Climate change will affect most aspects of our lives in Canada. Our economic, social and general well-being are all linked, both directly and indirectly, to climate. For example, climate influences the crops we grow, the productivity of our forests, the spread of disease, the availability of water, the health of ecosystems and the stability of our infrastructure. Changing climate brings many new challenges and, with them, the need to re-examine long-standing practices and assumptions.
Our climate is characterized by high variability, on both seasonal and annual scales. Although our economy, health and infrastructure are generally well adapted to current climate conditions, our vulnerability to climate is clearly evidenced by the impacts resulting from extreme weather and climate events. Losses from recent individual weather-related disasters in Canada are often in the hundreds of millions of dollars. Consider, for example, costs associated with the 2003 summer wildfires in British Columbia and Alberta ($400 million; Public Safety Canada, 2005), the 1991 and 1996 hailstorms in Calgary ($884 million and $305 million, respectively; Public Safety Canada, 2005), the 1997 Red River Flood ($817 million; Public Safety Canada, 2005) and 2003 Hurricane Juan in Halifax ($200 million). Multibillion dollar disasters also occur, including the 1998 ice storm in eastern Canada ($5.4 billion) and the Saguenay flood in 1996 ($1.7 billion; Public Safety Canada, 2005). The 2001 -2002 droughts, which were national in scale, resulted in a $5.8 billion reduction in gross domestic product (Wheaton et al., 2005). Extreme weather and climate events impact the health and well-being of Canadians beyond monetary costs, as they frequently involve displacement, injuries and loss of life. For example, the 1998 ice storm led to the greatest number of injuries (945) and 17 800 evacuations (Public Safety Canada, 2005). Unusually heavy rainfall following a period of drought was a contributing factor to the E. coli outbreak in Walkerton, Ontario in 2000 that resulted in seven deaths and thousands of people becoming ill (O 'Connor, 2002).
Increases in temperature and changes in precipitation have been observed across most of Canada over the past century. During the past 50 years (1948-2006; the period for which data are available for both northern and southern Canada), average national temperature has increased 1.3 °C (see Chapter 2; Environment Canada, 2006). This is more than double the increase in mean global surface temperature during the same time interval. Canada is projected to continue to experience greater rates of warming than most other regions of the world throughout the present century (see also Chapter 2; Environment Canada, 2006). The magnitude of changes in climate will vary across the country, with northern regions and the south-central Prairies warming the most (Figure 2). Average annual precipitation is also projected to rise, although increases in evaporation and transpiration by plants in some regions are expected to more than offset increases in annual precipitation, resulting in increased aridity. More frequent heavy precipitation events, less precipitation during the growing season and more precipitation during the winter are also projected for Canada
