The greenhouse gas that is known to contribute the least amount to global warming is ___________.

The correct answer is nitrous oxide.

Key Points

• Nitrous oxide (N₂O) is a greenhouse gas that contributes the least to global warming compared to other major greenhouse gases like carbon dioxide (CO₂), methane (CH₄), and chlorofluorocarbons (CFCs).
• Nitrous oxide accounts for a smaller portion of total greenhouse gas emissions globally, with its contribution being around 6% of all greenhouse gases.
• Despite its relatively low concentration, nitrous oxide has a Global Warming Potential (GWP) of approximately 298 times higher than CO₂ over a 100-year period, but its overall effect is less due to its lower abundance.
• Nitrous oxide is primarily emitted from agricultural activities such as the use of synthetic fertilizers, as well as other sources like the burning of fossil fuels and certain industrial processes.
• It has a relatively long atmospheric lifetime of about 114 years, but its total emissions are much less than those of carbon dioxide and methane.
• Efforts to reduce nitrous oxide emissions include optimizing fertilizer use in agriculture and improving industrial processes to minimize emissions.

 Additional Information

• Carbon dioxide (CO₂)
  • Carbon dioxide is the most abundant greenhouse gas responsible for global warming, contributing around 76% of total greenhouse gas emissions.
  • It is emitted primarily through the burning of fossil fuels (coal, oil, and gas), deforestation, and industrial processes.
  • It has a relatively low Global Warming Potential (GWP) of 1, but its sheer abundance makes it the largest contributor to global warming.
• Methane (CH₄)
  • Methane is a highly potent greenhouse gas with a Global Warming Potential (GWP) of around 25 times that of CO₂ over a 100-year period.
  • It is produced from sources such as livestock digestion (enteric fermentation), rice paddies, and the decomposition of organic matter in landfills.
  • Methane has a much shorter atmospheric lifetime of about 12 years but is a major contributor to global warming due to its high GWP.
• Chlorofluorocarbons (CFCs)
  • CFCs are synthetic compounds used primarily in refrigeration, air conditioning, and aerosol propellants.
  • They are potent greenhouse gases with a Global Warming Potential (GWP) in the thousands, but their emissions have been largely phased out under the Montreal Protocol due to their role in ozone layer depletion.
  • Although their emissions are now limited, their long atmospheric lifetimes allow them to persist and contribute to warming for decades.