INTRODUCTION
Human activities release air pollutants, most of them by-products of our use of fossil fuels — coal, oil and natural gas — to provide mobility, heat, industrial production, and wealth for regions which produce these resources.
About 90 per cent of the world's commercially produced energy, and about 70 per cent of Canada's, comes from fossil fuels. The
World Energy Outlook (OECD, 1998) forecasts global energy demand will grow by 65 per cent and CO2 will increase by 70 per cent between 1995 and 2020, unless new policies are put in place.
As fossil fuel use continues to rise, the consequences become ever more costly. Greenhouse gases from fuel combustion accumulating in the atmosphere continue to raise global temperatures. The increases are greatest in northern latitudes, including Canada.
The effects of climate change are numerous [see below] and while we may have some benefits from warmer temperatures, we will also face a number of costs.
Canada, along with many other nations, has signed the United Nations Framework Convention on Climate Change which includes a commitment to reduce emissions of greenhouse gases. Like most other nations, it has failed to curb pollution increases. This pollution is closely linked to economic development and increased personal consumption of energy, particularly through the growing use of larger motor vehicles.
Moving to more sustainable forms of development will require more efficient use of energy and a shift to sources of energy that have fewer harmful side effects.
Greenhouse gases act like a one-way mirror in the atmosphere, letting in much of the sun's light but trapping some of the infrared heat radiated by Earth. For millions of years, natural greenhouse gases have made our planet 33 degrees Celsius warmer than it would otherwise be, and thus able to support life as we know it.
Earth's climate is a fundamental part of our life support system. It shapes the way we can live on this planet. Yet the way we live, work and play is inadvertently changing the climate. 
A warmer atmosphere is more active, prone to weather extremes, such as floods, droughts and violent storms such as tornadoes and hurricanes. Warmer weather also brings ecological changes, moving species, including insect pests and disease-carrying organisms, further north. Hotter summers produce a variety of stresses and changes in the natural water cycle accompanying climate change will affect farmers, hydroelectric producers, tourist operators and many others.
Greenhouse gases
Since the mid-1800s, carbon dioxide concentrations (which account for about 75 per cent of the enhanced greenhouse effect caused by human activities) have increased by more than one quarter. Most of that increase was in the past half century.
The Intergovernmental Panel on Climate Change predicts that if current trends in fossil fuel use are not changed, in this century CO2 levels in the atmosphere will double from those before the industrial revolution causing a rise in global temperatures unprecedented in 10,000 years.
Emissions grew by 13 per cent from 1990 to 1997 and continue to rise. By 2010, emissions are projected to be 105 megatonnes (19 per cent) higher than in 1990. By 2020, they are projected to be 203 megatonnes (36 per cent) higher. The primary sources of these increases are population and economic growth, coupled with low energy prices and a shift to fossil fuels, particularly, natural gas, for electricity generation.
Canada's emissions of greenhouse gases
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PressuresEXTERNAL LINKS
UN Framework Convention on Climate Change
Environment Canada
2. Greenhouse Gases Background
3. Environmental Priority - Climate Change
4. The Greenhouse Gas Emissions Outlook to 2020
5. Canada's Greenhouse Gas Emissions by sector
Geo-2000: Global Environment Outlook, climate section