MONTREAL -- A tenured Mcgill University professor has resigned because of the school's failure to sell its stocks and investments in fossil fuels.

The professor, Gregory Mikkelson, has taught environmental ethics and philosophy for 18 years, but it felt wrong to stay on, he said, when he disagreed with McGill's action on environmental issues.

"When our board decided for the third time in seven years to defy the overwhelming democratic mandate that has developed for that divestment here on campus, I just decided to look for an organization that is both more democratic and more sincerely committed to saving the planet," he said on Tuesday.

In a statement, the university insisted it was reducing the overall carbon footprint of its investment portfolio, including its investments within the fossil fuel industry.

Mikkelson, however, said those goals are too vague.

"Whereas divestment would have been a clear and courageous commitment, decarbonization is a complex and confusing motion," he said.

On-campus Tuesday, students supported the Mikkelson. He had stood up for what he believed in, one said.

"All my teaching and research is telling us we need to do this [divest]," Mikkelson said, "and yet the organization I work for is telling me to do the opposite."