Previous Year Question

Greenhouse Gases (GHGs) are atmospheric gases that absorb and re-emit Infrared Radiation emitted from the Earth's surface, contributing to the warming of the lower atmosphere. Major naturally occurring greenhouse gases include Water Vapour (H₂O), Carbon Dioxide (CO₂), Methane (CH₄), Nitrous Oxide (N₂O), and Ozone (O₃). Among these, water vapour plays an important role in the natural Greenhouse Effect.

Nitrogen Oxides (NOₓ) generally refer to a group of compounds consisting mainly of Nitric Oxide (NO) and Nitrogen Dioxide (NO₂). They are primarily produced by high-temperature combustion in vehicles, thermal power plants, and industrial processes. NOₓ are not classified as direct greenhouse gases. However, they contribute to the formation of Ground-level Ozone through atmospheric chemical reactions and can indirectly influence the climate.

Carbon Dioxide (CO₂), Methane (CH₄), and Ozone (O₃) are all naturally occurring greenhouse gases. CO₂ is released through natural respiration, decomposition of organic matter, and volcanic activity. Methane is produced by natural wetlands and microbial processes. Ozone in the Stratosphere absorbs harmful Ultraviolet (UV) Radiation from the Sun, whereas in the Troposphere, it acts as both a greenhouse gas and an air pollutant.

It is essential to distinguish between Nitrogen Oxides (NOₓ) and Nitrous Oxide (N₂O). Nitrous Oxide is a powerful greenhouse gas naturally produced through microbial processes in soils and oceans. In contrast, NO and NO₂ are primarily considered air pollutants. NOₓ can also originate from natural sources, including lightning and biological processes in soils, but this does not make them major direct greenhouse gases. In the examination question, Nitrogen Oxide refers to NOₓ, not N₂O.