The impact of various gases on global warming is quantified by their Global Warming Potential (GWP) and atmospheric concentrations. The gases under consideration are N2O, NO2, CFCs, and CH4. Their individual contributions to global warming vary:
- N2O (Nitrous Oxide): Possesses a high GWP and is a significant contributor to global warming.
- CH4 (Methane): Exhibits a high GWP. Although less prevalent than CO2, its overall impact is substantial, though less than that of CO2.
- CFCs (Chlorofluorocarbons): Demonstrate an extremely high GWP, functioning as potent greenhouse gases. Their use is strictly controlled due to their damaging effect on the ozone layer.
- NO2 (Nitrogen Dioxide): Is primarily recognized as an air pollutant affecting human health and visibility, with a minimal direct contribution to global warming.
Based on these factors, NO2 accounts for the smallest percentage of total global warming among the listed gases.
Consequently, the correct identification is: NO2