During the first Trump administration, Virginia Burkett, a senior government scientist, felt like she had a target on her back.

She fought attempts by Trump officials to eliminate climate research programs while also rejecting their requests that she alter the nation’s premiere report on how global warming affects every region of the country.

But Dr. Burkett says she paid a price. In a whistle-blower complaint, she said the Trump administration retaliated by demoting her and removing her as chair of the committee overseeing the report.

Her experience was part of a broad assault on science across the federal government during the first Trump administration. Other scientists were also demoted or reassigned, projects were disrupted and scientists were pressured to delete their research or were blocked from publicizing it. In the end, hundreds of scientists and experts in environmental policy left the government.

But Dr. Burkett was reinstated to a senior position by the Biden administration and has remained in federal service, along with thousands of others. And with Mr. Trump about to return to the White House, they have pushed for new policies and procedures to guard against political interference.

“I’m most concerned about protecting future scientists from the harms that I faced,” she said, echoing the views of about two dozen current and former government scientists and policy officials interviewed for this article.