If you don't like the climate ... wait a while

Warming and cooling trends are part of the Earth's normal climatic cycles. Temperatures vary within a given year, from one year to the next, and on longer time scales, over decades, centuries, and millennia. In fact, there have been frequent changes in climate, with repeated swings from colder to warmer conditions. Past changes in climate have had significant impact on human development. At the peak of the last ice age (about 16 000 years ago), most of Canada was covered with ice.

After the Ice Age: the last 10 000 years

Global temperature change in the last 10 000 years (Folland et al., 1990)

The global climate warmed rapidly at the end of the last ice age. By about 4000 BC, the Prairies were warm and dry, and prairie grasslands probably extended more than 80 km farther north than they do today. Later, increased moisture and cooler temperatures caused renewed glacier ice accumulation in the Rockies.

Warmer - cooler - hotter the last 1000 years

the last 1000 years (Mann et al., 1999)

During the Medieval Warm Period, between about AD 1000 and AD 1200, temperatures were comparatively warm - this is the time when Vikings travelled to Greenland and Newfoundland. During a subsequent cooling trend called the Little Ice Age, the Vikings abandoned their settlements, Europe experienced colder weather, and the glaciers in the Rockies expanded again. By AD 1860, temperatures began to rise again.

Turning up the heat in the 1980s and 1990s

the last 140 years (Environment Canada, 1993)

Over the past 140 years, Earth's atmosphere has warmed. Since the 1980s this warming trend has increased. Scientists are concerned that we are entering a period of unprecedented global warming caused by human activity.

Did you know?
The twentieth century was the warmest century of the last 1000 years, and the 1990s was the warmest decade of that century.

A much different future

This map shows predicted summer surface air temperature change for the northern hemisphere that could occur in the next century. The greatest differences are predicted to occur in the Arctic and the interior of North America.

Projected changes in the summer temperatures for 2080-2100 relative to 1975-1995 (Source: Canadian Centre for Climate Modelling and Analysis, Environment Canada, pers. comm. 2000)

References

Environment Canada, 1993: A matter of degrees: a primer on global warming; The Environmental Citizenship Series, Environment Canada, Ottawa, Ontario, 89 p.

Folland, C.K., Karl, T.R., and Vinnikov, K., 1990: Observed climate variations and change; in Climate Change: the IPCC (Intergovernmental Panel on Climate Change) Scientific Assessment, Cambridge University Press, London, United Kingdom, p. 195-238.

Mann, M.E., Bradley, R.C., and Hughes, M.K., 1999: Northern hemisphere temperature during the past millenium: inferences, uncertainties, and limitations; in Geophysical Research Letters, v. 26, no. 6, p. 759-762.