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

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posted on 2016-12-15, 09:55 authored by R. Hossaini, M. P. Chipperfield, A. Saiz-Lopez, J. J. Harrison, R. von Glasow, R. Sommariva, E. Atlas, M. Navarro, S. A. Montzka, W. Feng, S. Dhomse, C. Harth, J. Muehle, C. Lunder, S. O'Doherty, D. Young, S. Reimann, M. K. Vollmer, P. B. Krummel, P. F. Bernath
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 (ClVSLS y ) between 2005 and 2013. By constraining the model with surface measurements of chloroform (CHCl3), dichloromethane (CH2Cl2), tetrachloroethene (C2Cl4), trichloroethene (C2HCl3), and 1,2-dichloroethane (CH2ClCH2Cl), we infer a 2013 ClVSLS y 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 (COCl2, 7%) and formyl chloride (CHClO, 2%), and also hydrogen chloride (HCl, 8%). Stratospheric ClVSLS y 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 CH2Cl2—the most abundant chlorinated VSLS not controlled by the Montreal Protocol.


We thank the Natural Environment Research Council (NERC) for funding through the TropHAL project (NE/J02449X/1 and NE/J022780/1). We thank Ron Prinn, Ray Weiss, and their AGAGE colleagues for data access. AGAGE is supported principally by NASA (USA) grants to MIT and SIO and also by DECC (UK) and NOAA (USA) grants to Bristol University; CSIRO and BoM (Australia); Empa (Switzerland); and NILU (Norway). S.A.M. acknowledges the technical assistance of C. Siso, B. Miller, and B. Hall and support, in part, from NOAA Climate Program Office's AC4 Program. The ACE mission is supported by the Canadian Space Agency.



Geophysical Research Letters, 2015, 42 (11), pp. 4573-4580 (8)

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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Geophysical Research Letters


American Geophysical Union (AGU), Wiley





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Model output data presented here are available on request. Surface observation data are given in the supporting information.