Experts say zombie fires, or fires that burn through Canada’s northern winter, were once thought to be folklore, but a recent study says they’re becoming more common as temperatures increase.

James Waddington, a professor at McMaster University’s school of Earth, environment and society, says a zombie, or a holdover fire, is one that comes back to life from a previous season after smouldering under the snow.

A recent report in the science Journal Nature says increasing summer temperatures associated with climate warming may promote the survival of overwintering fires.

Waddington says the fires are seen in the sub-Arctic, Arctic, Northwest Territories and northern parts of the boreal forest in Ontario, Alberta and Saskatchewan where peat is found in large amounts.

Mike Flannigan, a professor of wildland fire at the University of Alberta, says holdover fires also emit a lot more carbon on average than normal forest fires because peatlands are carbon reservoirs.

He says he would attribute most of the increase to the holdover fires to Canada’s warming climate.