Skates and hockey sticks on backyard rinks are the definitive sound of winter for many Canadians.

But Robert McLeman, a professor of geography and environmental studies at Ontario's Wilfrid Laurier University, warns that climate change is having a serious effect on this traditional pastime.

"In the old days when I was a kid, you just flooded straight onto the snow that was packed into the ground," McLeman said.

"But the ground doesn't freeze as solid as it used to. If you get one of these little t…