A little less than seven years ago, the climate scientist Michael Mann ambled into his office at Penn State University with a wedge of mail tucked under his arm. As he tore into one of the envelopes, which was hand-addressed to him, white powder tumbled from the folds of the letter. Mann recoiled from the grainy plume and rushed to the bathroom to scrub his hands.

Fortunately for Mann, the FBI confirmed the powder was cornstarch rather than anthrax. It was perhaps the nadir of the vituperation hurled at Mann by often anonymous critics who accuse him and others of fabricating or exaggerating the dangers of climate change.

“Michael has most certainly become a lightning rod,” said Kerry Emanuel, an MIT climate scientist, although this doesn’t mean others have been shielded.

Emanuel himself has previously received emails threatening him and his family. The Texas Tech University professor Katharine Hayhoe, who has gathered a healthy following for her Facebook posts that mix climate science with evangelism, has opened her inbox to missives including “Nazi Bitch Whore Climatebecile” and a request that she “stop using Jesus to justify your wacko ideas about global warming”.

Threats and badgering of climate scientists peaked after the theft and release of the “Climategate” emails – a 2009 scandal that was painfully thin on scandal. But the organized effort to pry open cracks in the overwhelming edifice of proof that humans are slowly baking the planet never went away. Scientists are now concerned that the election of Donald Trump has revitalized those who believe climate researchers are cosseted fraudsters.

Mann said climate scientists “fear an era of McCarthyist attacks on our work and our integrity”. The odd unfulfilled threat may be perturbing but a more morale-sapping fear is that the White House and Congress will dig up and parade seemingly unflattering emails, sideline or scrap research and attempt to hush the scientific community.

“I faced all of those things a decade ago, the last time Republicans had full control of our government,” said Mann, who has been pursued on and off since 2010 when Virginia’s then attorney general, Ken Cuccinelli, unsuccessfully demanded that the University of Virginia hand over all of Mann’s correspondence to see if he had obtained grants fraudulently. The American Tradition Institute, a free-market thinktank, followed up with a records request for the same correspondence.