Hard Choices: Climate Change in Canada

4 Impacts of Climate Change in Canada

73 4 5 Impacts of Climate Change in Canada James P . Bruce and Stewart J. Cohen* * Opinions expressed in this chapter are those of the authors, and do not necessarily reflect the views of the Government of Canada. A s global emissions of greenhouse gases continue to soar, the world’s climate is changing ever more rapidly. Canada, being at northern latitudes where changes are expected to be greatest, has begun to feel adverse effects. Table 4.1 gives information about the changes affecting Canada to the end of 2000 and the projected changes into the present century.The latter are based mainly on the outputs of the Canadian Climate Model—an Atmosphere–Ocean General Circulation Model (Canadian aogcm). This model has predicted reasonably well the changes that have occurred in Canada to date (Boer et al., 1998). The Canadian gcm and most others include the effect of particles or aerosols in the air, which partly offset the greenhouse gas effect. In these model outputs, it is assumed that atmospheric greenhouse gas concentrations will continue to increase due to continued global increases in emissions (primarily from burning of fossil fuels). In a few cases in Table 4.1, the consensus projections of the Intergovernmental Panel on Climate Change (ipcc)1 2001 report are cited instead of Canadian model outputs. It must be recognized, however, that over the twenty-first century, the increase in emissions of greenhouse gases could have a wide range. If global economies, populations, and energy consumption from fossil fuels continue to increase at a rapid rate, carbon dioxide (CO2) emissions could be more than triple pre-industrial levels by 2100. However, if energy conservation and use of renewable energies increase, and reductions in rates of economic and population growth occur, CO2 emissions might increase only 25% by 2050. Bringing the Kyoto Protocol into force could start the 74 What’s [Going] to Happen[ing]? Table 4.1 Climate Change Projections and Observations for Canada Source : Data from Akinremi et al., 1999; Angel and Isard, 1998; Boer et al., 2000; Carnell and Senior, 1998; Gregory et al., 1997; ipcc, 2001; Karl et al., 1995; Lambert 1995; McCabe et al., 2001; Mekis and Hogg, 1999; Moore, 1996; Ross and Elliot, 1996; Sarnko et al., 2002; Stone et al., 2000; Zhang et al., 2000; Kharin and Zwiers, 2000. Notes: HadCM3 ⫽ Hadley Centre (UK) Climate Model version 3 2 ⫻ CO2 ⫽ doubled pre-industrial level of CO2 equivalent (by latter half of 21st century) cgcm ⫽ Canadian Global Climate Model (cccma) (Environment Canada, University of Victoria) ⫹⫹ ⫽ significantly more ⫹ ⫽ more Projected Observed to Date (2000) Global Mean Temperature 1.4–5.8ºC (1990–2100) ⫹0.6 or ⫺0.2ºC (20th century) Canadian Mean Temperature 2–4ºC (cgcm: 1975–95 to 2040–60) ⬎1ºC (20th century) Total Precipitation (2040–2060) 0 to 20% more in north slightly less in mid continent in summer (HadCM3) 1950–1998 ⫹⫹ at high altitudes, ⫹ at mid latitudes Southern Prairies little change Streamflow (or soil moisture) Mid-continent 30% by 2050 2⫻ CO2 (cgcm) ⫺10% Southern Prairies (1967–1996) Date of Spring Breakup Earlier Earlier: 82% of basins (1967–1996) Extreme Rainfall Years between heavy rain events reduced by half (2090) Up to 20% increase in heavy 1-day falls in US and se Canada (early summer) Water Vapour in Troposphere (lower atmosphere) Increase Statistically significant increase over N. America except ne Canada Mean Sea Level Rise 40–50 cm (mean ipcc projections) 1990–2100 10–20 cm (1900–1999) Arctic Sea Ice Extent ⫺21 to ⫺27% by 2050 ⫺3% per decade since 1978 (year round ice extent) Snow Cover Extent Dec., Jan., Feb. ⫺15% by 2050 N. America (cgcm) ⫺10% (1972–2000) Northern Hemisphere Late Season Snow Pack in Rockies —Apr. 1 Less (more melt over winter) 30% less since 1976 Fraser River Basin Glacier Retreat South of 60ºN e.g., Glacier National Park None left in Park (by 2030) 2/3 reduction in numbers in Park (from 150 to 50) (1850–1990s) Severe Winter Storms Frequency and Intensity 15% to 20% increase 2⫻ CO2 (cgcm) (1959–1997) • N of 60ºN Increased frequency and intensity • S of 60ºN Increased intensity world on this latter path. Uncertainty about future emissions is the largest source of uncertainty about climatic futures. Nevertheless, even with depressed world economies and a huge change in energy consumption patterns, atmospheric concentrations and rates of...