Assignment on Greenhouse Effect

A schematic representation of the exchanges of energy between outers space, the car this atmosphere and the earthy surface. The ability of the atmospheres to captures and recycle energy emitted by the Earth subspace is the defining characteristic of the green house effect.
Due to greenhouse effect Global warming is bearing a global warning for the low-lying sea-facing over populated country like Bangladesh. This perhaps has made the world community more concerned about than others environmental issue. But it is man who has made it so alarming through his unleilled one-sided development activities without taking the environmental aspects into account over time.


2. Greenhouse
Building designed for the protection of tender or out-of-season plants against excessive cold or heat. Usually a glass- or plastic-enclosed structure with a framing of aluminum, galvanized steel, or such woods as redwood, cedar, or cypress, it is used for the production of fruits, vegetables, flowers, and any other plants requiring special temperature conditions. It is heated partly by the sun and partly by artificial means. This controlled environment can be adapted to the needs of particular plants.

A greenhouse is a structure with a glass or plastic roof and frequently glass or plastic walls; it heats up because incoming solar radiation from the sun warms plants, soil, and other things inside the building. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall. These structures range in size from small sheds to very large buildings.

The glass used for a greenhouse works as a selective transmission medium for different spectral frequencies, and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. This warms the air near the ground, and this air is prevented from rising and flowing away. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature drops considerably. This principle is the basis of the autovent automatic cooling system. Greenhouses thus work by trapping electromagnetic radiation and preventing convection. Miniature greenhouses are known as a cold frame.

3. History
The idea of growing plants in environmentally controlled areas has existed since Roman times. Doctors for the Roman emperor Tiberius prescribed him a cucumber daily. The Roman gardeners used artificial methods (similar to the greenhouse system) of growing to have it available for his table every day of the year. Cucumbers were planted in wheeled carts which were put in the sun daily, then taken inside to keep them warm at night. The cucumbers were stored under frames or in cucumber houses glazed with either oiled cloth known as "specularia" or with sheets of mica. (Pliny the Elder and Columella).
The first modern greenhouses were built in Italy in the sixteenth century to house the exotic plants that explorers brought back from the tropics. They were originally called giurdini botanici (botanical gardens). The concept of greenhouses soon spread to the Netherlands and then England, along with the plants. Some of these early attempts required enormous amounts of work to close up at night or to winterize. There were serious problems with providing adequate and balanced heat in these early greenhouses.

4. Greenhouse Effect
The retention of part of the Sun's energy in the Earth's atmosphere in the form of heat as a result of the presence of greenhouse gases. Solar energy, mostly in the form of short-wavelength visible radiation, penetrates the atmosphere and is absorbed by the Earth's surface. The heated surface then radiates some of that energy into the atmosphere in the form of longer-wavelength infrared radiation. Although some of this radiation escapes into space, much of it is absorbed by greenhouse gases in the lower atmosphere, which in turn re-radiate a portion back to the Earth's surface. The atmosphere thus acts in a manner roughly analagous to the glass in a greenhouse, which allows sunlight to penetrate and warm the plants and soil but which traps most of the resulting heat energy inside. The greenhouse effect is essential to life on Earth; however, the intensification of its effect due to increased levels of greenhouse gases in the atmosphere is considered to be the main contributing factor to global warming.
The greenhouse effect is the process in which the emission of infrared radiation by the atmosphere warms a planet's surface. The name comes from an incorrect analogy with the warming of air inside a greenhouse compared to the air outside the greenhouse. The Earth's average surface temperature of 15 °C (288 K) is about 33 °C warmer than it would be without the greenhouse effect. The greenhouse effect was discovered by Joseph Fourier in 1824 and first investigated quantitatively by Svante Arrhenius in 1896. Global warming, a recent warming of the Earth, is believed to be the result of increased concentrations of greenhouse gases in the atmosphere. In addition to the Earth, Mars and especially Venus have greenhouse effects.

5. GHGs and Their Global Emissions
The concentrations of GHGs in the atmosphere are believed to have changed naturally on ice-age time scales, and have been increasing since pre-industrial times due to anthropogenic activities. Table-1 summarizes the present and pre-industrial abundances, current rates of change and the atmospheric lifetimes of GHGs. influenced by anthropogenic activities. The abundance of the GHGs was relatively constant for over a thousand years prior to the industrial revolution. However, with increasing population atmospheric GHG concentrations increased significantly. Evidences from air trapped in Antarctic and Greenland ice shows that there have been major increases in the concentrations of radioactively active gases since the beginning of the industrial revolution.

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