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Information identified as archived is provided for reference, research or recordkeeping purposes. It is not subject to the Government of Canada Web Standards and has not been altered or updated since it was archived. Please "contact us" to request a format other than those available.
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ContextNaturally occurring greenhouse gases, mainly carbon dioxide, nitrous oxide, methane and water vapour, help regulate the Earth’s climate by trapping heat in the atmosphere and reflecting it back to the surface. Over the past 200 years, increased atmospheric concentrations of greenhouse gases resulting from human activities such as burning fossil fuels (oil, coal and natural gas) and deforestation have amplified this natural process, and scientists predict that this trend will continue (Environment Canada 2006a). Global atmospheric concentrations of carbon dioxide are now about 31% greater than in pre-industrial times, and global average temperature has increased by 0.8°C since the start of the industrial revolution. Canada has seen a rise in average temperature of about 1°C since 1950, with six of the warmest years on record in Canada occurring during the last decade (Mehdi 2006). Emissions of greenhouse gases have been estimated by scientists and governments for more than a decade. In 1988, the Intergovernmental Panel on Climate Change (IPCC) was established by the United Nations Environment Programme and the World Meteorological Organization to investigate climate change. The panel concluded that a doubling of greenhouse gas concentrations in the atmosphere would lead to serious consequences for the world’s social, economic and natural systems (Houghton et al. 1990). It estimated that a doubling of carbon dioxide levels would lead to an average global temperature increase of 1.4°C to 5.8°C by 2100 (IPCC 2001). A warming of this speed and magnitude could significantly alter the Earth’s climate, causing severe storm patterns, more heat waves, changes in precipitation and wind patterns, a rise in sea level and regional droughts and flooding. A general warming trend could also affect forest distribution around the world and the length of the growing season for crops. Although an extended growing season might yield some economic benefits in northern countries like Canada, indigenous species would have little time to adapt to a warmer climate and would likely have to cope with more extreme events, such as forest fires, and with increased stress from invasive, exotic species and diseases. In Canada’s north, permafrost can be expected to melt, with implications for infrastructure such as buildings and highways, and the extent of Arctic sea ice can be expected to decline, which will affect northern travel and traditional hunting practices. Loss of sea ice will also amplify the warming effect, because seawater reflects less solar radiation than ice. On a national basis, agriculture, forestry, tourism and recreation could be affected, as could related supporting industries and towns. Climate change is also projected to impact human health by leading to an increase in cases of heat stress, respiratory illnesses (e.g. asthma) and transmission of insect and waterborne diseases (e.g. malaria), thereby placing additional stresses on health infrastructure and social support systems. The greenhouse gas emissions indicator focuses on total national emissions of the six main greenhouse gases (Box 3). Box 3. The greenhouse gas emissions indicator The national greenhouse gas emissions indicator comes directly from the National Inventory Report: Greenhouse Gas Sources and Sinks in Canada (Environment Canada 2006a), which contains emissions estimates for sources categorized by economic sector as identified by the IPCC. It includes estimates for six greenhouse gases: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulphur hexafluoride (SF6), perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs). The land use, land-use change and forestry sector is excluded from the greenhouse gas totals constituting the indicator. The emissions estimates and sector definitions used for reporting are based on methodological guidance provided by the IPCC and reporting guidelines under the United Nations Framework Convention on Climate Change (UNFCCC). The estimates for each sector are generally calculated by multiplying a measure of the amount of greenhouse gas-producing activity by the quantity of greenhouse gases emitted per unit of activity (e.g. carbon dioxide released per litre of gasoline combusted). Emissions estimates for different gases are converted to their equivalent in carbon dioxide, based on their impact on global warming compared with carbon dioxide. All greenhouse gas emissions are expressed as megatonnes (million tonnes) of carbon dioxide equivalent (Mt CO2 eq), unless otherwise noted. A more detailed description of the indicator and how it is calculated is provided in Description of the greenhouse gas emissions indicator. The complete National Inventory Report: Greenhouse Gas Sources and Sinks in Canada (Environment Canada, 2006a), is available at (www.ec.gc.ca/ghg).
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