Question

Which among these is not a greenhouse gas?

• A. Water vapour
• B. Carbon-dioxide
• C. Hydrogen
• D. Ozone

Hint:

Greenhouse gases play a major role in climate change by trapping heat in the atmosphere. Understanding them helps in addressing global warming.

Answer 1

The Correct Option is C

Greenhouse gases work by absorbing infrared (heat) radiation, something only molecules with three or more atoms, or asymmetric structures, can do effectively, which is why water vapour, carbon dioxide and ozone all qualify.

Hydrogen is a simple, symmetric two-atom molecule with no net dipole, so it does not absorb infrared radiation and cannot trap heat, meaning it does not act as a greenhouse gas at all.

Therefore, the correct answer is Hydrogen.

Answer 2

Cross-checking against the standard list of greenhouse gases recognized in climate science reports (like those of the IPCC) also gives the same result.

1. Water vapour: Explicitly listed as the most abundant natural greenhouse gas in atmospheric science.
2. Carbon-dioxide: Explicitly listed as the primary anthropogenic greenhouse gas tracked in climate agreements.
3. Hydrogen: Not included on standard greenhouse gas inventories at all; it is instead discussed as a clean fuel, and any indirect climate effect it has is through atmospheric chemistry, not direct heat-trapping.
4. Ozone: Explicitly listed as a greenhouse gas in the troposphere, alongside its separate, well-known role in the stratospheric ozone layer.

Since hydrogen never appears on standard greenhouse gas lists while the other three consistently do, hydrogen is the correct exception.

Therefore, the correct answer is Hydrogen.