What are Greenhouse Gases

Monday, 22 August 2011 13:13 | Written by Tanya

Greenhouse Gases

The Earth's atmosphere is made up of layers of gases, some of which are known as 'greenhouse gases'. They are predominantly natural gases which make up a "thermal blanket" over the earth, trapping enough of this heat in the atmosphere, and letting some of the rays go back out of the atmosphere into space.

This keeps the earth at the correct temperature for humans, animals and plant to survive. The overall average temperature of the Earth is 15/16°C. So the correct balance of greenhouse gases ensures the survival of our planet, and allows for conditions that provide us with air to breathe, fresh water and the weather our survival depends on. (Without these gases, the average temperature would be about minus 18°C!)

The "greenhouse effect" is the warming that happens when certain gases in the Earth's atmosphere trap heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse.

Greenhouse gases are natural gases made out of:

The two major gases:

• water vapour

• carbon dioxide (CO2)

The lesser gases:

• methane

• nitrous (nitrogen) oxide

• ozone

• chlorofluorocarbons (CFCs)

The ozone layer is made up of ozone (a type of oxygen) that protects the earth from too many harmful rays called UVB.

The respiration of animals, volcanic eruptions and decaying plants discharge natural CO2 into the Earth's atmosphere, where it exists for about 100 years.

It is eliminated from the atmosphere by plant photosynthesis and by dissolution in water (such as in the oceans). This natural carbon dioxide cycle keeps a balance in the amount of CO2 in our atmosphere. But human actions and behaviours can cause changes which upset this natural balance.

When too many greenhouse gases are created, the "thermal blanket" thickens and too much heat is trapped in the Earth's atmosphere, increasing the overall average temperature - which has a number of devastating consequences. See below.

Extra greenhouses gases are produced by humans by our creation of pollution through activities such as burning coal and petrol (referred to as 'fossil fuels' or fossil energy)( e.g. power plants, factories and exhaust from cars); the destruction of rainforests and cutting down of other forests; and methane produced by animal waste. Like a circuit board that will blow if overloaded, we are in the process of overloading our atmosphere with heat-trapping gasses!

There is scientific agreement that our Earth's atmosphere is warming and emissions of greenhouse gas pollutants are contributing to that warming. Our Earth will continue to get warmer as the quantity of these pollutants keep on building up in the atmosphere.

Although we cannot stop global warming, we can make lifestyle and industry choices that can slow it down and lessen the effects.

We need to slow down our use of fossil energy, in particular coal.

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