On the regional and seasonal ozone depletion potential of chlorinated very short-lived substances

Chloroform (CHCl3), dichloromethane (CH2Cl2), perchloroethylene (C2Cl4) and 1,2-dichloroethane (C2H4Cl2) are chlorinated Very Short-Lived Substances (Cl-VSLS) with a range of commercial/industrial applications. Recent studies highlight the increasing influence of Cl-VSLS on the stratospheric chlorine budget and therefore their possible role in ozone depletion. Here, we evaluate the ozone depletion potential (ODP) of these Cl-VSLS using a three-dimensional chemical transport model and investigate sensitivity to emission location/season. The seasonal dependence of the ODPs is small but ODPs vary by a factor of 2-3 depending on the continent of emission: 0.0143-0.0264 (CHCl3), 0.0097-0.0208 (CH2Cl2), 0.0057-0.0198 (C2Cl4) and 0.0029-0.0119 (C2H4Cl2). Asian emissions produce the largest ODPs owing to proximity to the tropics and efficient troposphere-to-stratosphere transport of air originating from industrialised East Asia. The Cl-VSLS ODPs are generally small but the upper ends of the CHCl3 and CH2Cl2 ranges are comparable to the mean ODP of methyl chloride (0.02), a longer-lived ozone-depleting substance.