Rex Tillerson claims to believe in climate change and want a price on carbon. But his record as Exxon CEO says different.

As CEO of ExxonMobil, Rex Tillerson presided over the world’s largest publicly traded oil and gas company — a company that has come to represent, for climate activists, the very antithesis of climate action.

As Secretary of State, Tillerson will be the United States’ top diplomat, serving as an extension of U.S. policy worldwide. Past secretaries — especially John Kerry — have used the position to take an increasingly strong stance on climate action. It’s far from assured that Tillerson would do the same.

Unlike a handful of other top cabinet nominees — from EPA administrator to Secretary of the Interior — Tillerson does not appear to be a climate denier, telling an audience at the Oil & Money conference in October that “we [Exxon] share the view that the risks of climate change are real and require serious action.”

Exxon, as a company, has supported the Paris climate agreement —from which President-elect Donald Trump has promised to withdraw — and advocates for a revenue-neutral carbon tax. In June of this year, the company officially began ramping up its congressional lobbying efforts regarding a carbon tax, though that was before Trump won the Electoral College and Republicans retained control of Congress.

Now that Trump — a climate denier who has called climate change a “hoax” and falsely peddles the idea that the science on climate change isn’t settled — has won the Electoral College and the White House, it remains to be seen whether Exxon and Tillerson will recalibrate their position on things like the Paris agreement and a carbon tax.

Regardless of Exxon’s official stance, Tillerson certainly does not share the enthusiasm for climate action of his predecessor. Kerry has been active in environmental politics for decades, and has worked to underscore the connection between climate change and national security threats — a perspective he shares with the Pentagon. Tillerson, by contrast, has said that he does not feel climate change is the greatest challenge of his generation, arguing that its merely “an engineering problem” to which humans will adapt.

“We have spent our entire existence adapting, OK? So we will adapt to this,” Tillerson said at a Council on Foreign Relations talk in 2012. “It’s not a problem that we can’t solve.”

As CEO of Exxon — a company he has worked at for his entire adult life — Tillerson has a significant financial stake in the company. According to the company filings, Tillerson owns $218 million in Exxon stock, with another $70 million tied up in his pension plan. As Secretary of State, he would be required to divest of his shares, but it’s unclear whether he would be able to fully separate himself from the interests of the company.

And that presents a serious conflict, because as Steve Coll — who wrote the book Private Empire: ExxonMobil and American Power — points out, what is best for Exxon isn’t necessarily always what is best for the United States. One glaring example is Tillerson and Exxon’s relationship with Russia: In 2011, Tillerson personally helped negotiate a venture agreement that partnered Exxon with Rosneft, one of Russia’s largest state-owned oil companies, to explore oil production in the Arctic. It was a massive, $500 billion oil deal — one that Rachel Maddow summed up as being “expected to change the historical trajectory of Russia.”

Our next Secretary of State, left, with Russian President (then Prime Minister) in 2012. CREDIT: AP Photo/RIA-Novosti, Alexei Nikolsky, Government Press Service

Things didn’t quite work out that way, however. In 2014, the United States hit Russia with multiple rounds of sanctions in response to what it viewed as Russian aggression in eastern Europe, specifically in regard to Ukraine. Part of those sanctions prohibited the transfer of advanced offshore or shale oil technology to Russia. That same year, Exxon discovered a major oil field with about 750 million barrels of new oil as part of the previous exploratory deal with Rosneft — and if sanctions were lifted, Exxon would have rights to extract oil from that field. If all those barrels were to be extracted and burned, it would be the equivalent of 81.5 new coal-fired power plants being built in one year.

So lifting those sanctions would be bad for the climate but great for Exxon, which could have lost around $1 billion due to the sanctions.

Russia, for its part, has yet to officially join the Paris climate agreement — and if the United States, the world’s largest historic emitter, pulls out of the agreement, Russia could easily refuse to join the agreement in perpetuity.

Tillerson will have more than just Russian sanctions on his plate as Secretary of State. He’s likely to face a renewed push from TransCanada, which has indicated that it intends to restart its efforts to build the Keystone XL pipeline. The fight over the controversial pipeline — which would stretch from Canada’s tar sands through the midwestern U.S. — raged for almost all of President Obama’s tenure; in 2013, Tillerson urged the Obama administration to approve the pipeline, arguing that they were putting “politics before our already rigorous regulatory permitting process.” In November of 2015, the State Department finally rejected TransCanada’s permit — which was required for the pipeline to cross the U.S.-Canada border. Secretary of State John Kerry said that building the pipeline “would significantly undermine our ability to continue leading the world in combating climate change.”

As Exxon CEO, Tillerson had reason to be supportive of the pipeline. According to a September report from InsideClimate News, tar sands account for 35 percent of the company’s liquid holdings — a figure that has grown substantially in the past decade. But tar sands are an especially carbon-intensive fuel, giving off far more carbon emissions than traditional oil extraction.

Following Trump’s announcement that he would be nominating Tillerson, Robert Stavins, director of the environmental economics program at Harvard University, took to Twitter to voice cautious optimism that the pick might be a voice of reason in a cabinet that otherwise seems poised to outright reject the mainstream consensus on climate change.

But climate and environmental groups were quick to oppose the pick, citing a slew of concerns — from Tillerson’s close ties to Russia to his potential role in Exxon’s decades of climate deception and misinformation.

“Appointing Rex Tillerson to be our chief diplomat is an affront to global progress and will place the U.S. economy, our security, and our standing in the world in the same failing predicament Exxon is in right now,” Greenpeace executive director Annie Leonard said in a statement. “The global community continues to send a strong, collective message that it is ditching fossil fuels for clean energy. Rex Tillerson hid climate science so it could cash in on disaster, instead of transitioning his company to a position of true leadership. This appointment is a desperate grab for power by a failing industry that is perfectly fine bringing the American people down with it.”

Of all of Trump’s recent nominees, Tillerson likely faces the most uphill battle with regards to confirmation —Sen. Marco Rubio (R-FL), for instance, has already raised concerns about Tillerson’s nomination. But should he be confirmed as the next Secretary of State, it’s unclear which version of Tillerson the world will get: the businessman interested in a market-based approach to climate action, or the Exxon CEO whose vast wealth is tied to the continued extraction of fossil fuels, whatever the cost.