As scientists confirmed that March was the United States’ most abnormally hot month in recorded history, dozens of climate deniers gathered to promote misinformation and tout their newfound influence on federal policy.

At a conference hosted by the prominent science-denying thinktank the Heartland Institute last week, a crowd of mostly middle-aged men in suits claimed the world is finally waking up to the idea that the climate crisis does not exist.

“I feel wonderful,” James Taylor, the president of the Heartland Institute, said in an interview. “The truth is winning out.”

The clearest sign of the crowd’s rising power was the gathering’s keynote speaker: Lee Zeldin, the administrator of the Environmental Protection Agency (EPA), whom Donald Trump is also reportedly considering for attorney general. “It is a day to celebrate vindication,” he said on Wednesday morning.

In previous administrations, Zeldin said, a “cabal” of elites promoted climate science to further their agenda. Now, “we aren’t just following blind obedience to whatever the dire, doom-and-gloom prediction of the day is,” he said.

There is scientific consensus that global warming is real and urgent, and caused primarily by the burning of fossil fuels.

As people entered the event, held in the basement of a hotel near the White House, they were greeted by wares promoting climate denial.

“Good news,” read a banner outside the main ballroom, erected by the CO2 Coalition, a climate-denying non-profit that co-sponsored the conference. “There is no climate crisis.”

A table overflowed with displays reading “CO2 is a lifesaver”, pamphlets titled “Fossil fuels are the greenest energy source” and “Challenging ‘net zero’ with science”, and children’s books falsely claiming the acceleration of sea level rise is insignificant. Baskets held buttons proclaiming “Unashamed about my carbon footprint”, as well as stress balls resembling tiny Earths that read: “Don’t stress. There is no climate crisis.”

The event convened climate skeptics and outright deniers alike. While some incorrectly claimed global warming did not exist, others conceded that it was happening but falsely said it was not known to be human-caused – or an emergency.

“I believe humans have played a role in climate change. That is a far cry from saying I believe in a ‘climate crisis’,” said Taylor, the Heartland Institute president, in an emailed response to a question about the scientific consensus around global warming. “It is important not to conflate two very different assertions.”

But presenters seemed to agree on some common false themes: carbon emissions are harmless or even beneficial, renewable energy is destroying the planet, big tech and the financial sector are collaborating to undermine fossil fuels, and climate science and policy were pushed by powerful “leftist” politicians and media figures.

Naomi Oreskes, a historian of science at Harvard University who has studied climate denialism for 20 years, said rightwing thinktanks like the Heartland Institute have long painted themselves as underdogs being squashed by the elite.

“Part of the mentality of these folks is that they present themselves as victims,” she said. “Of course, that’s completely preposterous, because they’re not victims, and in fact many of these people are affiliated with very powerful groups and have been supported by Fortune 500 companies.”

She noted that the Heartland Institute has received funding from big oil companies including Shell and ExxonMobil. It has also taken contributions from the Mercers, a family of Republican mega-donors.

When the Guardian asked Taylor about where Heartland currently obtains funding, he said the question was “curious and disappointing”.

“We are funded by individuals who believe in what we advocate for: We believe in freedom, we believe in affordable energy,” he said.

In an email, Taylor said: “It has been nearly 20 years since Heartland received any money from oil companies. Even then, it was only a tiny percentage of our funding. I would gladly accept oil company funding again.”

He added that big oil “openly supports the UN climate agenda and gives far more to climate activist causes than they ever gave to Heartland”, and claimed green groups’ funding was “shady”.

With Trump in the White House, groups like the Heartland Institute, the CO2 Coalition and the Committee for a Constructive Tomorrow (CFACT) – a rightwing group which complains about “climate exaggeration” and also co-sponsored the event – are enjoying unprecedented influence.

“Twenty years ago it would have been shocking … for the EPA administrator to take seriously a group of people whose positions are so patently at odds with all of the scientific evidence,” said Oreskes. “But essentially, climate deniers are in charge now.”

During the president’s last term, a founder of the Heartland Institute met with Trump at the White House to advise him on the withdrawal from the Paris climate accord. Last year, a representative said it has “very strong affiliations” with Trump officials, DeSmog reported.

The group also contributed to Project 2025, an ultra-conservative guidebook for Trump’s second term, and the president has made good on some of the organization’s top priorities. Among them: the repeal of the “endangerment finding”, the legal determination that serves as the basis for virtually all US climate regulations. When CFACT’s president, Craig Rucker, mentioned the rollback while introducing Lee Zeldin on Wednesday, the crowd erupted in cheers.

CFACT, too, has had apparent influence on the Trump White House. Last year, the Trump administration cancelled funding for a California offshore wind project after receiving a request from the group. The CO2 Coalition’s founder also helped form a White House committee to question climate science during Trump’s first term. And last month, the group successfully nominated an ophthalmologist with no background in air pollution science to serve on a crucial air pollution committee, the New York Times reported.

Though conference attenders widely claimed their star was rising, polls indicate that the vast majority of Americans believe in climate change. That is especially true for young people, including 42% of young Republicans, according to one recent survey.

Asked about polls showing most Americans believe in the climate crisis, Taylor pointed to a 2019 survey showing most Americans were unwilling to pay even $10 per month in higher electric bills to fight global warming. “Americans lose very little sleep over global warming,” he said. But a Thursday panel, “Bringing Youth into the Climate Realist Fold”, indicated deniers have anxiety about young people’s climate concerns.

“My suggestion is to capitalize on the popularity of climate realism influencers to engineer a hashtag movement, like ‘Me Too’, but for truth,” said CO2 Coalition member Anika Sweetland, who obtained a bachelor of science in climate studies and claims to be a climate scientist, and who has little discernible presence on Instagram or TikTok. “Something like ‘hashtag fact check’ or ‘hashtag my climate wake up’.”

Another panelist, Lucy Biggers, 36, who claimed she made the Dakota Access pipeline fight at Standing Rock “go viral”, explained that she once considered herself a climate activist because she was “indoctrinated into the groupthink”.

“Young people have been so misled,” said Biggers, who serves as head of social media at the Free Press.

The youth-focused panel was disrupted by activists with Climate Defiance.

“Yo, how’s it going my fellow youths,” one disrupter, sporting a suit and a backwards hat, shouted sarcastically before being shoved out of the ballroom. “There’s no such thing as fossil fuel-caused climate change!”

In an interview, an organizer of the protest who requested anonymity for fear of retaliation said the action was intended to ensure the panel was not “allowed to go undisrupted”, especially because the panel’s audience “was almost entirely geriatric white men who will not live to see the effects of climate change the way that my generation will”.

“The message that we wanted to bring was that climate change denial is not just a matter of a difference of opinions,” said the organizer, adding that they do not believe efforts to spread climate denial to youth will be effective. “These people think that they are untouchable and that they can spread this kind of misinformation entirely unchecked? No.”