Introduction: The "greenhouse effect" is widely discussed in the media, and although its details are complicated, its principles are not difficult to understand. Without a greenhouse effect, radiation from the Sun (mostly in the form of visible light) would travel to Earth and be changed into heat, only to be lost to space. This scenario can be sketched as follows:
Sun’s radiation → absorbed by Earth → Re-radiated to space as heat
The greenhouse effect is a process where energy from the sun readily penetrates into the lower atmosphere and onto the surface of Earth and is converted to heat, but then cannot freely leave the planet. This can be sketched as follows:
Sun’s Radiation → absorbed by Earth → some re-radiated to space as heat → some trapped by the atmosphere
Due to the presence of certain “greenhouse gases” that trap heat, like carbon dioxide, methane, water vapour, and CFC’s, the atmosphere retains the sun’s radiation and warms up the planet. By increasing the abundance of these gases in the atmosphere, humankind is increasing the overall warming of the Earth’s surface and lower atmosphere, a process called "global warming." The figure below illustrates the radiation balance and the role of greenhouse effect.
The Radiation Balance: Another way to think about the greenhouse effect is to consider that according to physics the radiation we receive from the Sun must be equally balanced by the heat Earth radiates out to space. If we were to give back less energy than we receive, our planet would soon be too hot for life. Likewise, if we were to give back more energy that we receive, our planet would soon be too cold for life. This can be written as a balanced equation of radiation: Solar radiation input to Earth = Earth’s output of re-radiated heat
If we were to measure the temperature of the Earth from space, the Earth 's "surface" would show a temperature appropriate for this requirement of energy balance: a measurement of
References: http://earthguide.ucsd.edu/virtualmuseum/climatechange1/02_1.shtml http://www.wmconnolley.org.uk/sci/wood_rw.1909.html http://www.columbia.edu/~vjd1/greenhouse.htm http://www.lenntech.com/greenhouse-effect/greenhouse-effect-mechanism.htm http://www.met.ie/education/pdfs_eng/Lesson%20Plan%20Greenhouse%20Effect.pdf http://www.google.co.in/search?hl=en&q=green+house+effect&bav=on.2,or.r_gc.r_pw.r_qf.&biw=1366&bih=667&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=JdlvUK6BJserrAel8oHICw