This story originally appeared on Mother Jones and is part of the Climate Desk collaboration.

Google, Facebook, and Microsoft have publicly acknowledged the dangers of global warming, but last week they all sponsored a conference that promoted climate change denial to young libertarians.

All three tech companies were sponsors of LibertyCon, the annual convention of the libertarian group Students for Liberty, which took place in Washington, DC. Google was a platinum sponsor, ponying up $25,000, and Facebook and Microsoft each contributed $10,000 as gold sponsors. The donations put the tech companies in the top tier of the event’s backers. But the donations also put the firms in company with some of the event’s other sponsors, which included three groups known for their work attacking climate change science and trying to undermine efforts to reduce carbon emissions.

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Among the most notable was the CO 2 Coalition, a group founded in 2015 to spread the “good news” about a greenhouse gas whose increase in the atmosphere is linked to potentially catastrophic climate change. The coalition is funded by conservative foundations that have backed other climate change denial efforts. These include the Mercer Family Foundation, which in recent years has donated hundreds of thousands of dollars to right-wing think tanks engaged in climate change denialism, and the Charles Koch Institute, the charitable arm of one of the brothers behind Koch Industries, the oil and gas behemoth.

In the LibertyCon exhibit hall, the CO 2 Coalition handed out brochures that said its goal is to “explain how our lives and our planet Earth will be improved by additional atmospheric carbon dioxide.” One brochure claimed that “more carbon dioxide will help everyone, including future generations of our families” and that the “recent increase in CO 2 levels has had a measurable, positive effect on plant life,” apparently because the greenhouse gas will make plants grow faster.

In a Saturday presentation, Caleb Rossiter, a retired statistics professor and a member of the coalition, gave a presentation titled “Let’s Talk About Not Talking: Should There Be ‘No Debate’ that Industrial Carbon Dioxide is Causing Climate Catastrophe?” In his presentation, Rossiter told the assembled students that the impact of climate change on weather patterns has been vastly exaggerated. “There has been no increase in storms, in intensity or frequency,” he said. “The data don’t show a worrisome trend.”

He insisted that when he hears the news that carbon dioxide levels in the atmosphere are rising, “I’m cheering!” That’s because, he said, carbon dioxide “is a fertilizer” that has made Africa greener and increased food production there, reducing human misery.

Rossiter also claimed that carbon dioxide emissions correlate with wealth and that the greenhouse gas “improves life expectancy” because poor countries that start burning fossil fuels have a more consistent power supply and can then clean up their water. “I’m happy when carbon dioxide is up, because it means poverty is down,” he declared.

“I come not to bury your carbon but to praise it,” he concluded.

Rossiter’s presentation puts him on the far fringes of the climate denial world. Not even Exxon is trying to make such arguments anymore. And it’s a long way from what Google, Facebook, and Microsoft have said about the dangers of carbon dioxide; all three companies have committed to reducing their own carbon footprints. Microsoft has pledged to cut carbon emissions by 75 percent by 2030. Google claims to be committed to a “zero carbon” future and is aggressively pursuing renewable energy sources for its operations to reduce its carbon footprint and help combat climate change. And Facebook founder Mark Zuckerberg criticized President Donald Trump after he announced that the United States would withdraw from the Paris climate accord, writing, “Stopping climate change is something we can only do as a global community, and we have to act together before it’s too late.”