The Earth gets its heating energy from the rays of the sun. These rays are filtered down to the surface of the Earth through the layer of gases (atmosphere), which surrounds the Earth. While most of the rays reach the Earth's surface, some are reflected back out of the atmosphere. The heat of the sun's rays is then absorbed by the Earth's surface and that too is radiated back into the layer of atmospheric gases.
When this happens, some of the heat is absorbed by the atmospheric gases and is not allowed to escape back into space. This process is known as the 'Greenhouse Effect'.
There are some specific gases in the atmospheric layer, which trap the heat emitted back from the surface of the Earth. These gases are known as 'Greenhouse Gases'. Specifically, they are water vapor, carbon dioxide, ozone, methane, nitrous oxide, and chlorofluorocarbons. Thus, if the amount of these gases increases in the atmospheric layer, it is normal to expect that more and more of the heat emitted by the surface of the Earth, will get trapped within this atmospheric layer and will not escape back into space.
As this keeps on happening, the Earth will become warmer and warmer. This process is also commonly known as the process of 'Global Warming'.
The process described above is held to be quite similar to what happens in a greenhouse, which is a house made out of glass, and is used to grow plants in the winter season. What happens here is that the rays of the sun come in through the glass, and then the heat remains trapped within the glass walls and is not allowed to escape. In this manner, the inside remains warm, and allows the plants to grow during the winter season as well.
However, this analogy has come under some criticism, because it does not allow for the fact that the heat is not allowed to escape at all from the greenhouse. Whereas, the Earth's atmospheric layer does allow for the heat to actually escape. The greenhouse is a closed system, whereas the Earth is not a closed system.
The Role of Man in the Greenhouse Effect
Human beings are also responsible for what is happening to the Earth. The production of greenhouse gases is largely due to the burning of fossil fuels such as petroleum, coal, and natural gas. As mentioned before, the increasing heat which remains trapped within the atmospheric layer will end up creating warmer climates across the globe. This process will cause significant climatic changes all over the Earth. This can result in many problems in the long run.
Many movies and books are a focus of these proposed scenarios, which feature the long term effects of global warming.
To combat this rising threat of global warming, countries all over the world are trying to create pollution free environment and planting trees. Re-forestation is a very natural method of creating an environment where global warming can be controlled, as plants and trees actually absorb carbon dioxide and release oxygen into the atmosphere. Automobile companies are focusing on building 'Green' cars, which release reduced amounts of pollutants into the atmosphere.