Table 1.1

Table 1.1. Principal gases of the present-day atmosphere near the Earth's surface

PERMANENT GASES
Gas	Symbol	Percent (by volume, dry air)
Nitrogen	N₂	78.08
Oxygen	O₂	20.95
Argon	Ar	0.93
Neon	Ne	0.0018

VARIABLE GASES

Gas Symbol Percent (by volume, dry air)

Water Vapor H₂O 0 to 4

Carbon Dioxide CO₂ 0.036

Methane CH₄ 0.00017

Nitrous Oxide N₂O 0.00003

VARIABLE GASES
Gas	Symbol	Percent (by volume, dry air)
Water Vapor	H₂O	0 to 4
Carbon Dioxide	CO₂	0.036
Methane	CH₄	0.00017
Nitrous Oxide	N₂O	0.00003