Challenges for the recovery of the ozone layer


The recovery of stratospheric ozone from past depletion is underway owing to the 1987 Montreal Protocol and its subsequent amendments, which have been effective in phasing out the production and consumption of the major ozone-depleting substances (ODSs). However, there is uncertainty about the future rate of recovery. This uncertainty relates partly to unexpected emissions of controlled anthropogenic ODSs such as CCl3F and slower-than-expected declines in atmospheric CCl4. A further uncertainty surrounds emissions of uncontrolled short-lived anthropogenic ODSs (such as CH2Cl2 and CHCl3), which observations show have been increasing in the atmosphere through 2017, as well as potential emission increases in natural ODSs (such as CH3Cl and CH3Br) induced by climate change, changes in atmospheric concentrations of greenhouse gases N2O and CH4, and stratospheric geoengineering. These challenges could delay the return of stratospheric ozone levels to historical values, (for example, the abundance in 1980), by up to decades, depending on the future evolution of the emissions and other influencing factors. To mitigate the threats to future ozone recovery, it is crucial to ensure that the Montreal Protocol and its amendments continue to be implemented effectively in order to have firm control on future levels of ODSs. This action needs to be supported by an expansion of the geographic coverage of atmospheric observations of ODSs, by enhancing the ability of source attribution modelling, and by improving understanding of the interactions between climate change and ozone recovery.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Amendments to the Montreal Protocol and ODS emissions during the period 1980–2016.
Fig. 2: Schematic of ozone recovery.
Fig. 3: Schematic of potential challenges for ozone recovery.
Fig. 4: Growth of global mean atmospheric abundances of N2O, CH2Cl2 and CHCl3 from 2004 to 2017.


  1. 1.

    Molina, M. J. & Rowland, F. S. Stratospheric sink for chlorofluoromethanes: chlorine atomic-catalysed destruction of ozone. Nature 249, 810–812 (1974).

    Article  Google Scholar 

  2. 2.

    Handbook for the Montreal Protocol on Substances that Deplete the Ozone Layer 12th edn (UNEP, 2018);

  3. 3.

    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).

    Article  Google Scholar 

  4. 4.

    Engel, A. et al. Scientific Assessment of Ozone Depletion: 2018 Report No. 58, Ch. 1 (Global Ozone Research and Monitoring Project, WMO, 2018).

  5. 5.

    Kuttippurath, J., Kumar, P., Nair, P. J. & Pandey, P. C. Emergence of ozone recovery evidenced by reduction in the occurrence of Antarctic ozone loss saturation. npj Clim. Atmos. Sci. 1, 42 (2018).

    Article  Google Scholar 

  6. 6.

    Solomon, S. et al. Emergence of healing in the Antarctic ozone layer. Science 353, 269–274 (2016).

    Article  Google Scholar 

  7. 7.

    Shepherd, T. G. et al. Reconciliation of halogen-induced ozone loss with the total-column ozone record. Nat. Geosci. 7, 443–449 (2014).

    Article  Google Scholar 

  8. 8.

    Scientific Assessment of Ozone Depletion: 2018 Report No. 58 (Global Ozone Research and Monitoring Project, WMO, 2018).

  9. 9.

    Montzka, S. A. et al. An unexpected and persistent increase in global emissions of ozone-depleting CFC-11. Nature 557, 413–417 (2018).

    Article  Google Scholar 

  10. 10.

    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).

    Article  Google Scholar 

  11. 11.

    Laube, J. C. et al. Newly detected ozone-depleting substances in the atmosphere. Nat. Geosci. 7, 266–269 (2014).

    Article  Google Scholar 

  12. 12.

    Hossaini, R. et al. The increasing threat to stratospheric ozone from dichloromethane. Nat. Commun. 8, 15962 (2017).

    Article  Google Scholar 

  13. 13.

    Fang, X. et al. Rapid increase in ozone-depleting chloroform emissions from China. Nat. Geosci. 12, 89–93 (2019).

    Article  Google Scholar 

  14. 14.

    Chipperfield, M. P. et al. Detecting recovery of the stratospheric ozone layer. Nature 549, 211–218 (2017).

    Article  Google Scholar 

  15. 15.

    Dhomse, S. S. et al. Estimates of ozone return dates from Chemistry-Climate Model Initiative simulations. Atmos. Chem. Phys. 18, 8409–8438 (2018).

    Article  Google Scholar 

  16. 16.

    Rigby, M. et al. Increase in CFC-11 emissions from eastern China based on atmospheric observations. Nature 569, 546–550 (2019).

    Article  Google Scholar 

  17. 17.

    Carpenter, L. J. et al. Scientific Assessment of Ozone Depletion: 2018 Report No. 58, Ch. 6 (Global Ozone Research and Monitoring Project, WMO, 2018).

