THE GREENHOUSE EFFECT AND GLOBAL WARMING
The moon is very cold because it is a long way from the sun; and, yet, the earth, which is the same distance, is warm. This is largely because of the carbon dioxide in the earth's atmosphere. Heat from the sun passes through the carbon dioxide to the surface of the earth, but when the earth radiates this heat back out into the atmosphere, it is absorbed by the carbon dioxide which then re-radiates in all directions: some goes out into space but some goes back to the earth. As a result the earth is 30-40°C warmer than it would be if there was no carbon dioxide in the atmosphere.
This process is called the Greenhouse Effect because it works just like a greenhouse in cold climates. The glass panes of the greenhouse allow the short waves of the sun's heat to pass into the building, but the long-wave heat radiating from the warmed surfaces inside cannot pass out again. Thus the inside of the building becomes a lot warmer than the outside, so that plants can be grown in cold weather.
It follows therefore that if the carbon dioxide in the atmosphere is increasing, more heat will be trapped inside the Biosphere and the earth's average temperatures will increase. As a result of burning coal and oil, the amount of carbon dioxide in the atmosphere is increasing; and, global temperatures have increased by about 0.45°C since 1900; and, mostly since 1940. This may seem insignificant, but it is enough to have caused the shrinking of Alpine and Polar ice caps causing a sea level rise of about 1.5mm per year over the same period. These processes are complex and not fully understood, but they appear to be accelerating.
Carbon dioxide is not the only Greenhouse gas. It makes up about 55% of the total. Pollutants from air-conditioners and refrigerators (Chloroflurocarbons - CFCs) make up about 20%; and, Methane makes up 15%. Gas flaring in the Niger Delta is considered to be a major source of Greenhouse gases.
| FROM THE SWISS AGENCY FOR THE ENVIRONMENT FORESTS AND LANDSCAPE – SEPTEMBER 1997: The (2) most important greenhouse gases resulting from man’s activities: Carbon dioxide (CO₂) | |
| Natural concentration in the atmosphere | 280 ppm |
| Increase in concentration since the beginning of industrialisation | 30% |
| Lifetime in the atmosphere | 50-200 years |
| Global Warming Potential | 1 (i.e. CO₂) |
| Contribution to increasing natural greenhouse effect | 75% |
| Main cause (globally) for its increase in concentration | Fossil fuels |
| Main source of its emissions in Switzerland | Fossil fuels (91%) |
