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The Issue

Greenhouse gases consist of a series of gaseous compounds, and include water vapours, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulphur hexafluoride (SF6), and chloro-fluorinated hydrocarbons (PFCs, HFCs, CFCs). 

The greenhouse effect is a natural process, whereby the gaseous compounds mentioned above lead to the earth’s temperature remaining at higher levels than would occur if the gases in question did not exist. The mechanism is similar to that of a simple greenhouse (hence the name), where the glass or clear plastic ceiling, helps in keeping the interior warm even on cold days, by preventing heat losses. In the greenhouse effect, the gaseous compounds have the capacity to absorb and re-emit the heat emitted from the earth, which helps in maintaining the temperature on the earth’s surface at the levels necessary to preserve life in the diversity that has existed for centuries.

Without the presence of the greenhouse gases, the earth’s temperature would be about 33ºC lower, and the natural environment as we know it today would probably be very different. This result is achieved when the concentration of greenhouse gases in the atmosphere is kept at very low levels, and below certain limits. It is now widely accepted that as their concentration increases, the temperature on the earth’s surface also rises, thus leading eventually to global warming.

The concentration of one particular greenhouse gas, carbon dioxide in this case, has now increased to more than 380 ppm (parts per million), compared with 280 ppm in the pre-industrial era. During the last century (20th), the temperature on the earth’s surface rose by about 0.6ºC. The Intergovernmental Panel on Climate Change (IPCC) is forecasting further temperature rises, at a rate of 0.2ºC per decade. Other authorities are predicting even greater increase rates, up to 0.5ºC per decade, so that at the end of this century, the temperature may be between 2º and 5ºC higher than it is today. 

It is generally accepted that the upward trend of the planet’s temperature will lead to climate change, although the exact consequences of such a change are not yet known. The potential consequences are in any case catastrophic, whether it is a matter of an increase in the frequency and intensity of extreme weather conditions such as heat waves, droughts, floods and hurricanes, or a rise in sea levels as the glaciers and polar ice-caps melt, or the extensive destruction of various ecosystems and the extinction of many species of flora and fauna, or the increased frequency of forest fires and the desertification of vast expanses of arable land, or the spread of epidemics and the forced migration of large population groups.

Various studies tend to agree on the 60% incrimination of carbon dioxide for the creation of the greenhouse effect. A small concentration of CΟ2 in the atmosphere is the result of natural processes, but antrhropogenic activities, such as the combustion of oil products, of carbon and natural gas, or the forest fires, contribute to its substantial increase. Anthropogenic activities have added 2.3 trillion tons of CO2 to the atmosphere over the last 200 years. Overall, the concentration of CO2 in the atmosphere has increased by 31% since 1750. CO2 emissions today are about 12 times higher than in 1900, and its concentration in the atmosphere is the highest observed in the last 420,000 years. 

For further information concerning climate change, you may visit the relevant websites of the IPCC, www.ipcc.ch, the United Nations, www.un.org/climatechange and the European Union, http://ec.europa.eu/environment/climat/home_en.htm

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