German climatologist Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research and a scientific advisor to Chancellor Angela Merkel, was reportedly threatened in Melbourne last year during a guest lecture, when a member of the audience stood up and brandished a noose at the scientist.

The incident led Schellnhuber to declare in an interview earlier this year that it was only a matter of time before deniers kill a climate scientist. Last year, several researchers at the Australian National University in Canberra, located in the southeastern part of the country, had to be relocated to a secure facility after they received a deluge of threats from skeptics.

Beyond the safety of the scientists, "the worrying thing is the message that is sent to the public," said Tremblay of McGill—that the science isn't settled when it is. "[The harassment] just serves to polarize the debate even further. People need to start speaking about this issue for what it is, and leave political and other agendas on the side."