What US President Donald Trump says and does often flies in the face of mainstream science. Coronavirus and the idea of injecting disinfectants is only the latest episode.

When a rare solar eclipse happened in 2017, astronomers and eye doctors repeatedly warned people not to stare directly at the sun without protection. Photos show Mr Trump did anyway. He later donned protective glasses.

For decades, scientists have called climate change a pressing issue, pointing to data, physics and chemistry. Mr Trump regularly called it a hoax until recently.

He claims that noise from wind turbines – which he refers to as windmills – causes cancer, which is not accurate.

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And he has said that exercise will deplete the finite amount of energy a body has, while doctors tell people that exercise is critical to good health.

When Mr Trump wanted to defend his warning that Alabama was threatened by Hurricane Dorian last year, he displayed an official weather map that had been altered with a marker to extend the danger areas.

Alabama National Weather Service meteorologists were chastised by their agency chief when they issued tweets to reassure worried residents that they were not in the path of the hurricane.

Virus Outbreak Trump SciencePresident Donald Trump and First Lady Melania Trump wear protective glasses as they view the solar eclipse at the White House (Andrew Harnik/AP)

On Thursday, Mr Trump raised the idea of injections of disinfectant to fight the coronavirus, which health officials warned would be dangerous.

The president later claimed he was being sarcastic, although the transcript of his remarks suggests otherwise.

Mr Trump also suggested that ultraviolet light, even internal light, could be a possible preventative measure, contrary to scientific advice.

He then stated he asked the question about injecting disinfectant 'sarcastically' to the media to see 'just what would happen' after a press briefing in the Oval Office in the White House.

On Friday, as the recorded US death toll passed the 50,000 mark, the Food and Drug Administration issued an alert about the dangers of using a malaria drug that Mr Trump has repeatedly promoted for coronavirus patients.

Asked what kind of grade he would give the president on science, M Granger Morgan, a Carnegie Mellon University engineering and policy professor who has advised both Democratic and Republican administrations, answered with a quick “F”.

Nobel Prize-winning physicist Steven Chu, who was energy secretary in the Obama administration, said of Mr Trump: “When he starts to air things like that (injection), it’s definitely a danger to the public because some people might actually do that. This isn’t science. This is something else.”

“Our president certainly has high confidence in his beliefs,” added Mr Chu, chairman of the board of the American Association for the Advancement of Science, the world’s largest general scientific society. “Scientists always test their beliefs all the time. That’s part of the fabric of science.”

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Sudip Parikh, a biochemist who is chief executive of the American Association for the Advancement of Science, said Mr Trump seems to put science, medicine and controlled studies on equal footing with rumour and anecdotes.

Mixing those two up when talking to the public is “terrible for communication” and muddles and confuses the public, said Mr Parikh.

White House spokesman Judd Deere said “any suggestion that the president does not value scientific data or the important work of scientists throughout his time in office is patently false”.

He pointed to “data-driven” decisions on Covid-19, such as limiting travel from highly infected areas, expediting vaccine development and issuing social distancing guidance to slow the spread of the virus.

Mr Deere pointed to Mr Trump saying on Thursday: “My administration has partnered with leading technology companies and scientific journals to create a database of 52,000 scholarly articles on the virus that can be analysed by artificial intelligence.”

Presidents of both parties often put politics before science, and Mr Trump is not unusual there, Prof Morgan said. But this administration has regularly contradicted science and doctors.

“We’ve seen daily statements that run counter to reality, and science is about physical reality,” he said. “Science matters.”

Virus Outbreak TrumpDonald Trump claimed he was being sarcastic after raising the idea of injections of disinfectant to fight the coronavirus (Evan Vucci/AP)

Both Prof Morgan and Mr Chu said Thursday’s ultraviolet and disinfectant comments could end up harming people who do not listen to doctors.

They pointed to a case in Arizona where a couple misinterpreted Mr Trump’s promotion of a malaria drug and wrongly used related chemicals; one of them died.

Friday’s FDA warning was issued because of reports of dangerous side-effects and deaths from the use of the malaria drugs in test treatments.

Gretchen Goldman, research director for the Union of Concerned Scientists’ Centre for Science and Democracy, said the actions of Mr Trump and his administration “have ignored science, censored science, manipulated science across agencies”.

“It’s a different beef than we’ve seen in past administrations,” she said. “This administration, there’s a lot of disinterest and disrespect for science and the process.”

Her advocacy group listed 130 “attacks on science”.

Ms Goldman published a survey this week in the peer-reviewed science journal PLOS One that she and colleagues made of 3,700 federal scientists.

Half of them said political interests hinder their agencies from making science-based decisions. One in five reported political interference or censorship of some kind either from political appointees in their own agency or in the White House.

Ms Goldman said the survey, carried out in 2018 before the coronavirus outbreak, found that the highest level of scientists claiming White House interference was in the Centres for Disease Control and Prevention.

Meteorologist Ryan Maue, a conservative scholar, said that on policy, he and other conservatives like Mr Trump’s agenda of deregulation, including pulling out of the United Nations’ Paris climate agreement.

He pointed to increased funding of Nasa and its return to the moon mission as pro-science, and added that the weather service is improving its forecast models.

But when it comes to communicating science, the president “is a mess”, Maue said. “He’s trying to be funny and folksy and it doesn’t work and the media is eating that stuff up alive. And I think that’s fair.”