Which one among the following is not a greenhouse gas?

Greenhouse gases (GHGs) are atmospheric gases that absorb and re-emit infrared radiation, thereby trapping heat in the atmosphere. The primary GHGs include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and chlorofluorocarbons (CFCs) [5]. While ozone in the stratosphere protects against UV radiation, it acts as a potent greenhouse gas when present in the troposphere [1]. CFCs are synthetic industrial chemicals that contribute significantly to global warming alongside their role in ozone depletion [5]. Sulphur dioxide (SO2), however, is primarily an air pollutant derived from natural sources or industrial activities [4]. Unlike GHGs, SO2 often leads to the formation of aerosols that can have a cooling effect by reflecting sunlight, and it is not classified as a greenhouse gas in standard climate assessments [4]. Therefore, sulphur dioxide is the correct answer as it does not trap terrestrial radiation.

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > Greenhouse Gases(GHGs) > p. 96
2. [5] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > 2. greenhouse gases > p. 9
3. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > 2. greenhouse gases > p. 11
4. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > 20.1. Composition of The Earth's Atmosphere > p. 270
5. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 29: Environment Issues and Health Effects > Greenhouse gases (GHGS) > p. 426