Image from EPA Global Warming Climate Website
The ‘greenhouse effect’ is a naturally occurring phenomenon within the atmosphere of a planet. On Earth, incoming radiation from the Sun strikes the atmosphere, where most is reflected and the remainder is allowed to pass through. The radiation, mostly visible light, is absorbed by the Earth’s surface, which in turn is warmed. The surface then reradiates this energy at a longer wavelength, which corresponds to infrared radiation. Some of the infrared radiation escapes into space while some is absorbed by greenhouse gases, which reemits the energy in all directions. This process warms the surface and the atmosphere of the Earth. Without this natural process, the Earth would be too cold to sustain most forms of life. It is estimated that without the small amount of carbon dioxide that is present in the atmosphere (0.03%), the average temperature of the Earth would be 60° F colder. Thus, the greenhouse effect acts like a blanket keeping our planet at a livable temperature.
The greenhouse effect can be ‘enhanced’ by the addition of carbon dioxide to the Earth’s atmosphere through human activity. Carbon dioxide is not the only greenhouse gas. Naturally occurring water vapor also plays a significant role in warming our atmosphere. Other greenhouse gases include methane, nitrous oxide, HFCs, PFCs, SF6, and a group known as criteria pollutants.
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