A quintessentially Canadian winter tradition – outdoor ice hockey – could be facing extinction within decades because of climate change, a new study says.

Pick-up games of ice hockey, also called shinny or pond hockey, are a way of life during the long winters. Many towns are studded with neighbourhood ice rinks, some families even freeze over their backyards. Ottawa has the Rideau Canal, the 5-mile skate run through the nation's capital. But such pursuits are in peril as milder winters and earlier springs pare down the outdoor ice season.

The ice season has shortened noticeably over the last 50 years, especially in southern British Columbia and Alberta and parts of the prairie provinces, the study in the Institute of Physics' journal, Environmental Research Letters, says.

Temperatures are not staying low enough long enough to allow ice to freeze over.

By mid-century, it may no longer be possible to play ice hockey or skate on outdoor rinks without artificial intervention. "If you draw a straight line into the future you get zero rink-flooding days by mid-century which implies that at some point in that period you can't build a rink because it is not getting cold enough," said Damon Matthews, a geographer at Concordia University and author of the study.

That prospect might even be enough to alarm the prime minister, Stephen Harper, who has come under growing criticism in the international community and at home for reneging on Canada's commitment to cut greenhouse gas emissions, and for his aggressive promotion of the Alberta tar sands, which have a heavier carbon imprint than traditional crude.

"I think this is going to strike a chord with Canadians," Matthews said. "When I think of things that are vulnerable to climate change that people care about in Canada I would place outdoor ice hockey very close to the top of that list."

It takes a long cold spell to be able to build a good foundation for ice sports – at least three days in a row at -5C, the researchers determined, from interviews with public rink officials.

But temperature records from 142 weather stations across the southern belt of Canada, where most of the population lives, showed a distinct warming trend from 1951-2005.

According to the criteria set by rink officials, many of those locations would have experienced later start dates for outdoor skating over the years. Most showed shorter seasons, as much as 20 to 30% shorter in British Columbia, Alberta, Saskatchewan, and Manitoba and parts of western Ontario. Only Atlantic Canada showed a longer season.

"We would expect all regions of Canada to see a decreased viability of outdoor skating under continued winter climate warming," the paper says. In the most extreme case of the southwest Canada region ... the number of viable rink flooding days could reach zero by mid-century."

The results should not be surprising, said Simon Donner, a climate scientist at the University of British Columbia. Temperatures in Canada have increased by more than 2.5C since 1950, which is about three times the global average of warming attributed to climate change.

Canadian cities are becoming warmer because of increasing urbanisation, but there is no missing the evidence on the ground of climate change. "The study gels very much with the observations we have for changes in ice," Donner said. "This is a theoretical result but we have observations from across Canada showing that the length of time that lakes would remain frozen during the winter has been decreasing, so it follows from that."