Stratospheric ozone depletion, first observed in the 1980s, has been caused by the increased production and use of substances such as chlorofluorocarbons (CFCs), halons and other chlorine-containing and bromine-containing compounds, collectively termed ozone-depleting substances (ODSs). Following controls on the production of major, long-lived ODSs by the Montreal Protocol, the ozone layer is now showing initial signs of recovery and is anticipated to return to pre-depletion levels in the mid-to-late twenty-first century, likely 2050–2060. These return dates assume widespread compliance with the Montreal Protocol and, thereby, continued reductions in ODS emissions. However, recent observations reveal increasing emissions of some controlled (for example, CFC-11, as in eastern China) and uncontrolled substances (for example, very short-lived substances (VSLSs)). Indeed, the emissions of a number of uncontrolled VSLSs are adding significant amounts of ozone-depleting chlorine to the atmosphere. In this Review, we discuss recent emissions of both long-lived ODSs and halogenated VSLSs, and how these might lead to a delay in ozone recovery. Continued improvements in observational tools and modelling approaches are needed to assess these emerging challenges to a timely recovery of the ozone layer.
Ozone recovery is expected mid-century, owing to adherence to the Montreal Protocol, but a number of recent trends could challenge its timely recovery.
The apparent illicit production of CFC-11 is one such challenge to ozone recovery, but the added damage to the ozone layer in this case depends on how rapidly the CFC-11 emissions are mitigated.
A number of industrial processes that are allowed by the Montreal Protocol contribute considerable amounts of chlorinated gas emissions to the atmosphere.
Increases in ozone-depleting chlorine from a number of human-produced, short-lived gases have led to some increased ozone depletion, although their future impacts on ozone depend on future uses.
Natural processes also affect the balance of ozone in the stratosphere in a number of ways and could change in the future as climate responds to increases in atmospheric greenhouse gas concentrations.
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Bais, A. F. et al. Environmental effects of ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2017. Photochem. Photobiol. Sci. 17, 127–179 (2018).
Myhre, G. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 659–740 (Cambridge Univ. Press, 2013).
Thompson, D. W. J. & Solomon, S. Interpretation of recent Southern Hemisphere climate change. Science 296, 895–899 (2002).
Gillett, N. P. & Thompson, D. W. J. Simulation of recent Southern Hemisphere climate change. Science 302, 273–275 (2003).
Molina, M. J. & Rowland, F. S. Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone. Nature 249, 810–812 (1974).
Stolarski, R. S. & Cicerone, R. J. Stratospheric chlorine: a possible sink for ozone. Can. J. Chem. 52, 1610–1615 (1974).
Farman, J. C., Gardiner, B. G. & Shanklin, J. D. Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction. Nature 315, 207–210 (1985).
World Meteorological Organization. Scientific assessment of ozone depletion: 2018 (WMO, 2018).
Wofsy, S., McElroy, M. B. & Yung, Y. L. The chemistry of atmospheric bromine. Geophys. Res. Lett. 2, 215–218 (1975).
McElroy, M. B., Salawitch, R. J., Wofsy, S. C. & Logan, J. A. Reductions of Antarctic ozone due to synergistic interactions of chlorine and bromine. Nature 321, 759–762 (1986).
Montzka, S. A. et al. Decline in the tropospheric abundance of halogen from halocarbons: implications for stratospheric ozone depletion. Science 272, 1318–1322 (1996).
Prinn, R. G. et al. History of chemically and radiatively important atmospheric gases from the Advanced Global Atmospheric Gases Experiment (AGAGE). Earth Syst. Sci. Data 10, 985–1018 (2018).
Newchurch, M. J. et al. Evidence for slowdown in stratospheric ozone loss: first stage of ozone recovery. J. Geophys. Res. Atmos. 108, 4507 (2003).
Yang, E.-S. et al. First stage of Antarctic ozone recovery. J. Geophys. Res. Atmos. 113, D20308 (2008).
Solomon, S. et al. Emergence of healing in the Antarctic ozone layer. Science 353, 269–274 (2016).
Strahan, S. E., Douglass, A. R. & Damon, M. R. Why do Antarctic Ozone recovery trends vary? J. Geophys. Res. Atmos. 124, 8837–8850 (2019).
Chipperfield, M. P. et al. Detecting recovery of the stratospheric ozone layer. Nature 549, 211–218 (2017).
