Question

The correct ascending order of the following greenhouse gases with respect to their global warming potential relative to CO$_2$ in the time horizon of 100 years is:
- CH$_4$
- N$_2$O
- CFCl$_3$
- CF$_2$Cl$_2$

• A. CH$_4 < N$_2$O < CFCl$_3 < CF$_2$Cl$_2$
• B. CF$_2$Cl$_2 < CH$_4 < N$_2$O < CFCl$_3$
• C. CH$_4 < N$_2$O < CF$_2$Cl$_2 < CFCl$_3$
• D. N$_2$O < CFCl$_3 < CH$_4 < CF$_2$Cl$_2$

Hint:

- CH$_4$: short-lived, moderate GWP.
- N$_2$O: long-lived, higher GWP.
- CFCs: extremely high GWP due to long atmospheric lifetimes.
Mnemonic: CH$_4$<N$_2$O<CFC-11<CFC-12.

Answer 1

The Correct Option is A

Step 1: Recall GWP values (100-year horizon).
- CH$_4$ ≈ 28–30 times CO$_2$
- N$_2$O ≈ 265–300 times CO$_2$
- CFCl$_3$ (CFC-11) ≈ 4660 times CO$_2$
- CF$_2$Cl$_2$ (CFC-12) ≈ 10,200 times CO$_2$

Step 2: Arrange in ascending order.
CH$_4$ (≈30) < N$_2$O (≈265) < CFCl$_3$ (≈4660) < CF$_2$Cl$_2$ (≈10,200).
Step 3: Match with options.
This corresponds to Option (C). Final Answer: \[ \boxed{\text{(C) CH$_4 < N$_2$O < CF$_2$Cl$_2 < CFCl$_3$}} \]