State the rough composition of the atmosphere today.

78% Nitrogen, 21% Oxygen, 1% other gases

In our atmosphere today, there are the following gases:

Nitrogen ( ~ 78%)

Oxygen ( ~ 21)

Carbon dioxide, Water Vapour & Noble Gases (in total 1%)

The composition of the Earth’s atmosphere (as dry air, because it contains varying amounts of water), is roughly 78% nitrogen, 21% oxygen. The remaining 1%, is composed of about 0.9% argon (the most common noble gas). The other noble gases, (i.e. helium, neon, krypton, xenon and radon), together with other gases make up the remaining 0.1%. Note, carbon dioxide currently makes up just 0.04% of the atmosphere, but its level is rising. (It has risen from 0.029% to 0.040% in the last 100 years, that is a rise of 27.5%. A rise in the Earth’s average temperature in the same period of >1 deg C, gives evidence of global warming by the Greenhouse Effect.)