The 'age' of stratospheric air is a measure that characterizes the time scales of stratospheric transport. In this work we present and compare age-values as determined from measurements of CO2 and SF6 on air-samples obtained between 1987 and 1995 on six flights of our balloon-borne cryo-sampler. In the middle stratosphere for five out of six flights we find age-values that are up to three years lower for CO2 than for SF6. This CO2-age anomaly corresponds to an excess of 4--5 ppm CO2. Evidence is presented that this excess-CO2 originates from rapid convective transport of near surface air. Additionally, we show that globally no compact relationship exists between the age of air and mixing-ratios of N2O. ¿ 1998 American Geophysical Union