- The proportion of gases in the air has not changed much in 200 million years
- About four fifths of the air is nitrogen and one fifth is oxygen
- The remaining gases include carbon dioxide, water vapour and trace quantities of the noble gases
Pie chart showing the composition of clean air
- Scientists know the historic composition of the air by analysing the tiny air bubbles trapped in ice cores taken at the poles
- The air bubbles were trapped as the snow and ice was laid down tens of thousands of years ago and provide a snapshot of what our atmosphere was like back then
Although the proportion of carbon dioxide is very small, it plays a substantial role in global warming as a greenhouse gas.