Microsoft, Google, and Facebook have all publicly promised to fight climate change, but now their commitment is seriously being called into question.

A damning report from Mother Jones reveals that all three of these tech giants were sponsors of a political student conference called LibertyCon, which repeatedly promoted climate change denialism at a recent event in Washington, DC.

Out of all three companies, Google donated the most, offering up US$25,000 for platinum sponsorship, while Facebook and Microsoft each contributed US$10,000 for a spot at the gold table.

These hefty sums were among some of the largest donations for the event, seating the tech giants alongside a number of organisations that are notorious for their attacks on climate science.

Entering the event's exhibit hall, attendees were reportedly given pamphlets detailing how Earth will actually be improved by more atmospheric carbon dioxide.  

One of the brochures apparently even claimed that "more carbon dioxide will help everyone, including future generations of our families" and that the "recent increase in CO2 levels has had a measurable, positive effect on plant life".

These were the inspiration of the CO2 Coalition, an organisation dedicated to pointing out "the important contribution made by carbon dioxide and fossil fuels to our lives and the economy". Unsurprisingly, the coalition is partly funded by none other than the Charles Koch Institute, a charity run by the brothers of the oil and gas giant, Koch Industries.

Under the CO2 Coalition's sponsorship, Caleb Rossiter, a retired statistics professor and infamous climate denier, was given a stage and a microphone. In his speech, he reportedly told the assembled students that when he hears that carbon dioxide levels are rising, he cheers because it "improves life expectancy".

Other activities at the conference were funded by The Heartland Institute, which has recently received a fair amount of media coverage for sending climate change-denying pamphlets to 200,000 teachers around the US.

The non-profit, which pushed President Trump to withdraw from the Paris climate accords, has reportedly received at least $676,500 from ExxonMobil since 1998, although it no longer discloses its funding sources.

The Heritage Foundation, another conservative group that supported the Paris agreement withdrawal, was yet another climate change-denying sponsor at the event.

At first, it's hard to fathom why these tech giants would want to keep such dubious company, especially at a conference that stands so firmly against their own, self-espoused policies.

Google is supposedly committed to a "zero carbon" future, promising to "meet the challenges posed by climate change"; Microsoft has pledged to cut carbon emissions by 75 percent by 2030; and Facebook founder Mark Zuckerberg has loudly criticised President Donald Trump for leaving the Paris climate accord.

Mother Jones reporter Stephanie Mencimer proposes a reasonable explanation for the hypocrisy. With more and more talk about government regulation of tech, she argues, these companies have prioritised another battle at the expense of fighting climate change.

At the conference, Google alone sponsored two different sessions, one called "Why Permissionless Innovation Needs To Be Defended" and another titled "Will the Government Continue to let the Internet be Awesome? Examining regulatory threats on many fronts".

All three tech giants have since defended themselves in a similar way to the criticisms stemming from the controversy. Essentially, they argue, just because we have funded one aspect of this conference, does not mean we condone the entire agenda or agree with its other sponsors or speakers.

Google even claimed that it was sponsoring the event to "promote strong technology laws", although the subjects of its sponsored sessions might have some questioning that.

Whatever their ultimate goal may have been, at the very least, this new and revealing report brings their true motivations into question.

"The companies' underwriting of a conference with a climate denier on the schedule shows the hazards of trying to advance a policy agenda through interest groups without also supporting their fringe elements," Mencimer writes for Mother Jones.

You can read her report in full here.