Scientists are worried about the Trump administration: His pick for the Environmental Protection Agency doesn’t seem interested in protecting the environment, his energy secretary lacks the publication record of his highly academic predecessors and the president himself once tweeted that global warming is a Chinese hoax. In light of such issues, they’re planning a march to advocate the use of scientific evidence in political decision-making.

Was there ever an alternative to evidence? Most policymakers already believe that their decisions are firmly rooted in science. The best science. Problem is, it’s often hard to distinguish between fact-based scientific evidence and marketing material. It’s not even clear that the Science March organizers have a very good understanding of the issue. One of their tweets (since deleted) read: “colonization, racism, immigration, native rights, sexism, ableism, queer-, trans-, intersex-phobia, & econ justice are scientific issues — March for Science (@ScienceMarchDC) Jan. 29, 2017”

Along with a march, maybe we need better education on the difference between science and politicized pseudoscience.

The march is scheduled for April 22 — Earth Day, which has its own history in faulty science. The first Earth Day, in 1970, was not so much a celebration of the planet as a premature obituary for the human race. Researchers predicted that humans would soon deplete the world’s natural resources and wipe themselves off the planet. Stanford University biologist Paul Ehrlich predicted that between 1980 and 1989, 4 billion people, including 65 million Americans, would starve to death. Nobel laureate George Wald estimated that civilization would end within 15 or 30 years unless humans took immediate action. Life magazine ran a terrifying cover story saying that “scientists have solid experimental and theoretical evidence” to predict that “by 1985 air pollution will have reduced the amount of sunlight reaching Earth by one-half,” and “increased carbon dioxide in the atmosphere will affect the Earth’s temperature, leading to mass flooding or a new ice age.”

It was more hype than science. None of the predictions had testable hypotheses. They simply coupled historical population growth rates with an absurd doomsday model. Ridiculous as the claims were, no one really wanted to refute them or argue against the conservation of natural resources. Apocalyptic warnings could be used to further any political agenda, including government funding for researchers, contraceptive subsidies and immigration restrictions.

Evidence-based research can also be abused. By the 1950s, researchers had shown a strong causal link between smoking and lung cancer. A 1964 U.S. study found that lung cancer accounted for 3.3 percent of 15,238 deaths among smokers, and only 0.9 percent of 3,726 deaths among non-smokers — pretty strong evidence that smokers run a higher risk. Representatives of the tobacco industry, however, pointed to the same numbers and concluded that there’s no link, because 97 percent of smokers didn’t die of lung cancer.

Oil companies use a similar tactic. Industry-sponsored climate skeptics like to cite the uncertainties in climate change models as evidence that the science is inconclusive. Scientists might not have perfect information about volcanic emissions or the impact of clouds, but models of complex phenomena always entail uncertainties. They don’t need to be exact in every respect to communicate information about a dangerous directional trend, and the presence of confidence intervals doesn’t mean that climate change is a matter of opinion.

Misrepresentation happens in every industry: nuclear weapons, genetically modified foods, vaccination, fat consumption, sugar consumption, drug safety, recreational drug safety. Scientists tend to think that observable facts lead to universally rational decisions, but that’s rarely the case. Public policy is complicated, and the goal of scientific research isn’t to guarantee an outcome; it’s to inform the best possible thinking about certain aspects of the world.

So if marchers really want to support science, they should leave their political agendas at home.

Elaine Ou is a blockchain engineer at Global Financial Access, a financial technology company in San Francisco. Previously she was a lecturer in the electrical and information engineering department at the University of Sydney.

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