The state of Canada's climate: Temperature change in Canada 1895-1991

Changes in average annual temperature between 1895 and 1991 were analyzed for 131 stations across the country to determine both national and regional temperature trends. Nationally, the country has warmed by a statistically significant 1.1°C over the period of study, although the warming has not been consistent throughout the entire time span. Three distinct phases are apparent in the national temperature record: a warming from the 1890s to the 1940s, a cooling from the 1940s to the 1970s, and a resumption of warming from the late 1970s on. The 1980s were indisputably the warmest decade on record in Canada, with the 1940s in second place, and the 1930s in third. Five of the last twelve years (from 1980 to 1991) rank among the warmest twenty-five of the past century. Regionally, temperature changes have varied from a moderate cooling of 0.6°C around Baffin and Ellesmere Islands to a substantial warming of 1.7°C in the Mackenzie District. With the exception of the Baffin and Ellesmere Island area, all regions of Canada have shown some degree of warming, although the trends have not been statistically significant in all areas. The warming shows most strongly in central Canada, in a broad band running from northwest to southeast through the Mackenzie District and the Prairie Provinces. It is less pronounced but still significant farther east in the Great Lakes Basin/St. Lawrence Lowlands and in the Shield country of Ontario and Quebec. It is weakest on the country's Atlantic and Pacific edges and in most areas of the Arctic. The warming that has been observed in Canada over the past century is unquestionably real and significant, though its intensity has varied from decade to decade and from region to region. Canadian temperature trends are similar to those that have been observed globally, both in the general magnitude of warming and in the variability of the temperature patterns. The increase in Canadian and world temperature averages is consistent with predictions of global warming as a result of an enhanced greenhouse effect. However, these increases are still within the limits of natural variability and cannot yet be attributed unequivocally to greater greenhouse warming.