Nitrous oxide is the third most important anthropogenic greenhouse gas after CO₂ and methane. Its Global Warming Potential (GWP) over a 100-year timeframe is 273, meaning one tonne of N₂O has the same warming effect as 273 tonnes of CO₂ over a century.
Why Such High GWP?
N₂O absorbs infrared radiation in atmospheric windows where CO₂ is less effective. It has strong absorption bands at 7.8 μm and 17 μm wavelengths. Additionally, N₂O has an atmospheric lifetime of approximately 109 years — far longer than methane (12 years), meaning each molecule contributes to warming for over a century.
Radiative Forcing
Current N₂O concentrations (336 ppb in 2024) contribute approximately 0.21 W/m² of radiative forcing — about 6% of total anthropogenic forcing. The concentration has increased from pre-industrial levels of ~270 ppb, driven primarily by agricultural fertilizer use.