Eyring, V. et al. Multi-model assessment of stratospheric ozone return dates and ozone recovery in CCMVal-2 models. Atmos. Chem. Phys. 10, 9451–9472 (2010).
Oman, L. D. et al. Multimodel assessment of the factors driving stratospheric ozone evolution over the 21st century. J. Geophys. Res. Atmos. 115, D24306 (2010).
Dhomse, S. S. et al. Estimates of ozone return dates from chemistry-climate model initiative simulations. Atmos. Chem. Phys. 18, 8409–8438 (2018).
Montzka, S. A. et al. An unexpected and persistent increase in global emissions of ozone-depleting CFC-11. Nature 557, 413–417 (2018).
Rigby, M. et al. Increase in CFC-11 emissions from eastern China based on atmospheric observations. Nature 569, 546–550 (2019).
Schoenenberger, F. et al. First observations, trends, and emissions of HCFC-31 (CH2ClF) in the global atmosphere. Geophys. Res. Lett. 42, 7817–7824 (2015).
Vollmer, M. K. et al. Atmospheric histories and emissions of chlorofluorocarbons CFC-13 (CClF3), ΣCFC-114 (C2Cl2F4), and CFC-115 (C2ClF5). Atmos. Chem. Phys. 18, 979–1002 (2018).
Engel, A. et al. Scientific assessment of ozone depletion: 2018. Ch. 1 (WMO, 2018).
Laube, J. C. et al. Contribution of very short-lived organic substances to stratospheric chlorine and bromine in the tropics – a case study. Atmos. Chem. Phys. 8, 7325–7334 (2008).
Hossaini, R. et al. Recent trends in stratospheric chlorine from very short-lived substances. J. Geophys. Res. Atmos. 124, 2318–2335 (2019).
Brioude, J. et al. Variations in ozone depletion potentials of very short-lived substances with season and emission region. Geophys. Res. Lett. 37, L19804 (2010).
Pisso, I., Haynes, P. H. & Law, K. S. Emission location dependent ozone depletion potentials for very short-lived halogenated species. Atmos. Chem. Phys. 10, 12025–12036 (2010).
Claxton, T., Hossaini, R., Wild, O., Chipperfield, M. P. & Wilson, C. On the regional and seasonal ozone depletion potential of chlorinated very short-lived substances. Geophys. Res. Lett. 46, 5489–5498 (2019).
Technology and Economic Assessment Panel. Volume 1: decision XXX/3 TEAP task force report on unexpected emissions of trichlorofluoromethane (CFC-11) (TEAP, 2019).
Stratosphere-Troposphere Processes And Their Role In Climate. Lifetimes of stratospheric ozone-depleting substances, their replacements, and related species (WCRP, 2013).
Liang, Q. et al. Constraining the carbon tetrachloride (CCl4) budget using its global trend and inter-hemispheric gradient. Geophys. Res. Lett. 41, 5307–5315 (2014).
Harris, N. R. P. et al. Scientific assessment of ozone depletion: 2014. Ch. 5 (WMO, 2014).
Ashford, P., Clodic, D., McCulloch, A. & Kuijpers, L. Emission profiles from the foam and refrigeration sectors comparison with atmospheric concentrations. Part 1: methodology and data. Int. J. Refrig. 27, 687–700 (2004).
Laube, J. C. et al. Newly detected ozone-depleting substances in the atmosphere. Nat. Geosci. 7, 266–269 (2014).
Montzka, S. A., Butler, J. H., Hall, B. D., Mondeel, D. J. & Elkins, J. W. A decline in tropospheric organic bromine. Geophys. Res. Lett. 30, 1826 (2003).
Yvon-Lewis, S. A., Saltzman, E. S. & Montzka, S. A. Recent trends in atmospheric methyl bromide: analysis of post-Montreal Protocol variability. Atmos. Chem. Phys. 9, 5963–5974 (2009).
Butler, J. H. et al. A record of atmospheric halocarbons during the twentieth century from polar firn air. Nature 399, 749–755 (1999).
Trudinger, C. M. et al. Atmospheric histories of halocarbons from analysis of Antarctic firn air: methyl bromide, methyl chloride, chloroform, and dichloromethane. J. Geophys. Res. Atmos. 109, D22310 (2004).
Rhew, R. C., Miller, B. R., Vollmer, M. K. & Weiss, R. F. Shrubland fluxes of methyl bromide and methyl chloride. J. Geophys. Res. Atmos. 106, 20875–20882 (2001).
World Meteorological Organization. Scientific assessment of ozone depletion: 2010 (WMO, 2010).
