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The current scientific consensus is that Earth's climate in the twenty-first century will not be the same as it has been in recent history.


Atmospheric CO2 Concentrations (Turner and Clague, 1999)

Atmospheric CO2 Concentrations
(Turner and Clague, 1999)

Although a number of uncertainties about the rate and timing of change remain, the fact is that Earth is experiencing a warming trend. The average global temperature has increased by approximately 0.5°C over the past 100 years. In Canada, the average temperature has increased by 0.9°C since 1948.

Upsetting the balance

Primarily as a result of our use of fossil fuels, human activities over the last 100 years have increased the amount of greenhouse gases in the atmosphere. This 'enhanced' greenhouse effect has the potential to warm the planet at a rate never before experienced in human history.

Ontario's climate in the twenty-first century

Scientists now estimate that Ontario will warm an average of 2°C to 5°C within the next 75 to 100 years. Temperature increases will be greater in the winter than in the summer and that the frequency and severity of extreme weather events are likely to increase.

Did you know?
Venus has an atmosphere that is 98% CO2. Due to the extreme greenhouse effect, temperatures reach 430°C. Similar conditions would exist on Earth if all the carbon stored in rocks and vegetation was released as CO2.

Modelling future climate

Projected Temperature Change between 1975-1985 and 2040-2060 (Hengeveld, 2000)

Projected Temperature Change between 1975-1985 and 2040-2060
(Hengeveld, 2000)

Powerful computer simulations called general circulation models or global climate models (GCMs) are the primary tools for estimating the future climate. These models are complex mathematical approximations of processes that underlie the global climate system. The complex elements of the climate system - such as oceans, land masses, the atmosphere, ice and snow, and many other influencing factors - are reproduced by the GCM. The model then allows scientists to estimate future conditions based on the manipulation of various elements of the climate system within the model.


Environment Canada, 1998: Climate change; National Environmental Indicator Series; State of the Environment Bulletin No. 98-3.

Hengeveld, H.G., 2000: Projections for Canada's climate future: a discussion of recent simulations with the Canadian Global Climate Model; Environment Canada, Climate Change Digest 00-01, 27 p.

Smith, J.V. , Lavender, B., Auld, H., Broadhurst, D., and Bullock T., 1998: Adapting to climate variability and change in Ontario; Volume IV of the Canada Country Study: Climate Impacts and Adaptation; Environment Canada, 117 p.

Turner, R.J.W. and Clague, J.J., 1999: Temperature rising: climate change in southwestern British Columbia; Geological Survey of Canada, Miscellaneous Report 67.

Future climate