Four-billion years ago, this earth was covered by large amount of hydrogen and oxygen which became water and united as glacier. At that time, the earth’s temperature was -180˚ and unable all living creatures lived on the earth. However, every single day, the energy received from the sun affects the increase of the earth’s temperature, thus the heat is returned back to the atmosphere as infra-red waves and some of the energy is absorbed by 'greenhouse gases'. This process enables the average temperature of the earth increases into ±15 ˚ and, consequently, also enables the earth to be habitable.
The greenhouse effect is best explain by referring to circumstances where the short wavelengths of visible light from the sun pass through a transparent medium and are absorbed, yet the longer wavelengths of the infrared re-radiation from the heated objects are unable to pass through that medium. The trapping of the long wavelength radiation leads to more heating and a higher resultant temperature. Moreover, the greenhouse effect has also been widely used to describe the trapping of excess heat by the rising concentration of carbon dioxide in the atmosphere. The carbon dioxide strongly absorbs infrared and does not allow as much of it to escape into space. It means, in essence, actually greenhouse effect is really useful for the earth to be habitable.
However, there is not only one gas, carbon dioxide, which trapped by greenhouse effect, but also other gases. Briefly, there are two kinds of gases cause greenhouse: controlled and uncontrolled as shown by the following table:
*Not all greenhouse gases are to be controlled under the Kyoto Protocol (see IPCC list of greenhouse gases for further understanding of greenhouse gases).
**The three major greenhouse gases
(http://www.climatechangesask.ca/html/learn_more/Emissions/GHGs/index.cfm)
The greenhouse effect is best explain by referring to circumstances where the short wavelengths of visible light from the sun pass through a transparent medium and are absorbed, yet the longer wavelengths of the infrared re-radiation from the heated objects are unable to pass through that medium. The trapping of the long wavelength radiation leads to more heating and a higher resultant temperature. Moreover, the greenhouse effect has also been widely used to describe the trapping of excess heat by the rising concentration of carbon dioxide in the atmosphere. The carbon dioxide strongly absorbs infrared and does not allow as much of it to escape into space. It means, in essence, actually greenhouse effect is really useful for the earth to be habitable.
However, there is not only one gas, carbon dioxide, which trapped by greenhouse effect, but also other gases. Briefly, there are two kinds of gases cause greenhouse: controlled and uncontrolled as shown by the following table:
*Not all greenhouse gases are to be controlled under the Kyoto Protocol (see IPCC list of greenhouse gases for further understanding of greenhouse gases).**The three major greenhouse gases
(http://www.climatechangesask.ca/html/learn_more/Emissions/GHGs/index.cfm)
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