Question

Arrange the following greenhouse gases in decreasing order of their contribution to total global warming.
A. Nitrous oxide
B. Carbon dioxide
C. Chlorofluoro carbon
D. Methane

• A. C, A, B, D
• B. A, C, B, D
• C. A, B, C, D
• D. B, D, A, C

Hint:

Don't confuse Global Warming Potential (GWP) with overall contribution. While a molecule of methane is more potent than a molecule of CO\(_2\), there are far more CO\(_2\) molecules in the atmosphere, making its total effect the largest.

Answer 1

The Correct Option is D

Step 1: Define "global warming contribution". This is determined by a gas's atmospheric concentration and its global warming potential (GWP) per molecule. The total impact is the product of these values.

Step 2: Order gases by their overall impact.1. Carbon Dioxide (CO\(_2\)): Although CO\(_2\) has the lowest GWP (GWP=1), its high atmospheric concentration makes it the largest contributor to modern global warming (typically over 60%).2. Methane (CH\(_4\)): Methane has a higher GWP than CO\(_2\) but a lower concentration, making it the second-largest contributor.3. Nitrous Oxide (N\(_2\)O): Despite a high GWP and long atmospheric lifetime, its lower concentration ranks it as the third-largest contributor.4. Chlorofluorocarbons (CFCs) and other halocarbons: These have extremely high GWPs but very low concentrations, resulting in a smaller overall contribution.

Step 3: Establish the sequence.The decreasing order of contribution is: B (Carbon dioxide) \(\rightarrow\) D (Methane) \(\rightarrow\) A (Nitrous oxide) \(\rightarrow\) C (Chlorofluorocarbon).The sequence is B, D, A, C.