GLOSSARY OF TERMS
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Greenhouse Gases (GHG)
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Greenhouse gases are a natural part of the atmosphere. They trap the sun's warmth, and maintain the earth's surface temperature at a level necessary to support life. The problem we now face is that human actions - particularly the burning of fossil fuels (coal, oil and natural gas) and land clearing - are increasing the concentrations of these gases, creating the prospect of global climate change. This is called the enhanced greenhouse effect.
The primary greenhouse gases arising from human activities are carbon dioxide, methane, nitrous oxide, perfluorocarbons, hydrofluorocarbons, and sulphur hexafluoride. Carbon dioxide concentration in the atmosphere is now about 1/3 higher than it was 200 years ago. This gas makes the biggest contribution to the Enhanced Greenhouse Effect (contributing 3/4 of all emissions). The burning of oil, coal and natural gas, and the clearing and burning of vegetation are mainly causing the increase.
Methane makes the next biggest contribution to global warming—around 1/5 of the total. Its concentration has risen by about 145% over the past 200 years. The digestive processes of cattle, rice cultivation, venting of natural gas, and waste decomposition in landfills are some of the major sources of methane emissions.
Nitrous Oxide: Burning vegetation, industrial emissions, and agricultural processes have contributed to an increase of about 1/7 in the nitrous oxide concentration in the atmosphere over the past 200 years. The phase-out of chlorofluorocarbons (CFCs) to protect the greenhouse gas levels should see concentrations steadily decline. Other halocarbons of greenhouse significance include per fluorocarbons (PFCs) emitted during aluminium production.
(From greenhouse.gov.au, greenhousegases.gov.au)
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