Spectral observations of the sun and other stars in a study of the global changes of the earth's atmosphere

The possibility of using high-resolution spectral observations of the sun and other stars containing telluric lines for studying global changes in the composition of the earth's atmosphere and its other properties is discussed. This possibility is demonstrated using sun observations in the visible and near infrared ranges at the Moscow State University as an example. A comparison of the equivalent linewidths of O2 6295 A and CO2 20700 A, observed in 1969 and then in 1991-1993, indicates that, within the experimental uncertainty, the content of oxygen in the atmosphere over Moscow has not changed during the past 22-24 years, while the content of CO2 has increased substantially over the same period.