Tag: pollution and its effects

The greenhouse effect is a naturally occurring phenomenon responsible for heating surface and atmosphere of earth. It is caused due to the presence of greenhouse gases like CO$ _2$, CH$ _4$ and CFCs etc. An excess amount of these gases cause global warming. The greenhouse gases are responsible for the greenhouse effect.

The burning of fossil fuels leads to increase in the concentration of carbon dioxide levels in the atmosphere. Svante Arrhenius (1859-1927) was a Swedish scientist who was the first to claim in 1896 that fossil fuel combustion may eventually result in enhanced global warming. He proposed a relation between atmospheric carbon dioxide concentrations and temperature. He found that the average surface temperature of the earth is about $15^0$C because of the infrared absorption capacity of water vapour and carbon dioxide. This is called as the natural greenhouse effect. 

The best solution to combat greenhouse effect is to plant trees. Trees absorb carbon dioxide and give off oxygen. A single tree will absorb approximately one ton of carbon dioxide during its lifetime.

Greenhouse gases are the gases which contribute to global warming. When the concentration of these gases increases in the atmosphere they form a layer which traps the solar radiation. Due to the trapped long wave infrared radiation, the temperature of the earth increases which leads to global warming. So the correct answer is option C.

The total carbon dioxide content in the atmosphere is 0.03%. The percentage of carbon dioxide is balanced by respiration and photosynthesis. Solar radiation falls on earth's surface heating it, while a small proportion is reflected back, and earths surface re-emits heat in the form of infrared radiation but part of this does not escape into space as atmospheric gases (e.g., carbon dioxide, methane, etc.) absorb a major fraction of it. These gases like carbon dioxide and methane are commonly known as greenhouse gases because they are responsible for the greenhouse effect. Increase in the level of greenhouse gases has led to considerable heating of earth leading to global warming. Thus, the correct answer is option A..

Without the Greenhouse gases, the average temperature of earth would be 0$^{o}$ F or -20$^{o}$ C. The naturally present Greenhouse gases allow most of the incoming solar radiations to warm the earth surface and do not let the thermal radiations to escape into the space. However, anthropogenic contribution to the Greenhouse gases increase the level of solar radiations trapped and thus increase the overall temperature leading to global warming.