Abstract
Although atmospheric composition has varied over very long time scales, today's atmosphere is essentially made up of nitrogen (N2) and oxygen (O2). The impact of human activity on the concentration of these gases is measurable but negligible. The gases that influence climate change are present in trace amounts in the atmosphere, which is why anthropogenic emissions have had an influence on their concentration. How do we know the composition of the atmosphere today and in the past ? How has this composition evolved naturally or as a result of human activity ?
