U.S. climate scientists say they worry the incoming Trump administration might do video of teens having anal sexmore than cut off their research funding. Some also fear they could receive personal attacks and death threats simply for doing their jobs.

Michael Mann, a climate researcher at Penn State University, said he knows exactly what that's like.

Over the last decade, Mann has been singled out by Republican senators and Pennsylvania and Virginia officials, who falsely accused the scientist of distorting his data and perpetuating the "hoax" that human activities are causing climate change.

"I've faced hostile investigations by politicians, demands for me to be fired from my job, threats against my life and even threats against my family," Mann said in a Sunday op-ed in the Washington Post.

Mann, who directs Penn State's Earth System Science Center, recalled the time in 2010 when he opened an envelope at his desk and white powder fell into his fingers, which at first he feared was anthrax. (It was cornstarch.) He used to get emails with warnings like "the public will come after you" or suggesting he'd find himself "six feet under."

Mann said those threats have diminished in recent years as more Americans have come to understand and accept the global scientific consensus on human-caused climate change -- and as President Barack Obama accelerated efforts to fight greenhouse gas emissions and develop renewable energy.

But President-elect Donald Trump has vowed to undo many of Obama's gains on climate change.

Trump himself is a climate-denier who recently claimed, falsely, that "nobody really knows" what's happening to the planet. Many of his cabinet picks, including for Environmental Protection Agency administrator and Secretary of Energy, similarly reject the scientific conclusions shared by 97 percent of the world's climate scientists.

The Intergovernmental Panel on Climate Change, the world's most authoritative group of climate experts, has said it is "extremely likely" that human-caused greenhouse gas emissions have been the "dominant cause" of observed global warming trends since the mid-20th century.

Mann said that he and his colleagues are now "bracing for a renewed onslaught of intimidation, from inside and outside government," given the coming changes in Washington.

"I fear the chill that could descend," he wrote in the op-ed.

Those fears aren't only based on past events.

The Trump transition team in early December sent an unusually detailed questionnaire to the Energy Department, which demanded the names of employees who attended U.N. climate talks in the last five years or assisted in other climate-related projects under Obama.

Trump's team later backed away from the questionnaire after the Energy Department issued a statement saying that the memo "left many in our workforce unsettled" and that the agency would not turn over the names of individuals.

At a rally last week in San Francisco, hundreds of climate scientists, including Mann, promised to "stand up for science" during the Trump administration.

"We're people with real fears, both as scientists and as citizens," Geoffrey Supran, a rally organizer and MIT and Harvard climate researcher, told Mashable.

"I see that as more reason for us to stand up for what we know to be true," he said.