The Greenhouse Effect

The Greenhouse Effect has existed as long as the Earth has had atmosphere. The sun radiates energy as ultra-violet or short wave radiation. This energy travels easily through the atmosphere just as light passes through the glass in a greenhouse. When it reaches the Earth's surface some of the energy is reflected back as infra-red or long wave radiation. This energy is not transmitted as easily as short wave radiation and the atmosphere traps some of the energy.

It is the Greenhouse Effect that ensured that conditions were right for human life. Without it, the world's average temperature would be about -18°C, the same temperature as winter in Moscow. The real problem lies with Global Warming. Gases are being released by human activities faster than plants and the sea can absorb these. The more gases that are released the higher the temperature. 

Carbon Dioxide
Carbon Dioxide accounts for 55-60% of the warming effect and 85% of the human production of Carbon Dioxide is the result of fossil fuel burning. About 15% is due to the burning of forests, mainly in places like the Amazon. Although the amount of Carbon Dioxide in the atmosphere is quite small, about 350 parts per million parts of air, it has serious climatic effects. Since 1860 the temperature has risen by about 1°C and could rise by 2°C by 2030. And the amount of Carbon Dioxide in the atmosphere is increasing.

Table 1

Other Greenhouse Gases
Until recently, chlorofluorocarbons (CFC's) accounted for about 25% of the warming effect. In addition they are responsible for the destruction of the Ozone Layer. It is hoped that CFC's will soon be completely phased out.

Methane accounts for 15% of Global Warming. The main sources of this gas are the burning of forests, the flatulence of livestock, coal mining and decomposing rubbish. The fact that Ireland has large herds of cattle will make it difficult to reduce the amount of methane it produces. However, if the amount of grass and silage that is fed to the animals is reduced, so will the production of methane. The problem is that this will cause the price of food to rise.

The Possible Effects of Global Warming
No one is entirely certain what the result of Global Warming will be. Some scientists believe that Ireland will be about 1°C warmer. This would mean that Ireland could also be wetter because warmer air can hold more moisture. The change in temperature would benefit farmers because every 1°C increase in average temperature increases the growing season by about two weeks. Crops like wheat and corn could be grown in more areas.

But it is not all good news. As the sea level rises due to melting ice coastal areas could be flooded and coastal erosion could increase. Increased rainfall could cause flooding along many rivers. As most of Ireland's people live along the coast or beside rivers this could be a serious problem in the future. Other problems are shown in Table 2.

Table 2

Questions

1. If the sea level rises 1 metre for every 0.5°C, how far has it risen since 1860? How much will it rise by the year 2030?
2. Using the physical map of the world in your atlas or wall chart, describe how a temperature rise of 3°C would affect the following areas;
   (a) Ireland (b) Western Europe (c) The Pacific Islands (d) Africa 
3. Study Table 2. Divide the possible effects in those that are good and those that are bad. Decide whether the benefits of Global Warming are greater than the problems. You should then decide whether we should continue to use fossil fuels based on your decision.
4. If you decide that we should stop using Fossil Fuels what should we use instead?
5. If the amount of Greenhouse Gases continues to rise, Global arming will become worse. Working in pairs, decide how the mount of these gases can be reduced
6. One way that each of us can help to reduce the production of Greenhouse Gases is to conserve energy. Try to make a list of the different ways that you can conserve energy in your home and at school.