RAS question
Which greenhouse gas has the highest Global Warming Potential (GWP) per molecule?
Correct answer: (B) Sulfur hexafluoride (SF6).
Sulfur hexafluoride (SF6) has the highest Global Warming Potential among the listed greenhouse gases, with a 100-year GWP of about 23,500 relative to carbon dioxide.
Explanation
Sulfur hexafluoride (SF6) is the right answer because GWP compares how effectively a greenhouse gas traps heat relative to carbon dioxide, which is assigned a GWP of 1. The given values put SF6 far above the other options: about 23,500 over 100 years, compared with nitrous oxide at about 265 and methane at about 28. EPA also describes SF6 as the most potent greenhouse gas known and notes that, over a 100-year period, it is 23,500 times more effective at trapping infrared radiation than an equivalent amount of CO2. Its practical relevance is not abstract: SF6 is used in electric power systems, including circuit breakers, gas-insulated substations and other switchgear.
Why the other options are wrong
- (A) Nitrous oxide has a 100-year GWP of about 265, which is significant but still far below SF6 at about 23,500.
- (C) Methane has a 100-year GWP of about 28, so it does not approach the heat-trapping potency of SF6.
- (D) Carbon dioxide is the reference gas for GWP calculations and is assigned a value of 1, not the highest value.
Concept
This tests the Environment and Ecology concept of greenhouse gases and Global Warming Potential. It recurs in RAS because climate-change questions often ask candidates to compare gases by potency, not just by familiarity or emission volume.