Comparability of CO2 measurements

In measuring the atmospheric CO₂ concentration, corrections for the carrier gas effect are required at present for each individual gas analyzer. It is shown that standard gases of CO₂/air composition offer less complication in the data comparison than CO₂/N₂ standards which are most commonly being used for calibration. CO₂/air standards which are used in Stockholm and related to the Scripps manometric calibration scale have remained stable over more than 10 years.

Aircraft data from the upper troposphere and the lower stratosphere obtained in the Stockholm project are in fair agreement with data from the Mauna Loa and the South Pole stations. An accelerating increase over the period 1963 to 1975, i.e. about 0.5 ppm/yr at the beginning and about 1.3 ppm/yr at the end of the period, has been observed.