Hossaini, R. et al. Growth in stratospheric chlorine from short-lived chemicals not controlled by the Montreal Protocol. Geophys. Res. Lett. 42, 4573–4580 (2015).
Hossaini, R. et al. The increasing threat to stratospheric ozone from dichloromethane. Nat. Commun. 8, 15962 (2017).
Fang, X. et al. Rapid increase in ozone-depleting chloroform emissions from China. Nat. Geosci. 12, 89–93 (2019).
Feng, Y., Bie, P., Wang, Z., Wang, L. & Zhang, J. Bottom-up anthropogenic dichloromethane emission estimates from China for the period 2005–2016 and predictions of future emissions. Atmos. Environ. 186, 241–247 (2018).
Schlosser, P. M., Bale, A. S., Gibbons, C. F., Wilkins, A. & Cooper, G. S. Human health effects of dichloromethane: key findings and scientific issues. Environ. Health Perspect. 123, 114–119 (2015).
Fang, X. et al. Challenges for the recovery of the ozone layer. Nat. Geosci. 12, 592–596 (2019).
McCulloch, A. Chloroform in the environment: occurrence, sources, sinks and effects. Chemosphere 50, 1291–1308 (2003).
Simmonds, P. G., Derwent, R. G., Manning, A. J., O’Doherty, S. & Spain, G. Natural chloroform emissions from the blanket peat bogs in the vicinity of Mace Head, Ireland over a 14-year period. Atmos. Environ. 44, 1284–1291 (2010).
Kahlil, M. A. K. et al. Natural emissions of chlorine-containing gases: reactive chlorine emissions inventory. J. Geophys. Res. Atmos. 104, 8333–8346 (1999).
Ooki, A. & Yokouchi, Y. Dichloromethane in the Indian Ocean: evidence for in-situ production in seawater. Mar. Chem. 124, 119–124 (2011).
Worton, D. R. et al. 20th century trends and budget implications of chloroform and related tri-and dihalomethanes inferred from firn air. Atmos. Chem. Phys. 6, 2847–2863 (2006).
Simmonds, P. G. et al. Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania. J. Geophys. Res. Atmos. 111, D18304 (2006).
Kim, I., Ha, J., Lee, J. H., Yoo, K.-m. & Rho, J. The relationship between the occupational exposure of trichloroethylene and kidney cancer. Ann. Occup. Environ. Med. 26, 12 (2014).
Friesen, M. C. et al. Historical occupational trichloroethylene air concentrations based on inspection measurements from Shanghai, China. Ann. Occup. Hyg. 59, 62–78 (2015).
Leedham Elvidge, E. et al. Increasing concentrations of dichloromethane, CH2Cl2, inferred from CARIBIC air samples collected 1998–2012. Atmos. Chem. Phys. 15, 1939–1958 (2015).
Harrison, J. J., Chipperfield, M. P., Hossaini, R. & Boone, C. D. Phosgene in the upper troposphere and lower stratosphere: a marker for product gas injection due to chlorine-containing very short lived substances. Geophys. Res. Lett. 46, 1032–1039 (2019).
Rinsland, C. P. et al. Long-term trends of inorganic chlorine from ground-based infrared solar spectra: past increases and evidence for stabilization. J. Geophys. Res. Atmos. 108, D4252 (2003).
Froidevaux, L. et al. Global OZone Chemistry And Related trace gas Data records for the Stratosphere (GOZCARDS): methodology and sample results with a focus on HCl, H2O, and O3. Atmos. Chem. Phys. 15, 10471–10507 (2015).
Bernath, P. & Fernando, A. M. Trends in stratospheric HCl from the ACE satellite mission. J. Quant. Spectrosc. Radiat. Transf. 217, 126–129 (2018).
Froidevaux, L., Kinnison, D. E., Wang, R., Anderson, J. & Fuller, R. A. Evaluation of CESM1 (WACCM) free-running and specified dynamics atmospheric composition simulations using global multispecies satellite data records. Atmos. Chem. Phys. 19, 4783–4821 (2019).
Dorf, M. et al. Balloon-borne stratospheric BrO measurements: comparison with Envisat/SCIAMACHY BrO limb profiles. Atmos. Chem. Phys. 6, 2483–2501 (2006).
Quack, B. & Wallace, D. W. R. Air-sea flux of bromoform: controls, rates, and implications. Global Biogeochem. Cycles 17, 1023 (2003).
