What is Greenhouse effect? Greenhouses are those glass buildings put up to nourish plants and get fruits even in the cold unfavorable seasons. These glass walled structures let the sunlight come inside but do not let the heat from inside go out. They trap heat and this makes the interior of the green houses warmer than the outside. This artificial warmer environment makes plants to go normally and bear fruits.
The Greenhouse phenomenon experienced by a planet such as earth is different from the above mentioned greenhouses. But there is a commonality. This is that the greenhouse effect keeps the earth warmer than the temperature the planet should be having if this phenomenon is not there. This commonality of creating warmer atmosphere is what made the scientists coin the name greenhouse effect. Other than this the greenhouse phenomenon experienced by earth and greenhouses has no relations.
Earth receives the energy from the sun. This energy comes in the form of sunlight which falls in the visible or near-visible (e.g., ultraviolet) part of the spectrum. All the solar radiations that reach the earth’s atmosphere do not touch the earth surface. In fact about one third of the radiations are reflected back into the space by the top of the outer atmosphere. Two third of the radiations penetrate the outer atmosphere. They get absorbed largely by the land and ocean surface and to a lesser extent by the atmosphere.
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Earth is a very cold place. It uses the incoming energy in variety of ways to make life possible. But it also has to maintain a balance and in doing so it reflects back rest of the energy. This reflected energy falls in the lower wavelength infrared part of the spectrum and it actually is thermal radiation. In its upward journey the thermal radiations come in contact of the atmosphere, including clouds. They absorb it and reradiate in all the directions. A part of it comes back towards Earth. This warms the surface of the earth and is known as greenhouse effect.
Is Greenhouse effect bad for us?
Had this natural greenhouse effect not been there, the average temperature at Earth’s surface would be -18oC which is much less than the actual (for example) average surface temperature of 20th century (14oC). This means that the greenhouse effect is responsible in pulling up the average surface temperature from a point much below the freezing point of water.
What is the issue if greenhouse effect is beneficial for the earth ? In the industrialized world the greenhouse effect of the earth’s environment is continuously increasing which means that the earth is getting warmer year by year. The reason behind this worming is the presence of greenhouse gases in excess. These gases are produced during a variety of human activities such as in the burning of fossil fuels and from the industries and get accumulated in the atmosphere. These are responsible for intensifying the natural greenhouse effect and causing global warming.
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Contributors to Greenhouse effect?
Nitrogen and oxygen are the two most abundant gases. But these do not exert greenhouse effect. Instead water vapours, carbon di oxide, methane, nitrous oxide, ozone and many other gases present in the atmosphere in small amount contribute towards greenhouse effect in a big way.
In the industrial era, on one hand the burning of fossil fuels has released tremendous amount of CO2 in the atmosphere. On the other hand the most abundant sink of carbon di oxide present on the land surface i.e. forests have degraded. This has resulted in the building up of its high concentration in the atmosphere.
The more the concentration of CO2 in the atmosphere, the more warming we will face. This in turn will result in the increase in the concentration of water vapours in the atmosphere. But as the global warming potential of water vapours is even more, there will be more warming. This will further enhance the water vapour concentration in the atmosphere. It is thus a self-reinforcing cycle. According to IPCC this water vapour feedback can double the increase in the greenhouse effect caused by the additional CO2.
Clouds are also able to absorb the infrared heat radiations. They contribute towards greenhouse effect and exhibit the feedback mechanism. However, they are also good in reflecting away the solar radiations and thus exert cooling effect as well. The research related to interrelation between climate warming, its effects on changes in clouds and the feedback mechanism is in progress.