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

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 Mühle; C Lunder; S O'Doherty; D Young; S Reimann; M K Vollmer; P B Krummel; P F Bernath

doi:10.1002/2015GL063783

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

Geophys Res Lett. 2015 Jun 16;42(11):4573-4580. doi: 10.1002/2015GL063783. Epub 2015 Jun 1.

Authors

R Hossaini¹, M P Chipperfield¹, A Saiz-Lopez², J J Harrison³, R von Glasow⁴, R Sommariva⁵, E Atlas⁶, M Navarro⁶, S A Montzka⁷, W Feng⁸, S Dhomse¹, C Harth⁹, J Mühle⁹, C Lunder¹⁰, S O'Doherty¹¹, D Young¹¹, S Reimann¹², M K Vollmer¹², P B Krummel¹³, P F Bernath¹⁴

Affiliations

¹ School of Earth and Environment University of Leeds Leeds UK.
² Atmospheric Chemistry and Climate Group Institute of Physical Chemistry Rocasolano, CSIC Madrid Spain.
³ National Centre for Earth Observation, Department of Physics and Astronomy University of Leicester Leicester UK.
⁴ Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences University of East Anglia Norwich UK.
⁵ Centre for Ocean and Atmospheric Sciences, School of Environmental SciencesUniversity of East AngliaNorwichUK; Now at Department of ChemistryUniversity of LeicesterLeicesterUK.
⁶ Rosenstiel School of Marine and Atmospheric Science University of Miami Miami Florida USA.
⁷ National Ocean and Atmospheric Administration Boulder Colorado USA.
⁸ National Centre for Atmospheric Science University of Leeds Leeds UK.
⁹ Scripps Institution of Oceanography University of California San Diego California USA.
¹⁰ Monitoring and Information Technology Department Norwegian Institute for Air Research Kjeller Norway.
¹¹ Atmospheric Chemistry Research Group, School of Chemistry University of Bristol Bristol UK.
¹² Swiss Federal Laboratories for Materials Science and Technology Dübendorf Switzerland.
¹³ Oceans and Atmosphere Flagship CSIRO Aspendale Victoria Australia.
¹⁴ Department of Chemistry and Biochemistry Old Dominion University Norfolk Virginia USA.

Abstract

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 ( ClyVSLS) 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 ClyVSLS 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 ClyVSLS 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.

Keywords: Montreal Protocol; VSLS; dichloromethane; ozone; phosgene; stratosphere.