Green House Effect.
Greenhouse Effect plays a huge role in helping warm the earth’s atmosphere. The atmosphere is transparent to incoming ultra violet rays, which is absorbed by the earth’s surface.
The sun warms the earth surface. As heat energy from the sun passes through the atmosphere, almost three quarters of the energy gets absorbed into the earth. Some part of this energy is reflected back into the atmosphere from the land and ocean surface. This reflected heat energy will be reflected back into space. The rest actually remains behind to heat the earth. In order to establish a balance, the earth must radiate some energy back into the atmosphere. As the earth is much cooler than the sun, it does not emit energy as visible light. It emits through infrared or thermal radiation. However, certain gases in the atmosphere form a sort of blanket around the earth and absorb some of this energy emitted back into the atmosphere. Without this blanket effect, the earth would be around 30 o C colder than it normally is. These gases like carbon dioxide, methane, and nitrous oxide, along with water vapour, comprise less than one per cent of the atmosphere. They are called ‘greenhouse gases’ as the working principle is same as that which occurs in a greenhouse. Just as the glass of the greenhouse prevents the radiation of excess energy, this ‘gas blanket’ absorbs some of the energy emitted by the earth and keeps temperature levels intact. This effect was first recognized by a French scientist, Jean-Baptiste Fourier, who pointed out the similarly in what happens in the atmosphere and in a greenhouse. Hence he terms the “greenhouse effect.”
