As chairman and CEO of ExxonMobil, Rex Tillerson admitted that climate change is real. In January 2009, he said the company was in favor of a carbon tax. A few years later, Exxon endorsed the Paris Agreement.

It was never clear whether Exxon’s leaders actually supported those policies or whether they were trying to put their best PR foot forward (or whether it mattered either way). But now Tillerson is the Secretary of State-designate for a man who not only rejects the Paris treaty, but who also once tweeted that climate change is a hoax invented by the Chinese. What does Tillerson really think about global warming—and will it matter?

On Wednesday, at his ongoing confirmation hearings in front of the Senate Foreign Relations Committee, we’ve gotten four big glances at his views on the issue:

1. Senator Tom Udall, a Democrat of New Mexico, pressed Tillerson to share his “personal view” of climate change. Tillerson replied that after 20 years as a scientist and engineer, he had concluded that “the risk of climate change does exist.” He also believed “action should be taken,” though he neither went into detail nor left the passive voice.

“Do you believe that human activity, based on science, is contributing?” asked Bob Corker, a Tennessee Republican who chairs the Senate Foreign Relations Committee.

“The increase in greenhouse gas in the atmosphere is having an effect. Our ability to predict that effect is very limited,” Tillerson answered.

A few notes here. First, as Inside Climate News points out, Tillerson never connected emissions from fossil fuels to the rise in greenhouse-gas levels. But oil, gas, and coal combustion contribute not only most of the ongoing global warming but also all of the ongoing ocean acidification. Second, Tillerson is careful to frame climate change as a future risk and not an ongoing reality. Yet the last three years have been the warmest ever recorded, and the U.S. East Coast is already seeing elevated sea levels, especially in South Florida. Most scientists also feel quite certain about many of the ill effects of climate change.

Still, it pointed to a potential shift in the Republican Party’s treatment of climate change. If some party members stop debating whether global warming is real (it is), and begin discussing what to do about it, the odd politics of the issue in the United States could begin to change.

2. Tillerson made comments about international climate treaties that—in any reasonable reading—do not agree with those of Donald Trump.

“I think it’s important that the United States maintain its seat at the table in the conversation on how to address threats of climate change. They do require a global response. No one country is going to solve this alone,” he said.

Immediately after Trump’s victory, there were hints that he may direct the United States to leave the UN Framework Convention on Climate Change, the overarching (and Congressionally ratified) treaty to address global warming. It’s hard to reconcile the U.S. “maintaining its seat at the table” with its abandoning the UNFCCC, as that would leave the U.S. unable to attend the UN’s annual meeting on climate change. It’s less clear what his comment means for the Paris Agreement.

Since presidents ultimately set all policy, it’s also unclear whether Tillerson’s opinions about climate diplomacy may matter. But as the leader of an American business, it makes sense that he would see American engagement in global affairs as worthwhile.

3. Tillerson clarified his support for a carbon tax. When he announced Exxon’s endorsement of a carbon tax on January 9, 2009, it was because he opposed the incoming Obama administration’s plans for a cap-and-trade plan, he told the committee.

Back then, he called a carbon tax “a more direct, a more transparent, and a more effective approach.” He largely echoed that reasoning on Wednesday.

“It replaces the hodgepodge of approaches we have today, which are scattered. Some of which are through mandates, some of which are well-intended, but ineffective incentives,” Tillerson told Udall.

He also liked that a carbon tax would not increase the size of the government. “If a carbon tax is put in place, it has to be revenue-neutral. All the revenues have to go back out to the economy through reduced employee payroll taxes,” he said. “This is simply a mechanism to incentivize choices that people are making. It’s not a revenue-raiser.”

Tillerson did not commit to working for a carbon tax while secretary of state.

4. Tillerson got the senators to laugh about the notion of harassing the civil service.

In early December, the Trump transition team circulated a survey among employees at the Department of Energy. It sought to learn, among other things, about which employees had worked on or studied climate issues and about who had attended international climate meetings with Obama political appointees.

In response to ferocious opposition, the transition team withdrew the survey later that week.

At the hearing, Udall asked Tillerson whether he would seek out or persecute State Department employees who had worked on climate issues for the Obama administration.

“No sir, that’d be a pretty unhelpful way to get started,” replied Rex. The committee chuckled.

Amid all of this, the loudest voice in the room about climate change wasn’t from a senator or the nominee. Throughout the morning, protesters stood up in the gallery and shouted their opposition to the proceedings.

“Exxon wants to drill and burn the Arctic,” yelled a woman with graying hair. “Please don’t put Exxon in charge of the State Department. Protect our children and grandchildren!” she shouted.

A Capitol Police officer escorted her out. Corker said he would “stop the clock” and allow senators their full questioning time whenever the proceedings were interrupted. The hearing continued.