Question

Which of the following gases give the lowest percentage contribution to total global warming?

• A. N2O
• B. NO2
• C. CFCs
• D. CH4

Answer 1

The Correct Option is B

The contribution of different gases to global warming is measured by their Global Warming Potential (GWP) and their concentrations in the atmosphere. The options given include N₂O, NO₂, CFCs, and CH₄. Each of these gases contributes to global warming in different ways and to varying extents: 

• N₂O (Nitrous Oxide): Has a relatively high GWP and contributes significantly to global warming.
• CH₄ (Methane): Has a high GWP but is less abundant than CO₂, making its impact significant but smaller than CO₂ in total.
• CFCs (Chlorofluorocarbons): Have an exceedingly high GWP and are powerful greenhouse gases, albeit regulated heavily due to their detrimental effects on the ozone layer.
• NO₂ (Nitrogen Dioxide): Primarily a pollutant with consequences for human health and visibility rather than a major direct contributor to global warming. 

Considering these facts, NO₂ gives the lowest percentage contribution to total global warming compared to the other gases listed.

Therefore, the correct answer is: NO₂

Answer 2

The gas that gives the lowest percentage contribution to total global warming is NO₂ (Nitrogen Dioxide).

Additional Context:

• Global Warming Contributions:
  • CO₂: ~76% of total (not listed in options)
  • CH₄ (Methane): ~16% (high warming potential but shorter lifespan)
  • N₂O (Nitrous Oxide): ~6% (long atmospheric lifetime)
  • CFCs: ~1-2% (declining due to Montreal Protocol)
  • NO₂: <1% (short-lived, indirect effects)
• Key Properties:
  • NO₂:
    • Atmospheric lifetime: Hours to days
    • Indirectly affects warming via ozone formation
    • Primarily an air pollutant, not major GHG
  • Other gases:
    • N₂O: 114-year lifetime, 298x CO₂ potency
    • CFCs: 50-500 year lifetime, 1000s x CO₂ potency
    • CH₄: 12-year lifetime, 28x CO₂ potency
• Measurement Sources:
  • IPCC AR6 (2021) assessments
  • NOAA's Annual Greenhouse Gas Index
• Climate Impact Pathways:
  • NO₂ contributes more to:
    • Photochemical smog
    • Acid rain formation
    • Tropospheric ozone production

Correct Answer: (2) NO₂.