John Cook has spent the past decade studying the psychology of climate denialists and the past few months trying to understand their ideological cousins: people who scoff at the coronavirus.

Mr. Cook, a research assistant professor at the Center for Climate Change Communication at George Mason University and founder of the Skeptical Science, a website that debunks common arguments by climate change deniers, said the parallels between the two groups are striking. In both cases, he said, being confronted with technical facts appears to have little effect.

“Ideology is a big predictor of people’s attitudes about climate change, but tribalism is even more so,” he said. “Ultimately humans are social animals. If my tribe believes that climate change is a hoax, I’m much more likely to believe that. And that’s definitely also at play with Covid.”

That means, on both issues, leadership is crucial to changing attitudes and conquering denial.

That doesn’t appear to be happening, for now, at least. President Trump has long dismissed climate change as a hoax and worked to roll back environmental regulations. And, rather than urge people to take coronavirus seriously after being infected himself, Mr. Trump removed his mask as soon as he returned to the White House on Monday night and infuriated medical experts by telling supporters “don’t be afraid” of Covid-19.

A recent Cornell University study found Mr. Trump was one of the leading sources of coronavirus misinformation in the early months of the pandemic.

The White House has said Mr. Trump takes the health of his staff and the American public seriously and incorporates Centers for Disease Control and Prevention guidelines and best practices for limiting exposure to the coronavirus.

Mr. Cook noted that when it comes to climate change, however, fewer than 10 percent of Americans are outright dismissive of the science. About 12 percent of the public are also “not at all” concerned about coronavirus.

This means, he said, the solution lies not in persuading those already steeped in science denial, but in inoculating the other 90 percent of the public from scientific disinformation.

He likened the challenge to eradicating polio — an incurable disease that was all but eliminated in the United States through vaccinations. In the case of climate and Covid, he said, that means using facts and research, combined with vivid analogies, to explain the techniques used to mislead the public.

For example, Mr. Cook said, reminding people that a cold snap disproves climate change about as much as being full after a big meal disproves the existence of global hunger.

“The power of those analogies is that it takes what can be abstract and roots it in everyday life experience,” he said.

Still, Mr. Cook said, cues from political leaders remain one of the biggest drivers of public opinion. “It would take something big to change the dismissiveness,” he said. “It would take Republican leadership and the president to come out and lead them.”