Greenhouse gas effect refers to the process through which thermal radiation from the surface of the earth is absorbed and retained by the atmospheres’ greenhouse gases. The retained thermal radiation is then re-radiated in a distributive manner towards all directions. Some of the re-radiation are directed towards the lower layers of the atmosphere and the surface of the earth and consequently causes a higher temperature than the normallly expected temperature without the greenhouse gases.
The greenhouse effect occurs due to the following mechanism. The surface of the earth receives solar energy in the form of ultra violet (UV), near infra-red (IR) radiations and the visible light that pass through the atmosphere without any absorption taking place. The incoming radiation is then absorbed by the surface of the earth especially radiations within the wavelength of 0.2 to 4 μm that corresponds to the sun’s radiation temperature of 6000 K (Mitchell, John F. B., 1989). The heated surfaces then re-radiate the absorbed energy in much longer wavelengths than the incoming radiations. The longer wave lengths of the re-radiation from the surface are then absorbed by the greenhouse gases in the atmosphere. The energy is then retained and hence leads to a higher temperature than the other regions without greenhouse gases.
The main greenhouse gases include carbon dioxide that comprises of between 9 to 26 % of the total greenhouse gases. Methane gas that comprises of between 4 to 9 % of the total and Ozone gas, which is about 3 to 7 % of the total, also contribute to the greenhouse effect. Water vapour has also a greenhouse effect and contributes to the highest percentage of the total that range between 36 to 70 % of the total.
Carbon dioxide levels have been documented on a monthly basis by the Mauna Loa Observatory situated in Hawaii. Two independent scientific bodies; NOAA and the Scripps Institution of Oceanography measure the levels of the carbon dioxide monthly. According to the recent records, February, 2014 had 398.03 ppm (parts per million) (co2now.org). This data show a steady increase in the levels of CO2 since the observation began.
Carbon dioxide has been increasing due to several reasons. There has been a natural emission from volcanic eruptions that increase the naturally present CO2. The occurrence of natural fire such as wildfires also contributes to the increased carbon dioxide. Respiration and other aerobic activities also contribute to the natural increase. Anthropogenic activities like combustion of fossil fuels as coal, petroleum and natural gases that contribute to 13 to 40 % of the total CO2 (Page, S., Siegert, F., Rieley, J, Boehm, H., Jaya, A., and Limin, S., 2002) also contribute the highest percentage of all.
If the continued increase in the Carbon dioxide is not stopped, the world temperature shall increase as the trend has been. Global warming that is caused by increased carbon dioxide has serious environmental implications. The polar ice could melt and consequently lead to rise in ocean and sea levels. The high temperatures shall also alter the climatic conditions of the worlds’ leading to severe droughts and severe rains in other parts.
The current trend is clear enough of the future predicaments due to increased carbon dioxide and greenhouse effects. Therefore, it is certainly clear that an action has to be taken now to avert those predicaments earliest possible.
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