Decrease in CO2 mixing ratio observed in the stratosphere

Air samples, collected cryogenically at different heights of the stratosphere, were analysed for carbon dioxide with an IR absorption technique. Supplementary tropospheric air samples were taken aboard commercial airliners. The results reported here show that the CO2 mixing ratio is not constant with altitude but rather decreases in the stratosphere, by about 7 p.p.m.v., between the tropopause and 33 km. One conclusion is that recently increased concentrations of CO2 in the troposphere have not propagated far into the stratosphere.