Abstract: Spectral measurements of the outgoing thermal IR radiation carried out in 1977 and 1979 (SI-1 instrument, Meteor satellite) are used for estimating the CO ₂ content in the Earth’s atmosphere. A special algorithm based on the technique of artificial neural networks has been developed for solving the inverse problem of determining the CO ₂ content. The algorithm uses experimental spectra, as well as data on temperature and humidity from the NCEP CFSR reanalysis archive. Despite the presence of a noticeable variation in individual values of CO ₂ content in 1977 and 1979 (330–350 ppm), the estimates clearly demonstrate the seasonal variations of the carbon dioxide content for Europe and low values for the Southern Hemisphere. The spatial and temporal averaging of the retrieved CO ₂ estimates gives mean winter and spring–summer values for the European region at 338.2 and 336.5 ± 3.1 ppmv, correspondingly, which is in a good agreement with the ground-based measurements at Mauna Loa station.