Climate Change
Climate change is long-term changes to weather patterns over periods of time that range from decades to millions of years. It can be a change in the average weather conditions, or in a change of the distribution of events like more or fewer extreme weather events. Long-term changes in atmospheric temperature are largely due to the greenhouse effect.
The earth continually receives short-wave radiation from the sun, part of which (about 30 per cent) is directly reflected back into space by clouds, other material in the atmosphere and the Earth's surface, especially where it is covered by snow or other light-coloured material. The rest, about the energy equivalent of several light bulbs per square metre, is absorbed by the Earth.
The Earth, having been warmed, emits long-wave radiation back into space, but this radiation does not pass easily through the atmosphere and creates a layer of warmth next to the Earth's surface. This is termed the greenhouse effect.
The greenhouse effect is essential to life on earth. Without its warming effect, the earth would be cold and inhospitable.
The main greenhouse gases are nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2).
The Greenhouse Effect
Figure is a simplified sketch of a landscape including water, land with vegetation, clouds and the sun. Short-wave solar energy entering the earth's atmosphere is either reflected by clouds or absorbed by the earth's surface. The warmed surface re-emits long-wave energy back out of the earth's atmosphere. The greenhouse gases CO2, N2O and CH4 can absorb long-wave energy before it leaves the earth atmosphere and re-emit it as heat energy.
The greenhouse effect, therefore, arises because of the difference between the sun's radiation, called short-wave radiation, which passes through the GHGs, and the Earth's radiation, called long-wave radiation, which does not.
Increasing concentrations of the GHGs, however, could lead to an enhanced greenhouse effect, causing changes to our climate.
Human activities, such as burning fossil and solid fuels, and agriculture, have an effect on the climate through the emission of greenhouse gases. Agriculture production covers 68 million hectares of land across Canada. That vast scale of agriculture land use and crop and livestock production activities produce about eight per cent of Canada's greenhouse gas emissions, which affect both air quality and climate.
Conversely, crop and livestock production are also highly affected by weather and the impacts of climate change.
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This section contains information that is related to climate change and its relationship to agriculture. Additional information on climate change is also available on the Environment Canada Web site.