Gases
causing the Greenhouse Effect
Carbon dioxide (CO2): the gas principally responsible for the greenhouse effect. The percentage of carbon dioxide now present in the atmosphere is the highest for the last two hundred thousand years. It is produced in all energetic processes : _ of all carbon dioxide emissions derive from the combustion of fossil sources (oil and derivatives, coal, methane gas) while the remainder is principally due to deforestation. The different fuels behave in different ways: coal produces more CO2, while methane pollutes less.
Methane (CH4): mainly released during the processes of anaerobic digestion, such as occur in refuse dumps, in the fermentation of animal deposits, and in areas of irrigated cultivation (paddy-fields) or in damp areas. 15% of the emissions relating to methane are due to the activities of extraction and distribution.
Nitrous oxide (N2O) : originates predominantly from the agricultural sector, in particular from fertilisation and cultivation using azotic compounds.
Ozone (03) : that formed in the lower atmosphere as a result of chemical reactions between different pollutants, such as nitric oxides, carbon monoxide and unburnt hydrocarbons.
Chlorofluorocarbons (CFC3) : the same gases as are responsible for the so-called "hole in the ozone layer", that is for the rarefaction of the stratospheric ozone. As distinct from the climate-altering gases, the CFC are only produced artificially and are principally used in refrigerators, air-conditioners, insulating materials and solvents. Previously inexistent, they are now present in the atmosphere in percentages of up to 0.05 ppbv (parts per billion volume).
From "Italian City Councils against the Greenhouse Effect" - Italian Environment, Legambiente, Ministry for the Environment.
 | In collaboration with Ecosportello per il Risparmio Energetico e la Bioarchitettura Valle d'Aosta Region, Italy E-mail: ravdaec@tin.it |
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