Compare the global warming potential (GWP) of methane (CH₄) and nitrous oxide (N₂O) over a 100‑year time horizon. State which gas has the higher GWP, give their approximate GWP values, and mention one major anthropogenic source for each gas.
Answer
Nitrous oxide has the higher GWP. Approximate GWP values: CH₄ ≈ 28, N₂O ≈ 298 (relative to CO₂ = 1) over 100 years. Major sources: CH₄ – rice cultivation and livestock digestion; N₂O – use of nitrogen‑based fertilizers in agriculture.
Step-by-step solution
- Recall that GWP is a measure of how much heat a gas traps compared to CO₂ over a specific period.
- Note the accepted 100‑year GWP values: CH₄ ≈ 28, N₂O ≈ 298.
- Compare the numbers: 298 (N₂O) is much larger than 28 (CH₄), so N₂O has the higher GWP.
- Identify a major anthropogenic source of CH₄: rice paddies and enteric fermentation in livestock.
- Identify a major anthropogenic source of N₂O: application of nitrogen‑based fertilizers in agriculture.
- Combine the information into a concise answer.
Common mistake: Confusing GWP values with atmospheric concentration; students may quote CO₂ levels instead of GWP numbers.
Concept tested: GWP comparison of greenhouse gases
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