Which statement about GWP reference gas is true?

• A. It is R-12
• B. It is Carbon Dioxide
• C. It is Nitrogen
• D. It is Water Vapor

Answer: (B)

GWP is a scale that compares how much heat a greenhouse gas traps in the atmosphere over a specific period relative to carbon dioxide, which is assigned a GWP of 1 by definition. Because CO2 is the baseline, it is the GWP reference gas. Other gases, such as R-12 (a refrigerant with a much higher heat-trapping potential), have GWP values greater than 1. Nitrogen doesn’t act as a greenhouse gas in the same radiative forcing context, so it isn’t used as a reference gas. Water vapor is a major greenhouse gas too, but its concentration depends on temperature and it functions as a feedback rather than a fixed reference with a defined GWP. So, Carbon Dioxide is the GWP reference gas.