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 couldnt speak for a company he no longer works for.

Since Im no longer with Exxon Mobil, I cant 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 Mobils alleged cover-up, Tillerson said, a little of both.

Sen. Tim Kaine (D-Va.) was not impressed by Tillersons dodge.

I felt like what he was really saying was Im 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 couldnt refute it, Kaine said. I gave him the opportunity is it true, or is it false tell me its 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 didnt help his cause.

He was not required [to answer]. Hes 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, thats 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.