The earth's average temperature has risen by more than 0.5 degree Celsius over the past 150 years. Some computer models predict that it might increase by another 1 to 3.5 degrees in a century given predicted increases in greenhouse gas emissions.
A warming of this magnitude could significantly alter the Earth's climate. Storm patterns and severity might increase, a rise in sea level would displace millions of coastal residents, regional droughts and flooding could occur.
A number of changes have been observed already, including melting glaciers and ice caps, a rise in sea levels and a number of violent storms, all consistent with an increasingly warmer world.
A large number of effects of global warming are predicted.
Global sea levels are expected to continue rising, threatening low-lying islands and deltas inhabited by hundreds of millions of people. Climate zones are predicted to shift towards the poles by 150 to 550 km in the mid-latitudes. Forests, deserts, rangeland and other ecosystems would face new climatic stresses, as would human societies, health and infrastructure.
Arctic and central Canada are already showing signs of a temperature increase, accompanied by thinner ice, retreating glaciers, shorter winters, some increased storms, drought and flooding, the kind of weather extremes expected with a warmer and more active atmosphere.
Human health is threatened
Productivity at risk
Great Lakes ecosystem
Global level
Canada
A federal study warned that Toronto, Montreal and Ottawa, known for their hot, humid air masses in summertime, would be most affected. People with heart disease, respiratory conditions, the elderly, the very young, the poor and the homeless would suffer most.
Increased temperatures will change rain and snowfalls as well as evaporation, leading to less predictable growing conditions. Canada's agriculture, forestry and energy sectors could all be significantly affected.
The Great Lakes are vulnerable to the effects of climate change, including a predicted drop in lake levels. This would affect shipping, hydro-electric power generation, drinking water supplies and recreation. Lower water levels would also affect wetlands and other wildlife habitat.
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UN Framework Convention on Climate Change
Environment Canada
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Geo-2000: Global Environment Outlook, climate section