The Greenhouse Effect made simple
The Greenhouse Effect – a dictionary definition:
"The phenomenon whereby the earth's atmosphere traps solar radiation, caused by the presence in the atmosphere of gases such as carbon dioxide, water vapor, and methane that allow incoming sunlight to pass through but absorb heat radiated back from the earth's surface"
A step by step explanation of the greenhouse effect
Planet Earth luckily posses a blanket of gasses called atmosphere. The atmosphere is a mixture of different gases such as Nitrogen (78%) Oxygen (21%) Argon (less than 1%), other inert gases (Neon, Krypton), Carbon dioxide (0.04%), Methane (0.0018%), Water Vapors and traces of other gases (including Ozone).
The sun is a gargantuan hot object that acts like a gigantic Fusion Reactor and radiates its energy over a wide range of the spectrum (ultraviolet, visible light and infrared). Each gas behaves like a filter – it can absorb certain wavelengths, it can scatter other wavelength. The Ozone absorbs efficiently ultraviolet wavelengths, ultraviolet is not good and present a life hazard to living organisms. The radiation in the visible wavelengths is scattered by the atmosphere and partly finds its way to Earth surface. Earth surface (land, buildings, roads, etc.) warms up and radiates back to the atmosphere in longer wavelength known as infrared. The longer wavelength radiation is absorbed by the Carbon Dioxide, the Methane and other greenhouse effect gasses (Earth and its atmosphere behave like a global scale greenhouse). The end result is what is now called Global Warming
The greenhouse effect, is it good or bad?
For eons there was a delicate balance between how much radiation energy went through the atmosphere and how much energy was reflected back to deep space. The Carbon Dioxide was "just right" to keep this delicate equilibrium in place. Animals inhale Oxygen and exhale carbon dioxide while plant "inhale" carbon dioxide and "exhale" oxygen so the carbon dioxide concentration was right. Planet Earth was inhabitable, predators hunted grass eaters, grass eaters fed on grass and the ecological system was dynamically balanced. At that time the green house effect was "just right" and was beneficial to life.
With the increasing industrialization and with the increasing burning of fossils, more and more carbon dioxide is released to the atmosphere and more and more heat is absorbed in the atmosphere (and not free to go to deep space). Adding to that our appetite to beef increased. The impact is double: rain forests are burned down to make room for grazing fields (less trees to inhale carbon dioxide) and more cows (and sheep) are releasing more methane to the atmosphere.
Al Gore in his film "An Inconvenient Truth" depicted a chilling view of what might happen if this trend continues. Global Warming is a fact that might get into a thermal runaway (Earth will be like Venus – inhabitable). Governments are starting to have carbon dioxide under control through legislation, taxation and education. Although the Copenhagen convention did not fulfilled all our hopes, it was a small step in the right direction.
It is up to each one of us to reduce his family carbon dioxide footprint, to save energy
and to use renewable energy (solar and wind)
The Benefits of the Greenhouse Effect
For millenniums people were using Green Houses to get crops not in the season, earlier than usual or in a bigger quantity per acre. Plastic sheets or glass are used as a material transparent to light and opaque to heat (at infrared wavelengths)
A modern use is for solar hot water heaters. Solar hot water collectors use the effect to heat up water for domestic use. In this application the benefit of greenhouse effect to the household economy is tremendous, It can save 20-30% on the domestic energy bills. By the way, solar electric panels (solar panels) that generate electricity and look very much like the solar thermal collectors has nothing to do with the green house effect. They utilize the photovoltaic effect to convert sun radiation to DC (Direct Current) electricity.
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