Rex Tillerson, President-elect Donald Trump’s pick for secretary of state, refused to answer questions on Wednesday about how much Exxon Mobil Corp. knew about climate change.

Tillerson, who worked at the oil giant for 41 years and served as its chief executive for a decade, said he couldn’t speak for a company he no longer works for.

“Since I’m no longer with Exxon Mobil, I can’t speak on their behalf,” Tillerson said. “The question would have to be put to Exxon Mobil.”

For years, Exxon Mobil funded a Big Tobacco-style disinformation campaign aimed at undermining public understanding of the science behind global warming. Documents published in 2015 by InsideClimate News and the Los Angeles Times revealed that the company understood climate change decades ago and deliberately covered up the evidence to protect its financial interests. The reports spurred a coalition of state attorneys general to begin investigating corporations that mislead the public about climate change, including Exxon Mobil.

Tillerson pledged in 2007 ― one year after he took the top job ― to halt donations to some of the most radical groups producing misleading research on climate change. But the company continued to spend millions on groups that seed doubt over whether burning fossil fuels worsen climate change.

Asked whether he lacked the knowledge or was refusing to answer questions about Exxon Mobil’s alleged cover-up, Tillerson said, “a little of both.”

Sen. Tim Kaine (D-Va.) was not impressed by Tillerson’s dodge.

“I felt like what he was really saying was ‘I’m refusing to answer the question.’ He has the knowledge,” Kaine told The Huffington Post. “By saying ‘a little bit of both,’ even that was cagey. He was refusing to answer the question. He knew that, and he knew I knew that.”

Tillerson demurred “probably because he couldn’t refute it,” Kaine said. “I gave him the opportunity — is it true, or is it false — tell me it’s false.”

Kaine, who has a reputation as a centrist and is facing re-election in a swing state in 2018, might have been regarded as one of 10 or 11 Democrats who at least have a political rationale to entertain Trump nominees. But Kaine suggested Tillerson didn’t help his cause.

“He was not required [to answer]. He’s not subpoenaed, nor is he under oath,” Kaine said. “But he is trying to earn my vote, and refusing to answer a question that I think is highly relevant to the job, that’s not a great way to win a vote.”

Under ethics laws, Tillerson must recuse himself from State Department decisions involving Exxon Mobil for one year. After that, Tillerson said he would consult the ethics counsel any time he dealt with his former employer, but declined to commit to a blanket recusal during his four-year term.

He hinted that he supports maintaining the Paris climate agreement that 180 countries, including the U.S. and China, have signed.

“It’s important that the United States maintain its seat at the table with the conversations around how to deal with the threats of climate change,” he said.

Later in the hearing, he said he plans to conduct a “fulsome review” of climate policies, but hinted that he would not support long-term deals that disadvantage the U.S. economically.

“The president-elect, as part of his priority in campaigning, was ‘America First.’ So there are important considerations as to when we commit to such accords,” he said. “It’s important for America to remain engaged in those discussions so we are at the table, expressing a view and understanding what the impacts may be on the American people and American competitiveness.”

Jonathan Ernst / Reuters Protesters interrupted the proceedings at least four times by holding up signs with the words “Reject Rexx” written in the same font as Exxon Mobil’s logo and shouting “oil is dead” and “please don’t put Exxon in charge of the State Department.”

Still, he said he believes global warming is occurring.

“The increase in greenhouse gases in the atmosphere is having an effect,” he said, but he refrained from linking burning fossil fuels to the rise. He also said he remained skeptical over scientists’ ability to predict the change.

“The risk of climate change does exist and the consequences could be serious enough that action should be taken,” he added. “The type of action seems to be where the largest areas of debate exist in public discourse.”

Sen. Tom Udall (D-N.M.) asked whether Tillerson agrees with Exxon Mobil’s corporate stance on climate change, which states that the risk is clear and merits action.

“I do not take exception to that statement,” Tillerson said. “I might articulate it a little differently as to my personal views.”

He said Trump, who has repeatedly called climate change “a hoax” and “a bunch of bunk,” has invited his views on the subject.

“He has asked for them,” Tillerson said. “He knows that I am on the public record with my views. And I look forward to providing those, if confirmed, to him, in discussions around how the U.S. should conduct its policies in this area.”

“Ultimately, the president-elect was elected, and I’ll carry out his policies in order to be as successful as possible,” he added.

Tillerson reiterated his support for a tax on carbon, a policy he publicly backed in 2009 in response to a congressional push to establish a cap-and-trade system. Exxon Mobil lobbied heavily against the bill, and some environmental leaders accused the company of backing a carbon tax, something considered less politically feasible, to undermine cap-and-trade.

But Tillerson said a tax on carbon would reduce greenhouse gas emissions, but insisted the policy must be revenue neutral to mitigate jobs lost in the fossil fuel sector.

“Let’s simplify the system,” he said. “This is the one and only effort we’re going to take to begin to try to influence people’s choices.”

Even so, he said he would not advocate for such a tax as secretary of state.

“When it gets to tax policy, that’s going to be the responsibility of other agencies to conduct,” he said. “My role at State would be only to deal with those issues that are relevant to treaties or international accords that we’ve entered into in terms of our compliance in those and participation in those.”

Toward the end of the nine-hour hearings, Tillerson downplayed whether global warming contributes to national security risks.

“I don’t see it as the imminent national security threat that perhaps others do,” Trump’s pick for secretary of state said.

Tillerson acknowledged that a severe drought, which drove Syrian farmers to abandon their fields and flock to cities, helped spark the bloody civil war in that country. But he dismissed studies that blame climate change for worsening the drought.

“Facts on the ground are indisputable in terms of what are happening with drought, disease, insect population,” Tillerson said. “The science behind the clear connection is not conclusive. There are many reports out there that we are unable yet to connect specific events to climate change alone.”

He then parroted a line frequently used by the sort of climate science deniers Exxon Mobil funds, placing equal value on both sides of the debate.

“There’s some literature out there that suggests that,” Tillerson said. “There’s other literature that says it’s inconclusive.”

This article has been updated with more details from the hearings. Michael McAuliff contributed reporting.