Why Scientific Consensus Is Worth Taking Seriously

Yes, collective missteps happen. But if anything, history shows how hard it is to get scientists to agree in the first place.

Pretty but worrisome.

Photo by Torsten Blackwood/Pool/Getty Images

Following the pack is not part of the scientific method. The point is to follow the evidence. And that leaves room for ambiguity in interpreting the survey results showing that 97 percent of climate scientists agree that global warming is real and that human-generated greenhouse gases are a major cause. The National Academy of Sciences, American Physical Society, American Chemical Society and other relevant scientific organizations all agree, too.

For some, this consensus proves that climate change is real and that humans must take immediate action against it. But others, citing history, say the consensus view has been wrong before. Why should we believe it now? For example, scientists once believe the earth was headed into an ice age. So why should we trust them when they say the globe is warming?

A look at the history books and some chats with historians suggest scientists of the past were not the fickle flip-floppers some make them out to be. There’s nothing contradictory about short-term global warming and a much longer-term cycle of ice ages, for example.

In his book “The Discovery of Global Warming,” the historian Spencer Weart writes that in the 19th century, there was a common folk belief that God would keep a hand on the planet’s thermostat. The growing understanding that there had been long-ago ice ages shook that up, and scientists started to recognize that we might head into another ice age in thousands of years. (Recent estimates put the next one at about 50,000 years in the future.)

People did consider the possibility of global cooling on near-term timescales, too, said Harvard historian of science Naomi Oreskes. Particulate matter in smog can dim the sun enough to cool the globe. In the mid-20th century, free of the belief in God’s hand on the thermostat, scientists debated which would win out: particulate-driven cooling or greenhouse gas-driven warming. As they learned more, scientists realized the warming would dominate. The idea that there was any scientific consensus predicting an impending ice age is a lie, Oreskes said.

Another commonly cited example of the fallibility of science is continental drift. In that case, scientists get blamed for failing to accept the theory, which was proposed way back in 1912 by Alfred Wegener, and in hindsight seems sort of obvious -- just look at all those jigsaw relationships on the map. The general concept evolved, became known as plate tectonics, and finally gained widespread acceptance by the 1960s.

But between Wegener’s proposal and the 1960s, scientists held a wide range of views about what was going on with the continents, said Oreskes, who has written two books about the topic. Some thought they moved just vertically or just horizontally, or only a little. “There was debate, but no consensus,” she explained. 

Both global warming and plate tectonics were proposed decades before they became part of scientific consensus. Scientists of the early 20th century understood the possibility that coal burning would lead to greenhouse gas warming, but there wasn’t consensus until experiments showed that indeed, carbon dioxide was building up in the atmosphere, and the global temperature was rising close to the predicted rate. Likewise, Wegener didn’t know how the continents moved. Scientists eventually figured out the continents were riding around on massive “plates” of crust, the motion driven by convection of material below them.

If anything, history shows how hard it is to get a new consensus in science. Scientists have proposed plenty of wrong ideas -- from cold fusion to the connection between autism and childhood vaccines. But these are not consensus ideas. Wrong ideas that get into the heads of whole scientific communities generally don’t start with the scientists. They are part of the prevailing culture, or they represent holding places before scientists develop better theories.

Take the examples that came up a few years ago when the website The Edge posed this question to a group of scientists and other intellectuals: The flat earth and geocentric world are examples of wrong scientific beliefs that were held for long periods. Can you name your favorite example and for extra credit why it was believed to be true?

The flat earth isn’t an idea that traces back to scientists. Long before there were professional scientists, ancient philosophers realized the planet was spherical. You can get the long version of this in a good history-of-science book, such as the recent “To Explain the World” by Steven Weinberg, or a quick and dirty version on Wikipedia. To call this belief “scientific” is like calling the belief in God scientific because in pre-Darwinian times, many scientists believed in God.

The geocentric universe runs into the same problem. It’s a social belief -- a religious belief -- and it reflects the way things look from down here to those who haven’t been taught otherwise. Scientists were the ones who finally got it right. It undermines science to label past scientists as “wrong” for not knowing what hadn’t been discovered yet.

Physicists did wrongly believe in an invisible substance called “luminiferous ether” -- an idea that dates back to Aristotle and was embraced by Isaac Newton. But that was really just an extension of the status quo belief that to have a wave, you needed a substance to make the wave out of -- water, or air for sound, or ether for light. Eventually, experiments indicated the ether didn’t exist, and Einstein’s theory of special relativity showed light waves can travel through empty space. Ether wasn’t a dumb idea -- it represented an intermediate step in understanding the nature of light.

One of the more interesting wrong ideas that came up in The Edge discussion was the Great Chain of Being: a philosophical idea that stacks everything -- people, animals, plants, objects -- in a hierarchy, from lowest to highest. Charles Darwin correctly threw the Great Chain of Being into the dumpster, and proposed instead that all life sprung from a common origin and all creatures have been evolving for the same amount of time. Consensus formed around this idea because the evidence kept piling up.

Similarly, until the 20th century there was a folk belief about the climate, which Weart expresses this way in his book: “Hardly anyone imagined that human actions, so puny among the vast natural powers, could upset the balance that governed the planet as a whole … such was the public belief and scientists are members of the public, sharing most of the assumptions of their culture.” The idea of a benevolent natural balance has emotional appeal -- just as creationism did -- but if history is any guide, the smart money is on the more science-based view that replaced it.

Read more in Faye Flam’s ongoing series about the science of sorting fact from falsehood:

Science’s Weakness Is Also Its Strength
How Science Sorts Fact From Alternative Fact

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

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