Science Update: Stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O from ACE-FTS observations

A.T. Brown and co-authors use measurements from the ACE-FTS satellite instrument to calculate the stratospheric lifetimes of CFC-12, CCl4, CH4, CH3Cl and N2O in a recent ACP article. The lifetimes are calculated using the slope of the tracer–tracer correlation of these species with CFC-11 (assuming a lifetime of 45 years) at the tropopause. The correlation slopes are corrected for changing atmospheric concentrations based on the age-of-air and CFC-11 measurements from samples taken aboard the Geophysica aircraft – along with the effective linear trend of the volume mixing ratio (VMR) from tropical ground based AGAGE (Advanced Global Atmospheric Gases Experiment) sites. Calculated lifetimes are: 113 +(−) 26(18) years [CFC-12], 35 +(−) 11(7) years [CCl4], 69 +(−) 65(23) years [CH3Cl], 123 +(−) 53(28) years [N2O], and 195 +(−) 75(42) years [CH4]. The errors on these values are the weighted 1σ non-systematic errors. For CH3Cl & CH4 this represents the first calculation of the stratospheric lifetime using data from a space-based instrument. The full abstract can be found here.