Recent climate-health studies suggest that some Canadian cities (e.g. Toronto and Montreal) could experience heat-related mortality during heat waves under the present climate. Furthermore, summer mortality rates would be expected to rise significantly in these locales as a result of climate change, and the projected increase in the frequency and intensity of heat waves.
The severe heat wave of July 1995 in the northern U.S. Great Plains, causing hundreds of deaths in Chicago and Milwaukee, was also observed in the Canadian Great Lakes region and other parts of eastern Canada, but with somewhat reduced intensity. However, Canadian death rates during and after the heat wave, as well as during the whole unusually warm summer of 1995, were not significantly different from normal. It is suggested that accessible air-conditioned facilities, e.g. nursing homes, and Canada-wide public health-care system outweighed the effects of the hot weather.
Analysis of a long record of mortality statistics shows a very pronounced seasonal pattern, with highest rates in winter and lowest rates in summer. The excess in winter deaths is due to cardiovascular diseases and pneumonia and influenza. Canada’s present climate is characterized by long and cold winters. However, GCM climate change scenarios (for a doubling of CO2) suggest a much greater warming in winter than in summer, in mid and high latitudes. Therefore, based on temperature variations only, climate change would be associated with a significantly reduced winter mortality, thus offsetting any potential increase in heat-related summer mortality.