In 1978, a young chemical engineer named Edward Garvey was hired by Exxon to develop a research project aboard a supertanker called the Esso Atlantic. Outfitted with an array of sampling instruments, the ship crisscrossed the Atlantic from the Gulf of Mexico to the Persian Gulf, measuring carbon-dioxide concentrations in the air and in the ocean. The goal, according to Garvey, was “to make an important contribution to the understanding of CO2 climate science.”

Garvey described the supertanker project on Wednesday during a forum convened by members of the Congressional Progressive Caucus and the Sustainable Energy and Environment Coalition, titled “Oil Is the New Tobacco.” The forum examined the contradictions between Exxon’s internal approach to global warming, which the company began to take seriously as early as the late 1970s, when it invested in projects like the Esso Atlantic; and its public campaign to cast doubt on climate science, which began about decade later. In recent months Exxon has tried to distract from its checkered history, insisting that inquiries are an affront to free speech. Wednesday’s event indicated that at least some Democrats are not so easily put off.

“Just like R.J. Reynolds and Philip Morris before them, Exxon Mobile said one thing in public, and something else in private,” testified Naomi Oreskes, a professor at Harvard and co-author of a history of climate skepticism called Merchants of Doubt. Oreskes traced the history of climate-change denial back to the late 1980s, to a Washington, DC–based think tank, the George C Marshall Institute, founded by a former tobacco-industry consultant. The institute applied the “tobacco strategy” to block action on climate, producing reports that challenged the scientific consensus around global warming. Exxon became a major funder of the institute and other denial groups in the 1990s, and played a “leading” role in the Global Climate Coalition, an industry group created “with a specific goal of preventing the US Congress from signing the Kyoto protocol,” Oreskes recounted. While Exxon claims it’s stopped funding such groups, Oreskes pointed out that it’s still a member of three trade associations that advocate against climate action: the American Legislative Exchange Council, the Chamber of Commerce, and the American Petroleum Institute.

The forum adds to the pressure Exxon is already under from the state attorneys general who’ve opened investigations into whether the company deliberately misled investors about the risks of climate change. Prosecutors in New York and Massachusetts have issued subpoenas requesting numerous financial records and other documents, modeling their efforts on the litigation against tobacco companies, which was also led by state attorneys general and resulted in a $200 billion settlement. Meanwhile, the Department of Justice, which won its own racketeering suit against the tobacco companies, has asked the Federal Bureau of Investigation to look into Exxon’s behavior. Congressional hearings were a key part of efforts to hold Big Tobacco accountable, too; but with Republicans in control of both chambers of Congress, Wednesday’s forum may be as close to an official hearing as is possible.

“The fossil-fuel industry’s concerted effort to confuse the public on the certainty of climate science is endangering nearly everyone on this planet, born and yet to be born, all for one simple reason: money,” Representative Keith Ellison, who co-chairs the Progressive Caucus, said at the beginning of the forum. While the room was packed with onlookers, many of the seats reserved for representatives were empty because of the sit-in occurring simultaneously on the floor of the House of Representatives. “Climate action is not the only thing to be obstructed around here,” Ellison said, referring to gun control. Where climate is concerned, the “opportunity cost” of that obstruction is enormous. Oreskes pointed out that while there was already interest in renewables in the late 1970s—Jimmy Carter put solar panels on the White House, only to have Reagan remove them—the fossil-fuel industry’s campaign against climate science helped to delay the development and scaling-up of clean technology for decades.

In addition to Garvey and Oreskes, the forum included Kathy Mulvey of the Union of Concerned Scientists, who described her research revealing that Exxon was aware of the dangers of climate change as early as 1981 and yet, along with other fossil-fuel companies, actively sought to deceive the public; and Natasha Lamb of Arjun Capital, who argued that climate change is “the biggest business risk Exxon faces this century,” citing a recent Citibank analysis that concluded that meeting the goals set at the Paris climate conference would require $100 trillion of fossil-fuel assets to be left in the ground. While Exxon proceeds with business as usual, its debt level has more than doubled. In April, for the first time since the Great Depression, Exxon’s credit rating was downgraded. “It’s clear growing high-cost fossil-fuel reserves is no longer a proven path forward for Exxon and its investors,” Lamb said. “We believe Exxon must shift from a growth plan to one focused on value, and right size its business for a two-degree demand level—essentially, shrink profitably.”

In response to the congressional and legal scrutiny, Exxon and its allies have tried to change the topic, claiming that the company’s right to free speech is under attack. (In fact, the AGs are investigating Exxon not for its political speech but for lying to investors—those are very different things, from a legal standpoint.) They’ve also tried to concoct a controversy about “collusion” between the prosecutors and environmental groups. Late last week, the Republican who chairs the House Science Committee, Lamar Smith, reissued a demand to the state attorneys general, along with several nonprofit groups including the Union of Concerned Scientists, that they turn over documents and communications related to their investigations of the oil company. Smith claims the state investigations may “infringe on the civil rights of scientists”—a remarkably rich statement coming from Smith, who spent nearly a year harassing scientists at NOAA whose research conclusions were inconvenient for him. In fact, Smith himself has issued more subpoenas in his three-plus years as science committee chairman than the committee had in its entire 54-year history previously. So far the AGs have declined to comply with Smith. Given his penchant for subpoenas, it seems likely things will only get more contentious from here.