The Greenhouse Effect
The Greenhouse effect is the trapping of the sun's warmth in the lower atmosphere of the earth caused by certain gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane) that trap energy from the sun. The term "greenhouse effect" may be used to refer either to the natural greenhouse effect, due to naturally occurring greenhouse gases, which enable the energy necessary for sustaining life on earth, or to the enhanced greenhouse effect, which results from gases emitted by human activity which results in global warming that threatens life on earth.
The greenhouse effect is caused by greenhouse gasses; the most important greenhouse gasses in Earth's atmosphere are: water vapor, carbon dioxide, and methane.
Recently, the greenhouse effect has gotten stronger. Scientists believe this is because humans have been using large amounts of fossil fuels, which release carbon dioxide when they are burned. Since carbon dioxide is a greenhouse gas, it has caused the planet to warm over the past 150 years.
The greenhouse effect was first discovered by Joseph Fourier in 1824. Mars, Venus and other planets with atmospheres also have greenhouse effects.
For more information (background, pictures, experiments and references): Greenhouse Effect
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