Butler, J. H. et al. Oceanic distributions and emissions of short-lived halocarbons. Global Biogeochem. Cycles 21, GB1023 (2007).
Gschwend, P. M., MacFarlane, J. K. & Newman, K. A. Volatile halogenated organic compounds released to seawater from temperate marine macroalgae. Science 227, 1033–1035 (1985).
Carpenter, L. J. & Liss, P. S. On temperate sources of bromoform and other reactive organic bromine gases. J. Geophys. Res. Atmos. 105, 20539–20547 (2000).
von Glasow, R. Sun, sea and ozone destruction. Nature 453, 1195–1196 (2008).
Tegtmeier, S. et al. Oceanic bromoform emissions weighted by their ozone depletion potential. Atmos. Chem. Phys. 15, 13647–13663 (2015).
Fuhlbrügge, S. et al. The contribution of oceanic halocarbons to marine and free troposphere air over the tropical West Pacific. Atmos. Chem. Phys. 16, 7569–7585 (2016).
Fiehn, A. et al. Delivery of halogenated very short-lived substances from the West Indian Ocean to the stratosphere during Asian summer monsoon. Atmos. Chem. Phys. 17, 6723–6741 (2017).
Aschmann, J., Sinnhuber, B.-M., Chipperfield, M. P. & Hossaini, R. Impact of deep convection and dehydration on bromine loading in the upper troposphere and lower stratosphere. Atmos. Chem. Phys. 11, 2671–2687 (2011).
Hossaini, R. et al. Modelling future changes to the stratospheric source gas injection of biogenic bromocarbons. Geophys. Res. Lett. 39, L20813 (2012).
Fiehn, A., Quack, B., Stemmler, I., Ziska, F. & Krüger, K. Importance of seasonally resolved oceanic emissions for bromoform delivery from the tropical Indian Ocean and west Pacific to the stratosphere. Atmos. Chem. Phys. 18, 11973–11990 (2018).
Ziska, F. et al. Global sea-to-air flux climatology for bromoform, dibromomethane and methyl iodide. Atmos. Chem. Phys. 13, 8915–8934 (2013).
Wales, P. A. et al. Stratospheric injection of brominated very short-lived substances: aircraft observations in the Western Pacific and representation in global models. J. Geophys. Res. Atmos. 123, 5690–5719 (2018).
Sherry, D., McCulloch, A., Liang, Q., Reimann, S. & Newman, P. A. Current sources of carbon tetrachloride (CCl4) in our atmosphere. Environ. Res. Lett. 13, 024004 (2018).
Delacroix, S., Vogelsang, C., Tobiesen, A. & Liltved, H. Disinfection by-products and ecotoxicity of ballast water after oxidative treatment - results and experiences from seven years of full-scale testing of ballast water management systems. Mar. Pollut. Bull. 73, 24–36 (2013).
Liu, Z. et al. Removing of disinfection by-product precursors from surface water by using magnetic graphene oxide. PLoS One 10, e0143819 (2015).
Maas, J. et al. Simulating the spread of disinfection by-products and anthropogenic bromoform emissions from ballast water discharge in Southeast Asia. Ocean Sci. 15, 891–904 (2019).
Yang, J. S. Bromoform in the effluents of a nuclear power plant: a potential tracer of coastal water masses. Hydrobiologia 464, 99–105 (2001).
Boudjellaba, D., Dron, J., Revenko, G., Démelas, C. & Boudenne, J. L. Chlorination by-product concentration levels in seawater and fish of an industrialised bay (Gulf of Fos, France) exposed to multiple chlorinated effluents. Sci. Total Environ. 541, 391–399 (2016).
Maas, J. et al. Simulations of anthropogenic bromoform indicate high emissions at the coast of East Asia. Atmos. Chem. Phys. Discuss. https://doi.org/10.5194/acp-2019-1004 (2020).
Leedham, E. C. et al. Emission of atmospherically significant halocarbons by naturally occurring and farmed tropical macroalgae. Biogeosciences 10, 3615–3633 (2013).
Dhomse, S. S. et al. Delay in recovery of the Antarctic ozone hole from unexpected CFC-11 emissions. Nat. Commun. 10, 5781 (2019).
Dameris, M., Jöckel, P. & Nützel, M. Possible implications of enhanced chlorofluorocarbon-11 concentrations on ozone. Atmos. Chem. Phys. 19, 13759–13771 (2019).
