The atmosphere is a mixture of many gases. In addition, it contains huge numbers of solid and liquid particles, collectively called "Aerosols". Some of the gases may be regarded as permanent atmospheric components which remain in fixed proportion to the total gas volume. Other constituents vary in quantity from place to place and from time to time. If the suspended particles, water vapour and other variable gases were excluded from the atmosphere, then the dry air is very stable all over the earth up to an altitude of about 80 kilometres. Nitrogen and oxygen make up nearly 99% of the clean, dry air. The remaining gases are mostly inert and constitute about 1% of the atmosphere. Besides these gases, large quantities of water vapour and dust particles are also present in the. atmosphere. These solid and liquid particles are of great climatic significance. Different constituents of the atmosphere with their individual characteristics, are discussed below.

Oxygen: Although this constituting only 21% of total volume of atmosphere, this is the most important component among gases. All living organisms inhale oxygen. Besides, oxygen can combine with other elements to form important compounds, such as, oxides. Also, combustion is not possible without oxygen.

Nitrogen: This accounts for 78% of total atmospheric volume. It is a relatively inert gas, and is an important constituent of all organic compounds. The main function of nitrogen is to control combustion by diluting oxygen thus it acts as a dilutant. It also indirectly helps in oxidation of different kinds.

Carbondioxide: This is the third important gas which constitutes only about 0.03% of the dry air and is a product of combustion. Green plants, through photosynthesis, absorb carbon dioxide from the atmosphere and use it to manufacture food and keep other bio-physical processes going. Being an efficient absorber of heat, carbon dioxide is considered to be of great climatic significance. Carbon dioxide is considered to be a very important factor in the heat energy budget. With increased burning of fossil fuels oil, coal and natural gas the carbon dioxide percentage in the atmosphere has been increasing at an alarming rate. More carbon dioxide in the atmosphere means more heat absorption. This could significantly raise the temperature at lower levels of the atmosphere thus inducing drastic climatic changes.

Ozone: is another important gas in the atmosphere, which is actually a type of oxygen molecule consisting of three, instead of two atoms. It forms less than 0.00005% by volume of the atmosphere and is unevenly distributed. It is between 20 km and 25 km altitude that the greatest concentrations of ozone are found. It is formed at higher altitudes and transported downwards. Ozone plays a crucial role in blocking the harmful ultraviolet radiation from the sun. Other gases found in almost negligible quantities in the atmosphere are argon, neon, helium, hydrogen, xenon, krypton, methane etc.

Water Vapour: this is one of the most variable gaseous substances present in atmosphere  constituting between 0.02% and 4% of the total volume in cold dry and humid tropical climates respectively. 90% of moisture content in the atmosphere exists within 6 km of the surface of the earth. Like carbon dioxide, water vapour .plays a significant role in the insulating action of the atmosphere. It absorbs not only the long- wave terrestrial radiation, but also a part of the incoming solar radiation. Water vapour is the source of precipitation and clouds. On condensation, it releases latent heat of condensation the ultimate driving force behind all storms. The moisture-carrying capacity of air is directly proportional to the air temperature.