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RAS question

Which of the following gases has the highest contribution to global warming?

Correct answer: (A) Carbon Dioxide (CO2).

Carbon dioxide has the highest contribution to global warming among the listed gases.

  1. (A)

    Carbon Dioxide (CO2)

  2. (B)

    Nitrous Oxide (N2O)

  3. (C)

    Chlorofluorocarbons (CFCs)

  4. (D)

    Methane (CH4)

Explanation

Carbon dioxide is the best answer because CO2 contributes about 76% of total greenhouse gas emissions, while the World Meteorological Organization calls it the single most important greenhouse gas in the atmosphere. Quantity matters: as long as emissions continue, CO2 keeps accumulating in the atmosphere and drives global temperature rise. Methane has a higher per-molecule warming potential, but the question asks for the highest overall contribution, not potency per molecule. On that measure, CO2 ranks above methane and nitrous oxide; WMO separately lists methane at about 19% and nitrous oxide at about 7% of the warming effect of long-lived greenhouse gases.

Why the other options are wrong

  • (B) Nitrous oxide is a powerful greenhouse gas, but WMO puts its share of radiative forcing by long-lived greenhouse gases at about 7%, well below carbon dioxide.
  • (C) Chlorofluorocarbons are not supported by WMO as the leading contributor; WMO identifies carbon dioxide as the single most important greenhouse gas.
  • (D) Methane has greater per-molecule warming potential, but its overall contribution is lower than carbon dioxide because CO2 is emitted and accumulated in much larger quantities.

Concept

This tests the Environment and Ecology concept of greenhouse gases and their relative contribution to global warming. It recurs in RAS because climate-change questions often distinguish overall contribution from per-molecule warming potential.

Source

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