Greenhouse Effect and Global Warming

Greenhouse Effect and Global Warming

Greenhouse effect
 As the sun’s rays enter our atmosphere, the Earth’s surface absorbs light energy from the sun and emits it as heat energy.
 About 31 % of the incoming radiation from the sun is reflected directly back to space by the earth's atmosphere.
 Another 20 % is absorbed by the atmosphere. The rest of the incoming radiation is absorbed by the earth's oceans and land, where it is converted into heat, warming the surface of the earth and the air above it.
 However, several gases in Earth’s atmosphere — such as carbon dioxide, methane and water vapor work like a blanket over the earth’s surface to retain much of this heat from escaping to outer space. That helps to warm our earth’s atmosphere. The gases do this by absorbing the heat and radiating it back to Earth’s surface. Such gases are called “greenhouse gases” because of their heat-trapping effect.
 The phenomenon wherein the earth’s atmosphere trap the heat from the sun and retain it from escaping into outer space and increasing the earth’s surface temperature is called “Greenhouse effect”. Without this greenhouse effect, Earth would be too cold to support most forms of life.

Global Warming
 Global Warming is the increase of Earth's average surface temperature due to effect of greenhouse gases, such as carbon dioxide, methane , nitrous oxide and water vapor which trap radiated heat that would otherwise escape from Earth into the outer space.

Concept of Greenhouse

You might have seen in botanical garden plant growers growing plant in green houses.
Lets us try to understand the concept of growing plants in green houses.

 The most basic greenhouse would be a simple transparent structure, preferably made up of glass or transparent plastic.
 When the radiations of sunlight enter through the transparent walls of the greenhouse, it heats up the floor of the greenhouse.
 The floor releases some of this thermal energy, which heats the layer of air at the bottom of the greenhouse.
 Warmer air is lighter than cooler air, so the heated air rises to the top of the greenhouse. When the heated air rises, cooler air replaces it at the bottom of the greenhouse. This air becomes heated by the floor and also begins to rise.
 This circulation of air helps keep greenhouse warmer than outside atmosphere.
 Hence, greenhouses are useful for growing plants in cold climatic condition.

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