Nitrogen makes up about 78% of Earth’s atmosphere but is not a greenhouse gas. In dry air, nitrogen gas (N₂) accounts for approximately 78.1% by volume, making it the atmosphere’s most abundant component. Oxygen follows at about 20.9%, while argon contributes roughly 0.93%. Carbon dioxide and other trace gases make up much smaller fractions.
Nitrogen does not significantly absorb Earth’s outgoing infrared radiation because its two-atom molecules are electrically symmetrical. Greenhouse gases such as carbon dioxide, methane, and water vapor have molecular structures that can absorb and re-emit infrared energy, helping warm the lower atmosphere.
A common mix-up is assuming that the most abundant gases must also have the strongest climate effects. Atmospheric abundance and greenhouse strength are different properties. Nitrogen is essential to the nitrogen cycle and becomes biologically useful after fixation by certain bacteria or industrial processes, but it does not directly drive the natural greenhouse effect. Argon and oxygen are also not significant greenhouse gases.