New efforts by President Trump and his staff to question or undermine the established science of climate change have created a widening rift between the White House on one side, and scientific facts, government agencies, and some leading figures in the president’s own party on the other.

The president’s senior advisers are exploring the idea of creating a panel aimed at questioning the National Climate Assessment. According to a White House memo, the group would include William Happer, a Princeton physicist who has asserted that carbon dioxide — a greenhouse gas that scientists say is trapping heat and warming the planet — is beneficial to humanity.

The climate assessment, a sweeping report issued by the White House itself in November, concluded decisively that the burning of fossil fuels was warming the atmosphere, leading to a raft of harmful effects across the United States and the world.

And Mr. Trump announced last week on Twitter that he would nominate Kelly Knight Craft to be his ambassador to the United Nations. Ms. Craft said in a 2017 television interview that, on the issue of climate change, she believes there are “scientists on both sides that are accurate.”

“There is no precedent for something like this,” said Douglas Brinkley, a historian who has written books on five former United States presidents. “Other presidents have attacked policy initiatives, but not science.”

At the same time, more senior Republicans, including those in Congress, are moving in the opposite direction, acknowledging the established science and publicly calling to reduce fossil fuel pollution.

To be sure, some Republicans continue to question, or, more commonly, to remain silent on the issue of human-caused climate change.

But in February, three of the top-ranking Republicans on the House Energy and Commerce Committee, Greg Walden of Oregon, Fred Upton of Michigan, and John Shimkus of Illinois, published an op-ed on the website Real Clear Policy in which they said, “climate change is real” and called for innovations to “reduce greenhouse gas emissions.”

Similarly, in December, Senator John Barrasso, the Wyoming Republican who is chairman of the Senate Environment Committee, wrote an op-ed in The New York Times in which he acknowledged his acceptance of climate science but also criticized the Paris Agreement and proposals to tax carbon dioxide emissions.

Republican pollsters and staff members said the White House’s efforts to attack the science — that fossil fuel pollution traps heat, warms the planet, and contributes to more severe droughts, heat waves and hurricanes — could backfire and put Mr. Trump fundamentally at odds with his own party.

“A lot of thoughtful Republicans have accepted the reality of climate change and are wrestling with questions of policy,” Whit Ayres, a prominent Republican pollster, said.

Mr. Ayres noted that many Republicans had concerns about climate change policies like taxing or regulating coal and oil pollution. But he said that questioning the foundational science of climate change could become a political liability.

“There are perfectly legitimate questions to be raised about whether a dollar spent fighting climate change is better spent on health care or education,” Mr. Ayres said. “But there are no longer credible questions to be raised about the existence of climate change. If the White House ends up there, that is simply not credible.”

White House officials initially sought to play down the National Climate Assessment by publishing it late in the afternoon the Friday after Thanksgiving. But its dramatic findings — that the impacts of climate change could knock as much as 10 percent off the size of the American economy by century’s end — received a lot of attention around the country.

Analysts also noted that the findings of the assessment could provide legal ammunition to opponents of Mr. Trump’s efforts to roll back climate change regulations, since the report makes the case that increasing greenhouse emissions is harmful to humanity.

It was those factors that prompted the White House effort to establish a panel or committee that would question or contradict those comprehensive scientific findings, according an administration official, who was not authorized to discuss the matter publicly and who spoke on condition of anonymity, and a former senior White House official with knowledge of the matter.

But the creation of such a panel, should it come about, would put Mr. Trump in a highly unusual position.

In particular, experts said, presidents have never sought to undermine the findings of the National Academies of Science, created by President Abraham Lincoln to provide unbiased scientific findings to the country’s leaders. The group played a key role in reviewing the conclusions of the National Climate Assessment.

“If there is one body that has the thorough respect of scientists and policymakers, it is the National Academies,” said Michael Oppenheimer, a professor of geosciences and international relations at Princeton University. “I can’t recall any time that an administration has tried to debunk a review by the National Academy, or where the White House ever tried to ‘re-review’ something the academy has reviewed.”

Critics of the president also singled out his announcement that he would nominate Ms. Craft as ambassador to the United Nations, given that her comments on climate change are far outside the mainstream of established science.

“She’s taken this bizarre position,” said R. Nicholas Burns, who served as under secretary of state for political affairs during the George W. Bush administration. “She will find that in New York, at the Security Council, climate change is one of the top issues. If the representative of the world’s largest economy and one of the largest emitters doesn’t understand the science of this issue, it makes the U.S. look feckless and irresponsible.”

Ms. Craft, currently the United States ambassador to Canada, and her husband, Joseph W. Craft III, a billionaire coal magnate from Kentucky, were major contributors to Mr. Trump’s 2016 presidential campaign and donated to his inaugural committee.

A White House spokeswoman declined to speak on the record for this article.

The moves by the White House come as public opinion in the United States and around the world appears to be falling more in line with the science.

Globally, climate change is seen as the top international threat, according to a poll conducted in 26 countries and published this month by the Pew Research Center.

The Trump administration has been criticized by other countries for Mr. Trump’s plans to withdraw the United States from the Paris climate agreement and for his policy moves to weaken Environmental Protection Agency rules.

But the new plans to create the panel and the expected nomination of Ms. Craft will sharply deepen that divide, said Sherri Goodman, who served as a deputy under secretary of defense in the Clinton administration.

“It creates a huge divide with our European and Asian allies, and it allows China to claim the mantle of climate leadership,” she said. “China shows up at climate conferences when the U.S. doesn’t, and they offer to engage on the science.”

In the United States, polling consistently shows that more than half of Americans now accept that climate change is caused by human activities. While most surveys show that among Republicans, less than half accept that science, the data also reveals a sharp generational divide among Republicans.

A 2018 poll by the Pew Research Center found that just 18 percent Republicans born in the postwar baby boom accepted the reality of human-caused climate change, but twice that number of millennial Republicans, defined as those born from 1981 through 1996, accepted that science.

In addition, the poll found that 45 percent of millennial Republicans said they were seeing at least some effects of global climate change in the communities where they live, compared with a third of baby boomer Republicans.

That fact is not lost on political analysts.

“For Republicans who believe pollsters, pollsters are telling them, ‘people care about climate,’ ” said Steven J. Milloy, a member of Mr. Trump’s E.P.A. transition team who now runs a website aimed at casting doubt on the established science of human-caused climate change.

Mr. Milloy and other Republican strategists also said that within the White House, millennial Republican staffers were pushing back at the effort to create the new panel.

“If you’re 30 years old and work at the White House, it’s not clear that this effort is a good idea,” said Mr. Milloy.

But he added that for Mr. Trump’s base of supporters, none of that matters. “People like me, we love the guy.”