Gaseous composition of dry air and their vertical distribution

Table 4.1 Gaseous composition of dry air

Gaseous composition of dry air
(Trace gases are given the unit of part per million (ppm)).

Types Mole percent
Nitrogen (N2) 78.084
Oxygen (O2) 20.947
Argon (Ar) 0.934
Carbon Dioxide (CO2)
400 ppm
Neon (Ne)
18.2 ppm
Helium (He)
5.24 ppm
Methane (CH4)
1.83 ppm
Krypton (Kr)
1.14 ppm
Hydrogen (H)
0.51 ppm
Nitrous oxide (N2O)
0.32 ppm
Xenon (Xe)
0.087 ppm
Ozone (O3)
trace to 8 ppm
Carbon monoxide (CO)
trace to 0.25 ppm
Sulfur dioxide (SO2)
trace to 0.1 ppm
Nitrogen dioxide (NO2)
trace to 0.02 ppm
Ammonia (NH3)
trace to 0.003 ppm


Greenhouse Gases:
a greenhouse gas is any gas species in the atmosphere that absorbs infrared radiation from the Earth's surface, producing the so-called "greenhouse effect" which warms the atmosphere and reduce the heat loss of the Earth's surface.

Key Greenhouse Gases Influenced by Human Activities
Parameter CO2 CH4 CFC-11 (CFCl3) CFC-12 (CF2Cl2) N2O
Pre-industrial atmospheric concentration (1750-1800) 280 ppmv 0.8 ppmv 0 0 288 ppbv
Current atmospheric concentration (2015) 400 ppmv 1.83 ppmv 240 pptv2 530 pptv 320 ppbv
Atmospheric lifetime (years) (50-200) 10 65 130 150
Radiative forcing factors 1 21 12400 15800 206

Vertical distribution of some greenhouse gases

Vertical distribution of Aerosols