Stratospheric lifetime ratio of CFC-11 and CFC-12 from satellite and model climatologies

Abstract

Chlorofluorocarbons (CFCs) play a key role in stratospheric ozone loss and are strong infrared absorbers that contribute to global warming. The stratospheric lifetimes of CFCs are a measure of their stratospheric loss rates that are needed to determine global warming and ozone depletion potentials. We applied the tracer-tracer correlation approach to zonal mean climatologies from satellite measurements and model data to assess the lifetimes of CFCl3 (CFC-11) and CF2Cl2 (CFC-12).We present estimates of the CFC-11 = CFC-12 lifetime ratio and the absolute lifetime of CFC-12, based on a reference lifetime of 52 years for CFC- 11. We analyzed climatologies from three satellite missions, the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), the HIgh Resolution Dynamics Limb Sounder (HIRDLS), and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). We found a CFC-11 = CFC-12 lifetime ratio of 0:47±0:08 and a CFC- 12 lifetime of 112(96-133) years for ACE-FTS, a ratio of 0:46±0:07 and a lifetime of 113(97-134) years for HIRDLS, and a ratio of 0:46±0:08 and a lifetime of 114(98-136) years for MIPAS. The error-weighted, combined CFC-11 = CFC-12 lifetime ratio is 0:46±0:04 and the CFC-12 lifetime estimate is 113(103-124) years. These results agree with the recent Stratosphere-troposphere Processes And their Role in Climate (SPARC) reassessment, which recommends lifetimes of 52(43-67) years and 102(88-122) years, respectively. Having smaller uncertainties than the results from other recent studies, our estimates can help to better constrain CFC-11 and CFC-12 lifetime recommendations in future scientific studies and assessments. Furthermore, the satellite observations were used to validate first simulation results from a new coupled model system, which integrates a Lagrangian chemistry transport model into a climate model. For the coupled model we found a CFC-11 = CFC-12 lifetime ratio of 0:48±0:07 and a CFC-12 lifetime of 110(95-129) years, based on a 10-year perpetual run. Closely reproducing the satellite observations, the new model system will likely become a useful tool to assess the impact of advective transport, mixing, and photochemistry as well as climatological variability on the stratospheric lifetimes of long-lived tracers.