Greenhouse Effects, Global Warming, Ozone Layer Depletion

Greenhouse effects

The greenhouse effects are defined as the warming effect near the earth surface due to the various gases. Without this effects, the average temperature of the earth would be 33-degree centigrade lower than that of the today.

The greenhouse gases acts like the glass or the plastic roofs and the walls of the atmosphere. The sunlight enters in a greenhouse through the glass and they heat the interior. The roof and the walls show the scope of the heat. This increasing temperature is due to the accumulation of the heat trapped gases like carbon dioxide, methane, chlorofluorocarbon, nitrogen dioxide. When the concentration of these gases increases, they enhance the greenhouse effect by the trapping of the immediate solar radiation from the earth. There are many major gases which play the vital role for the greenhouse effects are as follows:

1: CO₂

2: CH₄

3: NO₂

4: CFCs

Anthropogenic gases for the climate change

1: CO₂

Mainly the industrial revolution combusting of the fossil fuels and the deforestation have led to the 26% in the CO₂ in the atmosphere. The estimated level of the CO₂ during the period of the 1000-1800 A.D. was about 270-290 ppm and the present level is found to be 353ppm. Other activities than the combustion of the fossil fuels and the deforestation, human activities are putting 5.5 GT of the carbon into the atmosphere annually which helps to the increase of the greenhouse effect.

2: CH₄

The second greatest influence on the temperature is due to the CH_4. The major source of the atmospheric methane is rice field, biomass building, animals and the wetlands. Methane is more effective insulator level over 20 times more heat than does the same amount of the carbon dioxide. Methane is immediate during the foam production and the transport of the coal natural gases and oil.

3: NO₂

Nitrous oxide is the important atmosphere gas. The increase in the concentration of the nitrous oxide in the atmosphere has evolved considerable interest of its role in destroying the ozone layer. Globally NO₂ concentration is increasing at the rate of the 0.2-0.3 % year. The most important man-made the source of the NO₂ are biomass burning and fossil fuels combustion. Nitrous oxide is powerful insulating gas released primarily by burning of the fossil fuels. NO₂ traps about 300 times more heat than does the same amount of CO_2.

4: CFCs

There is no natural source of the CFCs but they exist in the atmosphere from the foam production refrigerators and from other AC devices having a long lifetime. These compounds are known to be up to 10000 times more efficient at the absorbing the infrared radiation. It is estimated that every year 362000 metric tonnes of CFCs are released into the atmosphere with lifetimes 70-100 years. This compound is primarily responsible for the destroying of the ozone layer.

Global warming

The energy that lights and warm the earth which comes from the sun. Most of the energy that comes into our planet is short wave radiation in which visible light also fall there. When this energy strikes the earth surface, the energy in the turn releases some amount of this heat as long radiation i.e infrared radiation. Much of this long wave radiation i.e infrared radiation makes it all the way back out to space but a portion of this is trapped in the earth atmosphere. Certain gases in the atmosphere including the water vapour carbon dioxide and the methane provide the trap. Absorbing and the reflecting waves radiated by the earth. These gases conserve the heat as the glass in a greenhouse gases are known as water vapour, carbon dioxide, methane and the nitrous oxide. As the concentration of these greenhouse gases in the atmosphere increases more heat energy remains trapped below.

The consequences of the global warming are very serious that threat to the existing ecosystem. It is expected to melt the polar ice caps and glaciers as well as the warm oceans which will expand its volume had raise sea level by an estimated 9 to 10 cm, flooding some region and even entire island. Some regions in the warmer climates will receive more rainfall than before it used to happen. But the soil will dry out faster between storms. This soil dryness may damage food crops disrupting foods supplies in the some part food supplies in some part of the world hence the global warming has an adverse effect on whether agriculture, plants and animals like human health, on the other hand, some scientist believe that global warming has food effect of glacier and the dry land because of cooling of the temperature.

Ozone layer depletion

In this region of the atmosphere from 19 to 48 km above the earth surface, the concentration of the ozone is high and up to the 10ppm so this region is termed as the ozone layer. The ozone forms in that layer by the action of sunlight on the oxygen. This action has been taking place for many millions of years but naturally occurring nitrogen compounds in the atmosphere apparently have kept the ozone layer concentration at a fairly stable level. The high concentration of the ozone at the ground level are dangerous to breathe and can damage the lungs. However, the ozone layer of the atmosphere protects the life on the earth from the full force of the sun's cancer-causing ultraviolet rays. So the ozone of the atmosphere is critically important.

In the late 1970s, scientist discovered that the ozone layer was being attacked by the chlorofluorocarbons (CFCs). It is the chemical used in the refrigerator, air conditioning systems cleaning solvents and the aerosols sprays. CFCs release the chlorine into the atmosphere which in turn break the ozone down into its constituents parts of the oxygen. Because chlorine is not affected by the interaction of the ozone each chlorine molecule has the ability to destroy a large amount of the ozone for an extended period of time.

The ozone hole is the term used to denote the thinned region of the ozone layer. It is predicted to cause an increasing amount of the harmful UV radiation on the earth surface. UV radiation cause skin cancer and attacked the human beings damaged the crops and also cause damage to the plankton. Beginning in the early 1980s, a research scientist working in the Antarctica have detected a periodic loss of the ozone in the atmosphere high above the continent.

Because of the presence of the chlorine molecules in the ozone layer, the number of the ozone molecules is decreasing. The decrease in the number of the ozone molecules shows the seasonal variation. The depletion is more during the months of the August to October. The deficient ozone molecules are formed in the other seasons. So these seasons do not experience the ozone hole phenomena. However, a continual decrease has been observed in the ozone layer.

References:

.S.C., Santee. Environmental Science. India, New Center: New Center Book Agency (P) Ltd, 2004.

Lal, D.S. Climatology, Sharda Pustak Bhawan, Allahabad.(2010)