Inside a greenhouse, the sun’s radiation comes through the glass and heats up the air inside. This heat remains within the greenhouse; therefore the inside of the greenhouse remains warm and humid, maintaining conducive conditions for the plant growth.

The same thing happens on Earth, Greenhouse effect refers to the natural heating up of the surface temperature of the Earth. This heating up process is caused by the greenhouse gases, like moisture, carbon dioxide, methane and nitrous oxide, which are naturally present in our atmosphere. The problem of greenhouse effect is compounded by the fact that man-made air pollution emits a huge proportion of these greenhouse gases. These gases gave a warming effect which is similar to that of a plant greenhouse. They do not allow radiated heat to be released out to space. The more greenhouse gases there are in the atmosphere, the warmer it will get.

[Animated guide to Global Warming]

Greenhouse Gases

Greenhouse gases are the ones that cause radiated heat to be trapped in the Troposphere, as these gases reflect the heat back towards the earth and prevent its radiation out of the atmosphere, resulting in a rise in the temperature of the Earth surface. These gases are naturally present in the atmosphere; therefore a natural warming of the Earth takes place. However, the more greenhouse gases there are in the atmosphere, the warmer the temperature will get - a situation we have to avoid. The three main greenhouse gases, Carbon dioxide, methane and nitrous oxide are discussed here.

• Carbon dioxide

Carbon dioxide exists in abundance on the Earth’s atmosphere. It is mainly released by the burning of fossil fuels. It is also given out during aerobic respiration by living things, such as humans. On the other hand, Carbon dioxide is taken in by plants during photosynthesis, therefore, planting of more trees can help to reduce the carbon dioxide concentration.

• Methane

Methane is naturally present in the atmosphere due to bacterial decay of vegetation, decomposition of animal waste, from cattle, and enteric fermentation in animals. However the amount of methane is increasing due to human activities such as agricultural processes (e.g. wet-land rice cultivation), production and distribution of natural gases and petroleum, coal mining and incomplete fossil fuel combustion.

• Nitrous oxide

Nitrous oxide is naturally produced by lightning and forest fires. However, it is also produced by motor car engines and power stations. Agricultural and industrial activities with combustion of solid waste and fossil fuels also attribute to the increase in nitrous oxide levels.

[ What is Global warming?]