The Greenhouse Gases
What are the greenhouse gases (GHG) and how are they produced?
We know that our atmosphere is a complex mixture of gases that trap the sun's heat near the earth's surface, similar to how the glass of a greenhouse traps the sun's warmth.
The main greenhouse gases are:
- water vapour (H2O)
- carbon dioxide (CO2)
- methane (CH4)
- nitrous oxide (N2O)
- ozone (O3) and
- halocarbons (CFCs, HFCs, etc.)
Without these "greenhouse" gases, the sun's heat would escape and the average temperature of the earth would be 33 degrees cooler (-18° C instead of plus 15° C) – too cold to support life as we know it.
There are six greenhouse gases covered under the protocol to the international convention on climate change (the Kyoto Protocol) – carbon dioxide, methane, nitrous oxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6).
Carbon dioxide is the most important of the greenhouse gases released by human activities. It is the main contributor to climate change because of the quantities released – especially through the burning of fossil fuels. When fossil fuels are burned, the carbon content is oxidized and released as carbon dioxide; every tonne of carbon burned produces 3.7 tonnes of carbon dioxide. The global consumption of fossil fuels is estimated to release 22 billion tonnes of carbon dioxide into the atmosphere every year – and the amounts are still climbing.
Since the beginning of the Industrial Revolution, concentrations of carbon dioxide have increased by 31 per cent, and methane by 151 per cent.
Methane is produced naturally when vegetation is burned, digested or rotted without the presence of oxygen. Large amounts of methane are released by garbage dumps, rice paddies and grazing cattle. Methane is significant because it has 21 times the heat-trapping effect of carbon dioxide.
Nitrous oxide occurs naturally in the environment but human activities are increasing the quantities. Nitrous oxide is released when chemical fertilizer is used in agriculture.
Greenhouse gases and climate change
For thousands of years, the Earth's atmosphere has changed very little. The temperature and the careful balance of greenhouse gases have stayed just right for humans, animals and plants to survive. But today we are having problems keeping this balance. Because we burn fossil fuels to heat our homes, run our cars, produce electricity, and manufacture all sorts of products, we are adding more greenhouse gases to the atmosphere. These activities are changing the atmosphere at a greater rate than humans have ever experienced.
Human activities have resulted in the release of significant quantities of greenhouse gases, which remain in the atmosphere for long periods of time. This intensifies the natural greenhouse effect.