|
| |
Greenhouse Gases
Greenhouse gases are infrared-absorbing natural or synthetic gases, which mainly find their way into the atmosphere through emissions, but also partially occur due to chemical reactions there.
Most greenhouse gases are trace gases, which make up less than 1% of the whole gas volume. |
|
Greenhouse gases that, according to the Kyoto Protocol (see History), need to be reduced:
carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), partially halogenated dichlorotetrafluoroethane (H-CFC/HFC), perfluorocarbons (CFC/PFC), sulfurhexaflouride (SF6) |
|
CO2 Carbon Dioxide
CO2 is the most important gas that causes an additional greenhouse effect (an approx. 50% share of the anthropogenic greenhouse effect). According to the IPCC report of 2001, an 31% increase in the concentration of CO2 in the atmosphere has taken place since 1750. Some 75% of anthropogenic CO2 emissions in the atmosphere over the last 20 years have their cause in the burning of fossil fuels.
Origins
 | Combustion of fossil fuels (oil, gas, coal). |
| Decimation of forests |
| Surface erosion (oxidation of the carbon stored in the earth) |
Quarrying
Ocean and plant life (above all large forests) extracts CO2 from the atmosphere (CO2 dips)
CH4 Methane
The concentration of methane in the atmosphere has risen by 151% since 1750 and is continuing to rise (IPCC report from 2001). Methane molecules possess large heat absorption capacity, i.e. small concentrations all have a great effect with regard to the greenhouse effect.
Origins
Methane occurs due to the bacterial decomposition of organic material under anaerobic conditions (when no oxygen is present). Natural sources:
| Wet regions (swamps) |
| Animals, for instance Termites (termites digest wood with the help of bacteria that create methane), bovines |
Anthropogenic sources:
| Rice fields |
| Livestock farming (the bacteria in the stomach of a cow produces around 100 l of methane a day) |
| Rubbish tips |
| The extraction and transport of natural gas |
| Coal mines |
| Manure heaps, liquid manure pits |
N2O nitrous oxide, laughing gas
Nitrous oxide effects the greenhouse effect more than 300 times more than CO2.
Origins
Nitrous oxide mostly occurs due to the microbial transformation of nitrogen present in the earth. The increase in N2O due to human influence takes place because of the increased nitrogen content in the earth that mainly results from agriculture, industry and transport.
Quarrying
Due to photochemical reactions in the stratosphere.
H2O Steam
With a share of up to 3%, steam is not one of the atmospheric trace gases. Due to its high concentration, it plays an important role in the natural greenhouse effect, although the water molecules only absorb a specific range of waves from the heat given out from the earth. Steam only stays for a short time in the atmosphere and returns to the earth in the form of precipitation.
CFC Fluorine chlorine hydrocarbons, fully halogenated hydrocarbon
CFC is a purely synthetic material that does not exist in nature. They do not just function as greenhouse gases, but, above all, are responsible for the break down of our "UV protection shield" in the stratosphere. Due to the measures taken up in the Montreal Protocol (see
History) their concentration has, thankfully, hardly risen since 1996, or is even becoming less.
CFC Sources
| Propellants in aerosols (spray cans), cellular and insulation material |
| Refrigerants in refrigeration units and refrigeration plant |
| Solvents and cleaning agents |
Break Up
Only by way of photolysis in the stratosphere, in which the chloratomes effect the break up of ozone.
CFC Partially halogenated fluorine chlorine hydrocarbons
HFC
Partially halogenated fluoro chloro hydrocarbons
FHC
Fluoro chloro hydrocarbons
PHC
Perfluorocarbons
They are largely used as replacement material for CFC, since they do not destroy the ozone layer. They do however function as greenhouse gases. Their concentration in the atmosphere is still rising partially at present.
SF6 Sulfurhexaflouride
This is a gas which is very slow to react, and for this reason is mostly used in high voltage plant in heavy industries and as a filler gas in sound insulated windows and car tyres. SF6 is the gas with the largest greenhouse potential. A tonne of SF6 burdens the atmosphere to the same extent as 23,900 tonnes of CO2.
O3 Ozone
Ozone accelerates the greenhouse effect and is also toxic in high concentrations and is contained in the lower troposphere (close to the earth). On the one hand it occurs naturally, but is also formed by photochemical reactions in the troposphere resulting from transport exhaust,.
Comment:
Above urban areas with high emission densities of nitrous oxide NOX, carbon monoxide CO and volatile organic compounds, relatively high ozone levels occur increasingly frequently when the sun shines intensely (high pressure weather in summer).
Ozone Layer: The ozone close to the earth, which intensifies the greenhouse effect, and which endangers the health of people as smog in summer, should not be mistaken for the ozone that exists in the atmosphere and which play a major role there for life on earth. As an ozone layer it forms a protective shield against the UV rays from sunlight.
[Author: Dipl.Biol. Marietta Enss, Edited by: Ragnar Müller]
[Top of Page]
|
