Enhanced Greenhouse Effect The earth's surface is surrounded by a blanket of gases in the atmosphere. The atmosphere acts in the same way windows of a closed car do when sitting in the sun. It allows most of the light to pass through which then reaches the earth's surface and is absorbed and converted into heat energy. This heat energy is re-emitted by the earth, but is trapped by gases in the atmosphere known as greenhouse gases.

Global warming, climate change, ozone depletion, sea level rise, biodiversity are all affected, one way or another, directly or directly, by harmful 'greenhouse' gases. A number of human activities, processes and consumptions produce waste gases that are harmful to the environment. They include: Fuel combustion Energy industries Manufacturing industries and construction Transport Fugitive emissions from fuels Solid fuels Oil and natural gas Mineral products Chemical industry Metal production Production of halocarbons and sulphur hexafluoride Consumption of halocarbons and sulphur hexafluoride Solvent and other product use Enteric fermentation Manure management Rice cultivation Agricultural soils Prescribed burning of savannas Field burning of agricultural residues Solid waste disposal on land Wastewater handling Waste incineration

Much of these harmful gases, natural and man-made, were targeted for reduction during the recently concluded COP3 conference in Kyoto. A brief description and effects of six gases are given below:

| Carbon Dioxide | Nitrous Oxide | Methane | Hydrofluorocarbon gases | Perfluorocarbons | Sulphur Hexafluoride |

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Carbon dioxide (CO2):
A naturally occurring gas produced by living organisms and fermentation, CO2 is also produced by the combustion of carbonaceous fuels. A normal component of the breath we exhale, it is hazardous in concentrated volumes.

CO2 emissions from fuel burning, responsible for about 87 percent of global warming, have increased by about 27 percent since the industrial revolution.

Global CO2 production from fuel burning in 1995 was about 22 billion tonnes.

| Carbon Dioxide | Nitrous Oxide | Methane | Hydrofluorocarbon gases | Perfluorocarbons | Sulphur Hexafluoride |

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Nitrous Oxide (N2O):
naturally occurring from microbial action in soil, N20 is also produced by fuel burning. Scientists say its production is increased by the use of nitrogen based fertiliser in agriculture, as well as by the use of catalytic converters in automobiles.

Global Warming Potential: 170 to 190 times greater than that of CO2.

| Carbon Dioxide | Nitrous Oxide | Methane | Hydrofluorocarbon gases | Perfluorocarbons | Sulphur Hexafluoride |

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Methane:
A naturally occurring, flammable gas, methane is caused by geological coal formations and by the decomposition of organic matter. Leading man-related sources are landfills; livestock digestive processes and waste, especially ruminants (cud-chewing animals); and wetland rice cultivation.

Global warming potential: About 24 times higher than that of CO2.

| Carbon Dioxide | Nitrous Oxide | Methane | Hydrofluorocarbon gases | Perfluorocarbons | Sulphur Hexafluoride |

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Hydrofluorocarbon gases (HFC) :
Man-made specialty gases developed as an alternative to ozone-eating chlorofluorocarbons (CFC), the coolant, cleaning, and propellant gases were blacklisted internationally in 1987. Because they do not possess chlorine, HFCs do not directly destroy ozone in the earth's atmosphere. They do, however, contribute to global warming. Principle uses: refrigeration; as agents used to blow foams or insulation; solvents or cleaning agents, especially in semi-conductor manufacturing.

Global warming potential: 4,000 to 10,000 times that of CO2.

| Carbon Dioxide | Nitrous Oxide | Methane | Hydrofluorocarbon gases | Perfluorocarbons | Sulphur Hexafluoride |

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Perfluorocarbons (PFC), or Perfluorocompounds:
Man-made replacement gases for CFCs but result also as a by-product of aluminium smelting. PFCs also used as a purging agent for semi-conductor manufacture and small amounts are produced during uranium enrichment processes.

Global warming potential: 6,000 to 10,000 that of CO2.

| Carbon Dioxide | Nitrous Oxide | Methane | Hydrofluorocarbon gases | Perfluorocarbons | Sulphur Hexafluoride |

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Sulphur Hexafluoride (SF6):
Very low atmospheric concentration makes it an ideal test gas for gas concentration monitors. Principle uses: insulating material for high-voltage equipment like circuit breakers at utilities. Also used in water leak detection for cable cooling systems. SF6 is a man-made gas.

Global warming potential: 25,000 times that of CO2.

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Sources: U.S. Energy Intelligence Agency, International Energy Agency, Intergovernmental Panel on Climate Change.