Western Canada has warmed significantly over the past 150 years, scientists say.

Researchers studied a 103-metre ice core drilled from Canada's highest mountain, Mount Logan in the Yukon. They say the core shows surface and atmospheric temperatures have risen since the middle of the 19th century. University of Toronto physics Prof. Kent Moore, glaciologist Gerald Holdsworth of the University of Calgary, and Keith Alverson from Bern, Switzerland, chemically analysed the 300-year-old ice cap.

They found the average annual snowfall started to increase around 1850. "We argue that this increase in snow accumulation is associated with a warming of the atmosphere over Western Canada," Moore said in a release.

Southwest face of Mount LoganCourtesy: Gerald Holdsworth, University of Calgary

It may seem paradoxical for warmer temperatures to bring more snow, but Moore explained warmer air holds more moisture, which can fall as flakes.

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The increase in snowfall coincides with a time when farmers were clearing the land for agriculture and Western Canada was becoming more industrialized.

Earlier studies found levels of carbon dioxide, a greenhouse gas linked to global climate change, began to rise in Western Canada around 1850.

Two types of warming

The researchers pointed to evidence that the atmosphere in the region has warmed up by intensifying two natural patterns of regional climate variability.

Critics of earlier global climate change research have said surface temperatures suggested warming but atmospheric measurements did not.

The ice core results add to scientists' understanding of how atmospheric temperatures have changed over a longer time frame. Direct measurements only go back to the late-1940s.

The study, which appears in Thursday's issue of the journal Nature, said if the trend continues then Western Canada could continue to warm.

Researchers have warned that global climate change will increase the risk of droughts, floods and other natural disasters around the world.