Question

Which one or more of the following is/are greenhouse gas(es)?

• A. Methane
• B. Water vapour
• C. Sulphur dioxide
• D. Nitrous oxide

Hint:

Common greenhouse gases to remember for GATE Ecology: {CO$_2$, CH$_4$, N$_2$O, and H$_2$O}. Gases like SO$_2$ mainly cause cooling via aerosols, not greenhouse warming.

Answer 1

The Correct Option is A

Step 1: Recall the definition of greenhouse gases.
Greenhouse gases are atmospheric gases that absorb and emit infrared radiation, thereby trapping heat in the Earth’s atmosphere and contributing to the greenhouse effect.
Step 2: Analyze option (A) — Methane.
Methane (CH$_4$) is a major greenhouse gas with a high global warming potential.
It absorbs infrared radiation effectively and contributes significantly to climate change.
Hence, (A) is correct.
Step 3: Analyze option (B) — Water vapour.
Water vapour (H$_2$O) is the most abundant greenhouse gas in the atmosphere.
It plays a crucial role in regulating Earth’s temperature through strong absorption of infrared radiation.
Hence, (B) is correct.
Step 4: Analyze option (C) — Sulphur dioxide.
Sulphur dioxide (SO$_2$) primarily contributes to aerosol formation and has a cooling effect by reflecting sunlight.
It is not considered a greenhouse gas.
Hence, (C) is incorrect.
Step 5: Analyze option (D) — Nitrous oxide.
Nitrous oxide (N$_2$O) is a potent greenhouse gas with a long atmospheric lifetime.
It absorbs infrared radiation and contributes to global warming.
Hence, (D) is correct.
Step 6: Conclusion.
The gases that act as greenhouse gases among the given options are: \[ \boxed{(A),\ (B)\ \text{and}\ (D)} \]