February 15, 2003
A study of snow accumulation on Canada’s highest mountain, in the Yukon Territory, suggested that significant climate change has occurred in western Canada over the past 150 years.
The study examined climate change over the past 300 years, concluded that both surface and atmospheric temperatures have risen in western Canada since the middle of the 19th century, and warned that if the trend continues, the region could see warmer winters and changes in weather patterns.
Along with researchers from the University of Calgary and the PAGES International Project Office in Bern, Switzerland, University of Toronto physicist Kent Moore studied snow accumulation on Mount Logan in the Yukon Territory. The snow accumulation record was found in an approximately 100-meter-long ice core drilled out of the mountain at over 5,300 meters above sea level. The ice core was extracted on the north side of the mountain directly behind the peak.
Chemical analysis of the ice core showed that between roughly 1700 and 1850, the average annual snow accumulation at the site remained constant. But starting around 1850, there has been a marked increase in snow accumulation, with the largest changes taking place in the past decade. “We argue that this increase in snow accumulation is associated with a warming of the atmosphere over western Canada,” said Moore.
Warmer air holds more moisture that can produce snow during winter.
Although the last century has seen an increase in surface temperatures in the region, the short length of atmospheric data sets, typically 50 years or less, has made it difficult to identify a similar trend in the atmosphere. Current theories and models require that both higher surface temperatures and atmospheric warming must exist for there to be evidence of climate change due to an increase in greenhouse gases. Moore said his team’s study provides this evidence.
A paper produced by the team noted two specific patterns of regional climate variability as possible causes of warming in western Canada — the Pacific North America pattern and the Pacific Decadal Oscillation. “We’re seeing evidence that both of these climate modes have been intensifying,” said Moore. “This is evidence that the atmosphere in the region has warmed up, and that it’s doing it through an intensification of some natural modes of climate variability.”
If this is a manifestation of regional climate change, Moore warned that these intensified modes may affect regional winter weather patterns. “Western Canada will continue to warm,” he said.
Previous research has shown that levels of atmospheric carbon dioxide — a major greenhouse gas linked to climate change — also began to rise in western Canada around 1850, due partly to the Industrial Revolution and land-clearing for farming.
Moore said the atmospheric warming findings refute the argument that climate change is not related to human activities.
Thanks to Nicolle Wahl and the University of Toronto.