Fleming, E. L., Newman, P. A., Liang, Q. & Daniel, J. S. The impact of continuing CFC-11 emissions on stratospheric ozone. J. Geophys. Res. Atmos. 125, e2019JD031849 (2020).
Stratosphere-Troposphere Processes And Their Role In Climate. The mystery of carbon tetrachloride (WCRP, 2016).
Nolan Sherry and Associates & Tecnon Orbichem. Carbon tetrachloride 2016–2025: long, balanced or tightening? The impact of HFOs. NSA http://www.nolansherry.com/assets/hfos_is_there_enough_feedstock.pdf (2016).
Falk, S. et al. Brominated VSLS and their influence on ozone under a changing climate. Atmos. Chem. Phys. 17, 11313–11329 (2017).
Ziska, F., Quack, B., Tegtmeier, S., Stemmler, I. & Krüger, K. Future emissions of marine halogenated very-short lived substances under climate change. J. Atmos. Chem. 74, 245–260 (2017).
Dessens, O., Zeng, G., Warwick, N. & Pyle, J. Short-lived bromine compounds in the lower stratosphere; impact of climate change on ozone. Atmos. Sci. Lett. 10, 201–206 (2009).
Reimann, S. et al. Observing the atmospheric evolution of ozone-depleting substances. Comptes Rendus Geosci. 350, 384–392 (2018).
Carpenter, L. J. et al. Scientific assessment of ozone depletion: 2018. Ch. 6 (WMO, 2018).
Chipperfield, M. P. New version of the TOMCAT/SLIMCAT off-line chemical transport model: intercomparison of stratospheric tracer experiments. Q. J. R. Meteorol. Soc. 132, 1179–1203 (2006).
World Meteorological Organization. Scientific assessment of ozone depletion: 2014 (WMO, 2014).
Mahieu, E. et al. Recent Northern Hemisphere stratospheric HCl increase due to atmospheric circulation changes. Nature 515, 104–107 (2014).
Chipperfield, M. P. et al. On the cause of recent variations in lower stratospheric ozone. Geophys. Res. Lett. 45, 5718–5726 (2018).
Chipperfield, M. P. et al. Quantifying the ozone and ultraviolet benefits already achieved by the Montreal Protocol. Nat. Commun. 6, 7233 (2015).
The authors thank S. Dhomse (University of Leeds) for the data provided in Fig. 6. M.P.C. and R.H. acknowledge support through the Natural Environment Research Council (NERC) Sources and Impacts of Short-Lived Anthropogenic Chlorine (SISLAC) grant NE/R001782/1. R.H. is supported by a NERC Independent Research Fellowship (NE/N014375/1).
The authors declare no competing interests.
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Advanced Global Atmospheric Gases Experiment (AGAGE) monitoring network: https://agage.mit.edu/
National Aeronautics and Space Administration Ozone Watch: https://ozonewatch.gsfc.nasa.gov/
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United Nations Environment Programme: https://www.unenvironment.org/
United Nations Environment Programme Ozone Country Data: https://ozone.unep.org/countries/data-table
World Meteorological Organization and United Nations Environment Programme Ozone Assessments: https://www.esrl.noaa.gov/csd/assessments/ozone/
Layer of atmosphere (approximately 15–50 km).
Layer of atmosphere (surface to approximately 15 km).
- Ozone-depleting substances
(ODSs). Man-made chlorine- and bromine-containing gases that cause ozone depletion once they reach the stratosphere and are controlled by the Montreal Protocol.
Ozone-depleting substance included in the Montreal Protocol for limits on consumption and production.
Reservoirs of produced ozone-depleting substances stored in equipment or materials and not yet released to the atmosphere.
Application that does not lead to the eventual emission of ozone-depleting substances.
A halogenated chemical whose production and/or international trade is not controlled by the Montreal Protocol.
- Very short-lived substances
(VSLSs). Substances with an atmospheric lifetime of less than half a year.
- Ozone-depletion potentials
Relative amounts of ozone loss caused by the emission of 1 kg of a substance compared with the emission of 1 kg of CFC-11.
Measure of the removal rate (e-folding time) of emitted species by atmospheric processes.
Reaction of a feedstock with a fluorine-containing compound to produce a substance.
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Chipperfield, M.P., Hossaini, R., Montzka, S.A. et al. Renewed and emerging concerns over the production and emission of ozone-depleting substances. Nat Rev Earth Environ 1, 251–263 (2020). https://doi.org/10.1038/s43017-020-0048-8
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