Correct Option
The correct option is Nitrogen.
Explanation
Greenhouse gases (GHGs) are atmospheric constituents that absorb and emit radiant energy within the thermal infrared range. This property allows them to trap heat in the atmosphere, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere include water vapour, carbon dioxide, methane, nitrous oxide, and ozone.
Option Analysis
- Carbon dioxide (CO2): It is the primary long-lived greenhouse gas emitted through human activities and natural processes. It is radiatively active and contributes significantly to global warming.
- Methane (CH4): It is a potent greenhouse gas with a much higher heat-trapping capability per molecule than carbon dioxide, although it has a shorter atmospheric lifetime.
- Nitrous oxide (N2O): It is a significant greenhouse gas emitted from agricultural and industrial activities, as well as combustion of fossil fuels and solid waste.
- Nitrogen (N2): Nitrogen makes up approximately 78% of the Earth's atmosphere. It is a diatomic molecule with a symmetrical structure that renders it transparent to infrared radiation. Consequently, it does not trap heat and is not considered a greenhouse gas.
Key Takeaway: The major components of the atmosphere, Nitrogen (78%) and Oxygen (21%), are not greenhouse gases because they are transparent to infrared radiation. The greenhouse effect is driven by trace gases like CO2, CH4, and water vapour.