Which one among the following gases has the highest Global Warming Potential…
2025
Which one among the following gases has the highest Global Warming Potential (GWP) ?
Answer: B. Nitrous Oxide (N2O) — Concept. Global Warming Potential (GWP) measures how much heat one kilogram of a gas traps in the atmosphere over a fixed time horizon — conventionally 100…
- A.
Sulphur dioxide (SO2)
- B.
Nitrous Oxide (N2O)
- C.
Methane (CH4)
- D.
Carbon dioxide (CO2)
Show answer & explanation
Correct answer: B
Concept. Global Warming Potential (GWP) measures how much heat one kilogram of a gas traps in the atmosphere over a fixed time horizon — conventionally 100 years — relative to one kilogram of carbon dioxide. Two molecular properties decide the value: how strongly the molecule absorbs outgoing infrared radiation, and how long it survives in the atmosphere before it is destroyed or removed. Carbon dioxide is the reference gas of the scale, so its GWP is 1 by definition, and any gas that is both a strong infrared absorber and long-lived scores far above it.
Applying the concept to the gases offered
First ask whether each gas is a greenhouse gas at all. Sulphur dioxide (SO2) is scavenged from the air within days and converts to sulphate aerosols, which scatter sunlight and exert a net cooling effect, so the IPCC assigns it no GWP and it is not part of the Kyoto basket of greenhouse gases.
Fix the baseline. Carbon dioxide (CO2) defines the scale itself, so its 100-year GWP is exactly 1.
Compare the two remaining long-lived gases using the IPCC AR6 100-year values: methane (CH4) is about 27–30, while nitrous oxide (N2O) is about 273. Methane absorbs infrared strongly but is oxidised within roughly a decade, whereas nitrous oxide absorbs strongly and survives about a century, so the heat it traps accumulated over the 100-year horizon is an order of magnitude larger.
Therefore, among the gases offered, nitrous oxide (N2O) has the highest Global Warming Potential.
Cross-check: lifetime and 100-year GWP
Gas | Atmospheric removal timescale | 100-year GWP (IPCC AR6) |
|---|---|---|
Nitrous oxide (N2O) | About 110 years | 273 |
Methane (CH4) | About 12 years | 27–30 |
Carbon dioxide (CO2) | No single lifetime; removed over decades to millennia by ocean and biosphere uptake | 1 (reference gas) |
Sulphur dioxide (SO2) | A few days | Not assigned (aerosol precursor, net cooling) |
The ranking does not depend on which IPCC assessment report is used: AR4 lists 298 for nitrous oxide against 25 for methane, AR5 lists 265 against 28, and AR6 lists 273 against 27.9. Nitrous oxide stays roughly ten times above methane in every assessment.
Note that industrial fluorinated gases such as sulphur hexafluoride (SF6), with a 100-year GWP near 25,000, rank far higher still, but none of them appears among the gases listed in this question.
Answer: Nitrous oxide (N2O).