Climate change will be front and center at the two days of hearings on the confirmation of President-elect Trump's pick to lead the State Department, former Exxon Mobil CEO Rex Tillerson.

But as one top Democrat put it after a recent meeting with Tillerson, climate change is but one concern, given that it is not clear what Trump's foreign policy positions are outside of bashing efforts to combat global warming.

"I was pleased to learn more about [Tillerson's] position on climate change policy," Sen. Tom Udall, D-N.M., said Thursday after meeting with the former oil executive. "I'm encouraged that, contrary to the extreme statements by President-elect Trump, Mr. Tillerson believes in science and sees value in the United States remaining a party to the Paris Agreement."

Udall said he also appreciated that Tillerson has "advocated for solutions" to reduce carbon pollution, "rather than denying the existence of climate change." But he noted that Tillerson couldn't help the senator understand where Trump stood on a number of other top foreign policy issues.

Although he said he was "impressed by Mr. Tillerson's direct answers to my questions, he was unable to clarify what President-elect Trump's policies and positions will be," Udall said, suggesting that the hearing will be as much about Trump as it will be about Tillerson.

"He will have his work cut out for him as top diplomat if the president of the United States continues his dangerous habit of voicing volatile foreign policy and national security opinions by tweet," said Udall.

Political observers say Russia likely will dominate the two days of hearings, scheduled for Wednesday and Thursday. But other points about Trump's foreign policy agenda are coming up, such as where he stands on the issue of foreign aid and assistance or whether he plans to scrap such programs.

Beth Schwanke of the Center for Global Development said in a blog that she isn't hopeful for such nuts-and-bolts issues of foreign policy to come up.

"No one expects to hear much on development-related matters during next week's hearing for Secretary of State nominee Rex Tillerson," she wrote. "While Russia will almost certainly dominate, I expect members of the Senate Foreign Relations Committee to raise questions on climate change and perhaps a few on ongoing humanitarian crises.

"But even if they aren't asked outright, I'll be listening closely to Mr. Tillerson's testimony for answers to some fundamental questions about what we can expect from the next four years for U.S. development policy," she added.

Udall might be the one to raise the foreign aid issues, since he is the top Democrat on the Foreign Relations Committee's panel on international development.

Udall served as his state's attorney general and senior counsel for New Mexico's environmental department, so he is steeped in the law and likely to be pointed in his questioning.

That was apparent when Udall met with Tillerson. He voiced the strongest skepticism over Tillerson about his foreign ties.

"Like many New Mexicans, I am concerned and skeptical about a career executive of a massive oil and gas company — who has no government experience — serving as the nation's secretary of state," Udall said.

A lot of that skepticism comes from Exxon's overseas oil and gas interests that are vast and spread across the world, including areas of major significance such as Russia, Iraq and Latin America, the senator said.

"While I compliment Mr. Tillerson on officially divesting from Exxon, this is an unprecedented nomination for many reasons," Udall said. "I think the American people deserve more assurance than we've received so far that he will be able to represent their values when U.S. policy goals conflict with Exxon's ongoing corporate interests."

Udall wants Tillerson to disclose his tax information to the public, as a matter of securing trust with the American people. That will be something to look out for beginning Monday.

Tillerson told Udall in their meeting that "he is willing to make his tax information public, and I strongly urge him to release his tax returns before the U.S. Senate Foreign Relations Committee confirmation hearings begin on Wednesday." It was not clear if Tillerson would be willing to concede to the Democrat's suggestion before the hearings.

Release of tax information has been a sticking point that Democrats have raised with Trump himself. On Friday, Udall signed onto a bill introduced by a number of top Democrats that would require Trump discloses his financial information, while strengthening the requirement when it comes to other presidential nominees in the future. The bill was authored by Sen. Ron Wyden, D-Ore., the top Democrat on the Finance Committee.