Introduction
The gaseous envelope which surrounds the earth is called atmosphere. The atmospheric envelope gets thinner or less dense with height and fades away completely about 800km above the ground, where atmosphere ends. But 99% of the atmosphere is concentrated in the lower 30 km.

One can survive without food for few weeks, without water for three days, but without air only for five minutes. It serves as heat regulator; balancing earth temperature from excessive heat by absorbing and scattering solar radiation. It maintains the temperature, so that neither excessive heat in the day hours or excessive cold in the night hours affect us. It works like an umbrella which protects the earth and its biotic elements from the harmful ultraviolet rays, x-rays, cosmic rays as well as the meteoroids. It helps in circulation of material and energy within the atmospheric envelope through its own motion. Aided by the atmosphere, sound can be heard, Sun and Moon can be viewed in luminosity and the stars can glitter in the sky at night. Due to its impact the sky is seen as blue, and we see the splendour of sunset.

Gases, water vapor and particulate matters are the main constituents of atmosphere. Nitrogen and oxygen constitute 99% volume of the atmosphere. Carbon dioxide is very important because of its ability to absorb heat. Ozone is another important gas, which can also absorb ultraviolet radiation. Nitrogen in air enters in to nitrogen cycle which maintains nitrogen content of the soil.

There are two approaches to divide the atmosphere. On the basis of chemical composition it is divided into two classes: homospheres- upto 80 km vertically and heterosphere – above 80 km. In other case on the basis of thermal profile it is divided into four: Troposphere- Up to 10 km, Stratosphere- 10-50 km, Mesosphere- 50- 80km, Thermosphere- above 80 km.

Weather and climate:Weather is the instantaneous state of the atmosphere, or the sequence of the states of the atmosphere as time passes. Weather can be defined as the condition of the atmosphere at any given time and place.

Climate may be defined as the average condition of the weather based upon statistics collected over a period of minimum thirty years. Climatology is the study of climate. Climate lies at the heart of physical geography. Climate influences vegetation, soils, landforms, and water resources, and many human activities as well.

Weather & climatic conditions are determined by six major elements:
Air temperature, air pressure, humidity of the air, amount and kind of cloud cover, amount and kind of precipitation, and speed and direction of the wind. Weather condition for any region or for the whole planet can be charted on a weather map containing information about all six of these factors.

The six elements determining weather conditions result from the interaction of four basic physical elements the Sun, the earth’s atmosphere, the earth itself, and Nature of landforms on the earth’s surface.

In this context to know about the atmosphere and weather & climate particular, exploring different aspects of weather elements, air pollution and its impact on global climatic scenario of global warming and climate change are very important .

Carbon and Climate Change: Carbon is an important component cycling in atmosphere, terrestrial and oceanic systems of the earth. Carbon dioxide released by the respiration of all living organisms is taken up by plants in the process of photosynthesis, in which the carbon is fixed as organic matter and the oxygen is released back into the atmosphere. When carbon in losses respiratory and non-respiratory processes are taken into account in terrestrial biosphere, including fires, harvests/removals, erosion and export of dissolved organic carbon by rivers to the oceans, the rest of the accumulated carbon goes for long-term (decadal) storage. Thus carbon moves in complex chemical and physical transfers from sources, or reservoirs, where carbon is released, to sinks, where carbon is taken up. Earth’s atmosphere, ocean, land, and living things can be both sources and sinks of carbon. In Earth’s atmosphere, CO₂ is only about 0.03% by volume, but it is an important “greenhouse” gas. It traps in the lower atmosphere much of the heat radiated from the Earth’s surface thereby maintaining the earth’s radiation budget. However concentrations of CO₂ have been constantly increasing due to CO₂ emissions from burning of fossil fuel, deforestation and large scale disturbance of land for urbanization.

Due to increasing CO₂ concentrations, the global average surface temperature (the average of near surface air temperature over land, and sea surface temperature) has increased since 19th century. Over the 20th century the increase has been 0.6 ± 0.2°C. India also witnessed a warming trend at a rate 0.6°C per century. In the state of Andhra Pradesh temperatures even rose to 48.9°C during May 2002, resulting in the highest one-week death toll on record. A number of environmental catastrophes have been consequently triggered as result of the climate variability. The initial impacts are tangible across the world including the decrease of artic ice caps and disappearance of several vulnerable species. Current research across the world is targeted over potential carbon sequestration mechanism to mitigate this climate change caused by CO₂ rise. Not only that in may cases it is link with local condition also like temperature inversion.