  18. 18.

    Scientific Assessment of Ozone Depletion: 2014 Report No. 55 (Global Ozone Research and Monitoring Project, WMO, 2014);

  19. 19.

    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).

    Article  Google Scholar 

  20. 20.

    Lunt, M. F. et al. Continued emissions of the ozone-depleting substance carbon tetrachloride from Eastern Asia. Geophys. Res. Lett. 45, 11423–11430 (2018).

    Article  Google Scholar 

  21. 21.

    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).

    Article  Google Scholar 

  22. 22.

    Thompson, D. W. J. et al. Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change. Nat. Geosci. 4, 741–749 (2011).

    Article  Google Scholar 

  23. 23.

    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).

    Article  Google Scholar 

  24. 24.

    Hegglin, M. I. & Shepherd, T. G. Large climate-induced changes in ultraviolet index and stratosphere-to-troposphere ozone flux. Nat. Geosci. 2, 687–691 (2009).

    Article  Google Scholar 

  25. 25.

    Butchart, N. & Scaife, A. A. Removal of chlorofluorocarbons by increased mass exchange between the stratosphere and troposphere in a changing climate. Nature 410, 799–802 (2001).

    Article  Google Scholar 

  26. 26.

    Williams, M. B., Aydin, M., Tatum, C. & Saltzman, E. S. A 2000 year atmospheric history of methyl chloride from a South Pole ice core: evidence for climate-controlled variability. Geophys. Res. Lett. 34, L07811 (2007).

    Google Scholar 

  27. 27.

    Pilinis, C., King, D. B. & Saltzman, E. S. The oceans: a source or a sink of methyl bromide? Geophys. Res. Lett. 23, 817–820 (1996).

    Article  Google Scholar 

  28. 28.

    Tegtmeier, S. et al. Oceanic bromoform emissions weighted by their ozone depletion potential. Atmos. Chem. Phys. 15, 13647–13663 (2015).

    Article  Google Scholar 

  29. 29.

    Liang, Q., Strahan, S. E. & Fleming, E. L. Concerns for ozone recovery. Science 358, 1257–1258 (2017).

    Article  Google Scholar 

  30. 30.

    Global Mitigation of Non-CO 2 Greenhouse Gases: 2010–2030 (EPA, 2013);

  31. 31.

    Ravishankara, A. R., Daniel, J. S. & Portmann, R. W. Nitrous oxide (N2O): the dominant ozone-depleting substance emitted in the 21st century. Science 326, 123–125 (2009).

    Article  Google Scholar 

  32. 32.

    Kanter, D. et al. A post-Kyoto partner: considering the stratospheric ozone regime as a tool to manage nitrous oxide. Proc. Natl Acad. Sci. USA 110, 4451–4457 (2013).

    Article  Google Scholar 

  33. 33.

    Meinshausen, M. et al. The RCP greenhouse gas concentrations and their extensions from 1765 to 2300. Clim. Change 109, 213–241 (2011).

    Article  Google Scholar 

  34. 34.

    Rasch, P. J. et al. An overview of geoengineering of climate using stratospheric sulphate aerosols. Philos. Trans. R. Soc. Lond. A 366, 4007–4037 (2008).

    Article  Google Scholar 

  35. 35.

    Tilmes, S., Muller, R. & Salawitch, R. The sensitivity of polar ozone depletion to proposed geoengineering schemes. Science 320, 1201–1204 (2008).

    Article  Google Scholar 

  36. 36.

    Keith, D. W., Weisenstein, D. K., Dykema, J. A. & Keutsch, F. N. Stratospheric solar geoengineering without ozone loss. Proc. Natl Acad. Sci. USA 113, 14910–14914 (2016).

    Article  Google Scholar 

Download references


X.F. and R.G.P. were supported by NASA grant numbers NAG5-12669, NNX07AE89G, NNX11AF17G and NNX16AC98G to MIT. S.P. was supported by the National Strategic Project-Fine particle of the NRF funded by the MSIT, ME and MOHW (grant no. NRF-2017M3D8A1092225). We thank the station personnel at AGAGE stations for continuously measuring atmospheric N2O, CH2Cl2, CHCl3 and other referenced species, and R. H. Wang at the Georgia Institute of Technology for producing global monthly mean data of these species from the measurements from individual AGAGE stations. We thank Z. Dai from Harvard University for useful discussions on stratospheric geoengineering.

Author information




X.F. and R.G.P. were responsible for the overall project design. All authors wrote the manuscript.

Corresponding author

Correspondence to Xuekun Fang.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Fang, X., Pyle, J.A., Chipperfield, M.P. et al. Challenges for the recovery of the ozone layer. Nat. Geosci. 12, 592–596 (2019).

Download citation

Further reading


Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing