Growth in stratospheric chlorine from short‐lived chemicals not controlled by the Montreal Protocol

We have developed a chemical mechanism describing the tropospheric degradation of chlorine containing very short‐lived substances (VSLS). The scheme was included in a global atmospheric model and used to quantify the stratospheric injection of chlorine from anthropogenic VSLS ( [Formula: see text]) between 2005 and 2013. By constraining the model with surface measurements of chloroform (CHCl(3)), dichloromethane (CH(2)Cl(2)), tetrachloroethene (C(2)Cl(4)), trichloroethene (C(2)HCl(3)), and 1,2‐dichloroethane (CH(2)ClCH(2)Cl), we infer a 2013 [Formula: see text] mixing ratio of 123 parts per trillion (ppt). Stratospheric injection of source gases dominates this supply, accounting for ∼83% of the total. The remainder comes from VSLS‐derived organic products, phosgene (COCl(2), 7%) and formyl chloride (CHClO, 2%), and also hydrogen chloride (HCl, 8%). Stratospheric [Formula: see text] increased by ∼52% between 2005 and 2013, with a mean growth rate of 3.7 ppt Cl/yr. This increase is due to recent and ongoing growth in anthropogenic CH(2)Cl(2)—the most abundant chlorinated VSLS not controlled by the Montreal Protocol.