5.1E+18 kg - Total mass of Earth’s atmosphere (dry basis; average 1% H2O additional mass)
Analysis (mole fraction)
78.08% nitrogen (N2)
20.95% oxygen (O2)
9340 ppm argon (Ar) (10,000 ppm = 1%)
415 ppm carbon dioxide (CO2)*
18.2 ppm neon (Ne)
5.2 ppm helium (He)
1.7 ppm methane (CH4)
*419 ppm May 2021; annual increase 2.13 ppm/year => 422.7 February 2023
The Keeling Curve
Atmospheric mass of carbon dioxide per 1 ppm
= 5.1E+18 kg x ( 1E-06 ) x (1 tonne / 1000 kg)
= 5.1 E+09 tonne CO2 / 1 ppm CO2 = 5.1 Gt CO2 / 1 ppm CO2
Note, mole fraction means a proportion of the total gas based on the relative numbers of molecules of each gas. Because all gas molecules tend to behave identically point-like, the mole fraction is equal to the volume fraction. However, because molecules have different masses, the mole fraction and the mass fraction are not equal. From the atmospheric analysis above, and considering the relative masses of the molecules; the atmospheric MASS fractions of nitrogen, oxygen, argon and carbon dioxide (effective February 2023) are approximately 75.5%, 23.2%, 12900 ppm, and 640 ppm, respectively.