Which statement best describes non-CO2 greenhouse gases like methane and nitrous oxide?

• A. They have high radiative forcing and significant short-term climate effects compared to CO2 per molecule.
• B. They are less important than CO2 and have no radiative forcing.
• C. They are not produced by agriculture.
• D. They remain in the atmosphere for hundreds of years equally to CO2.

Answer: (A)

Non-CO2 greenhouse gases such as methane and nitrous oxide are incredibly potent on a per-molecule basis because they trap more infrared energy per molecule than CO2. That high radiative efficiency means they drive strong warming in the near term, even if their overall atmospheric amounts are smaller than CO2. Methane, for example, has a very large short-term warming impact (high radiative forcing) but a relatively short atmospheric lifetime, while nitrous oxide is also highly effective per molecule and persists longer. Together, this means they can produce significant climate effects on decadal timescales, which is why the statement describing high radiative forcing and notable short-term climate effects per molecule is the best description. The other choices misstate these gases’ origins or their climate impact; methane and nitrous oxide are produced in agriculture, they do contribute radiative forcing, and their lifetimes differ from CO2's, so they do not persist in the atmosphere for hundreds of years in the same way CO2 does.