in which the scientific consensus was wrong. He finds several cases of scientific consensus in the past few decades that have now been overturned by the advance of science, including:

• belief that saccharin causes cancer,
• belief that dietary fiber prevents colon cancer, and
• confidence that nuclear fusion is just around the corner.

Bailey’s point that scientific truth is determined by testing hypotheses against the facts of reality, and not by polling scientists, is well-taken. But, I believe he missed an opportunity to talk about a couple more significant examples of scientific consensus that have been proven wrong – examples that may have more important lessons to teach us regarding the current AGW consensus.

Age of the Earth: The first example is the controversy surrounding the age of the earth. At the beginning of the twentieth century, the science of heat transfer was well established. One of the leading luminaries of physics, William Thompson (Lord Kelvin), concluded that the Earth could be no more than about 20-40 million years old, because extrapolating back in time, at the rate the Earth is losing energy it would have to have been a molten ball of rock, unable to support life. Biologists and geologists tended to favor an older Earth, consistent with Darwin’s theory of evolution, so the extent of the erroneous scientific consensus was largely confined to physicists, in this case.

Kelvin’s theory was mathematically correct, but ultimately wrong, because he did not account for the energy caused by radioactive decay. In the context of global climate modeling, critical parameters including the strength of feedback mechanisms associated with CO2 concentration, and the causal factors surrounding cloud cover fraction  and albedo are poorly understood. In analogy to the Age of the Earth controversy, it would not be surprising to discover as yet unknown feedback mechanisms that explain how the Earth has managed to remain a fairly hospitable home for life for hundreds of millions of years.

Eugenics: The “nurture” side of the “nurture versus nature” debate has been so dominant for so long that it is easy to overlook the uncomfortable prevalence of the opposite extreme in the early years of the twentieth century. Eugenics is the “science” of applying selective breeding to humans to reinforce desired traits and surpress  undesired traits. One of the pioneers of the modern eugenics movement was Sir Francis Galton who advocated that idea that character traits are genetic, and therefore those of “good breeding,” high intelligence, and high social status,  should be encouraged to procreate to increase the prevalence of their good characteristics in society, while those of “poor breeding,” low status, low intelligence, criminals, and mental defectives should be prevented from breeding. Eugenics was not a fringe movement – it had broad support from such prominent individuals as Margret Sanger, H.G. Wells, Woodrow Wilson, Theodore Roosevelt, George Bernard Shaw, John Maynard Keynes, and many others.

Eugenics supporters advocated immediate and sweeping actions to keep society from being overwhelmed by the higher birth rate of social undesirables. More than thirty states in the U.S. had compulsory sterilization for certain individuals aimed at keeping undesirables like mental patients, “imbeciles,” and criminals from polluting the genetic pool. Supreme Court Justice Oliver Wendell Holmes, Jr. writing the majority opinion in Buck v. Bell (1927) famously opined:

It is better for all the world, if instead of waiting to execute degenerate offspring for crime or to let them starve for their imbecility, society can prevent those who are manifestly unfit from continuing their kind… Three generations of imbeciles are enough.

And so the state of Virginia was allowed to sterilize Carrie Buck because of her perceived feeblemindedness. In all, some 64,000 individuals were sterilized under eugenics legislation in the U.S. When the Nazis sought precedents to justify their racial hygiene practices, they could turn to the U.S. for moral support. Stephen Gould’s The Mismeasure of Man provides a good discussion of the prevalence of eugenic beliefs as well as a rigorous debunking.

At the peak of its popularity, eugenics was a widely held scientific consensus with broad social support. It reinforced existing prejudices and racism. More competent and rigorous analysis has shown the sweeping claims of eugenics to be grossly overstated, if not completely wrong. But, eugenics led to the implementation of far-reaching policies and practices that in the fullness of time we have come to deeply regret.

Clearly, scientific consensus does not imply scientific truth. And before we enact sweeping policies to cripple our economic growth in the name of preventing global warming, we should make certain we are not repeating the mistakes of the past.