The Earth is a Greenhouse

A lot of people think that the atmosphere is just air. But it's more complex than that. It's actually a mixture of gases that surrounds the Earth, performing many functions and helping to support life on our planet.

Is the Earth a huge greenhouse?

As you know, greenhouses use glass to keep the heat in. And just as the glass in a greenhouse holds the sun's warmth inside, so the atmosphere traps the sun's heat near the Earth's surface. This keeps the Earth warm using what are called "greenhouse gases". Without these gases, the sun's heat would escape and the average temperature of the Earth would drop from 15 degrees Celsius to -18 degrees Celsius!

The greenhouse effect

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Gases in our atmosphere, including water vapour, carbon dioxide, methane, and nitrous oxide, act like a greenhouse to keep the sun's heat in and help make our planet livable. Without this natural insulation, the Earth's surface would be much colder than it is now. In fact, the average temperature on Earth would be -18° Celsius, too cold to support the diversity of life that now exists.

Enhancing the greenhouse effect

Since the Industrial Revolution, developed countries have produced increasing quantities of greenhouse gases, due to the burning of fossil fuels such as coal, oil, and natural gas to drive our vehicles, power our industries, and heat and cool our homes. Other human activities, such as the clearing of land for agriculture and urban development, and landfilling and other waste disposal methods, are also adding to the concentrations of greenhouse gases in our atmosphere.

As a result, concentrations of carbon dioxide in the atmosphere have increased by 31 per cent since 1895. Concentrations of methane and nitrous oxide, which are also related to human activities, have increased by 151 per cent and 17 per cent respectively during the same period. Increased concentrations of greenhouse gases in our atmosphere are enhancing the natural greenhouse effect, causing the Earth to become warmer.

In Canada, greenhouse gas emissions in 2000 were 15 per cent greater than they were in 1990. Canada accounts for just 2.5 per cent of global greenhouse gas emissions, but is the world's third largest per capita emitter of these gases, after the United States and Australia.

"There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities..."

Climate Change 2001: The Scientific Basis,
Intergovernmental Panel on Climate Change (IPCC)

In what ways do Canadians contribute to climate change?

We live in a large country with relatively few people and lots of miles between us; so we generally rely on our cars and trucks to move us around and to move our products from place to place. We also experience very cold winters, so we burn a lot of fossil fuels such as coal, oil or gas to keep our homes, offices and schools warm. We're lucky that Canada has abundant energy of all kinds, but we use much more energy than we really need.

SOURCE: Government of Canada