A greenhouse is a glass structure that traps solar energy and heats the interior, while the roof and walls slow down the escape of heat. This allows us to grow plants when sunlight is low. This process resembles how the atmosphere keeps the earth warm by trapping solar heat and hence the term ’greenhouse effect’ is used to describe the earth’s heating process. Without the greenhouse effect, the average temperature of the earth’s surface would have been minus 18 degree Celsius rather than the present average temperature of 15 degree Celsius.
When solar radiation enters the atmosphere, it is absorbed by the clouds and gases and heats the earth’s surface. The earth, in return, reflects some of this heat into the atmosphere as infrared radiation. Most of this infrared radiation gets absorbed by atmospheric gases such as carbon dioxide, methane, nitrous oxide and ozone, commonly known as greenhouse gases. These gases send the infrared radiation back to the earth’s surface, thereby heating the surface again. This cycle repeats several times, thereby resulting in the greenhouse effect.
In the last few decades, the amount of greenhouse gases, particularly carbon dioxide, has increased in the atmosphere, primarily due to the burning of fossil fuels. This has resulted in continuous heating of the earth, which has led to global warming. In the last three decades, the temperature of the earth has increased by 0.6 degrees Celsius. This rise in temperature resulted in odd climatic changes such as the El Nino effect and melting of polar and mountain ice caps. This also raised the sea level, thereby increasing the chances of submersion of many coastal areas.
Global warming can be controlled by reducing the use of fossil fuels, reducing deforestation, optimally utilising energy and planting trees. International organisations such as the United Nations Environment Programme and Greenpeace are taking measures to control global warming and greenhouse effect.