Large climate-induced changes in ultraviolet index and stratosphere-to-troposphere ozone flux


Now that stratospheric ozone depletion has been controlled by the Montreal Protocol1, interest has turned to the effects of climate change on the ozone layer2,3. Climate models predict an accelerated stratospheric circulation4,5,6, leading to changes in the spatial distribution of stratospheric ozone2,7 and an increased stratosphere-to-troposphere ozone flux8,9. Here we use an atmospheric chemistry climate model to isolate the effects of climate change from those of ozone depletion and recovery on stratosphere-to-troposphere ozone flux and the clear-sky ultraviolet radiation index—a measure of potential human exposure to ultraviolet radiation. We show that under the Intergovernmental Panel on Climate Change moderate emissions scenario10, global stratosphere-to-troposphere ozone flux increases by 23% between 1965 and 2095 as a result of climate change. During this time, the clear-sky ultraviolet radiation index decreases by 9% in northern high latitudes—a much larger effect than that of stratospheric ozone recovery—and increases by 4% in the tropics, and by up to 20% in southern high latitudes in late spring and early summer. The latter increase in the ultraviolet index is equivalent to nearly half of that generated by the Antarctic ‘ozone hole’ that was created by anthropogenic halogens. Our results suggest that climate change will alter the tropospheric ozone budget and the ultraviolet index, which would have consequences for tropospheric radiative forcing11, air quality8 and human and ecosystem health12.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Predicted changes in the residual vertical velocity and ozone.
Figure 2: Predicted changes in STE ozone flux.
Figure 3: Predicted changes in ultraviolet index.


  1. 1

    World Meteorological Organization. Scientific Assessment of Ozone Depletion: 2006, WMO/U.N. Environ. Prog. Rep. 50 (WMO, 2007).

  2. 2

    Shepherd, T. G. Dynamics, stratospheric ozone, and climate change. Atmos. Ocean 46, 117–138 (2008).

  3. 3

    Waugh, D. W. et al. Impacts of climate change on stratospheric ozone recovery. Geophys. Res. Lett. 36, L03805 (2009).

  4. 4

    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).

  5. 5

    Butchart, N. et al. Simulations of anthropogenic change in the strength of the Brewer–Dobson circulation. Clim. Dyn. 27, 727–741 (2006).

  6. 6

    McLandress, C. & Shepherd, T. G. Simulated anthropogenic changes in the Brewer–Dobson circulation, including its extension to high latitudes. J. Clim. 22, 1516–1540 (2009).

  7. 7

    Li, F., Stolarski, R. S. & Newman, P. A. Stratospheric ozone in the post-CFC era. Atmos. Chem. Phys. 9, 2207–2213 (2009).

  8. 8

    Stevenson, D. S. et al. Multimodel ensemble simulations of present-day and near-future tropospheric ozone. J. Geophys. Res. 111, D8301 (2006).

  9. 9

    Denman, K. L. et al. in IPCC Climate Change 2007: The Physical Science Basis (eds Solomon, S. et al.) (Cambridge Univ. Press, 2007).

  10. 10

    Intergovernmental Panel on Climate Change. Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, 2000).

  11. 11

    Forster, P. & Shine, K. Radiative forcing and temperature trends from stratospheric ozone changes. J. Geophys. Res. 102, 10841–10855 (1997).

  12. 12

    United Nations Environment Program. Environmental Effects of Ozone Depletion and its Interactions with Climate Change: 2006 Assessment ISBN: 978-92-807-2821-7 (UNEP, 2006).

  13. 13

    Waugh, D. W. The age of stratospheric air. Nature Geosci. 2, 14–16 (2009).

  14. 14

    Engel, A. et al. Age of stratospheric air unchanged within uncertainties over the past 30 years. Nature Geosci. 2, 28–31 (2009).

  15. 15

    Austin, J. et al. Uncertainties and assessments of chemistry-climate models of the stratosphere. Atmos. Chem. Phys. 3, 1–27 (2003).

  16. 16

    Eyring, V. et al. Multimodel projections of stratospheric ozone in the 21st century. J. Geophys. Res. 112, D16303 (2007).

  17. 17

    de Grandpré, J. et al. Ozone climatology using interactive chemistry: Results from the Canadian middle atmosphere model. J. Geophys. Res. 105, 26475–26491 (2000).

  18. 18

    Scinocca, J., McFarlane, N. A., Lazare, M., Li, J. & Plummer, D. Technical Note: The CCCma third generation AGCM and its extension into the middle atmosphere. Atmos. Chem. Phys. 8, 7055–7074 (2008).

  19. 19

    Eyring, V. et al. Assessment of temperature, trace species, and ozone in chemistry-climate model simulations of the recent past. J. Geophys. Res. 111, D22308 (2006).

  20. 20

    Waugh, D. W. & Eyring, V. Quantitative performance metrics for stratospheric-resolving chemistry-climate models. Atmos. Chem. Phys. 8, 5699–5713 (2008).

  21. 21

    Andrews, D. G., Holton, J. R. & Leovy, C. B. Middle Atmosphere Dynamics (Academic, 1987).

  22. 22

    Shepherd, T. G. Transport in the middle atmosphere. J. Meteorol. Soc. Japan 85B, 165–191 (2007).

  23. 23

    Jonsson, A. I., de Grandpré, J., Fomichev, V. I., McConnell, J. C. & Beagley, S. R. Doubled CO2-induced cooling in the middle atmosphere: Photochemical analysis of the ozone radiative feedback. J. Geophys. Res. 109, D24103 (2004).

  24. 24

    Hsu, J., Prather, M. J. & Wild, O. Diagnosing the stratosphere-to-troposphere flux of ozone in a chemistry transport model. J. Geophys. Res. 110, D19305 (2005).

  25. 25

    Madronich, S. Analytic formula for the clear-sky UV index. Photochem. Photobiol. 83, 1537–1538 (2007).

  26. 26

    Tourpali, K. et al. Clear sky UV simulations in the 21st century based on ozone and temperature projections from chemistry-climate models. Atmos. Chem. Phys. 9, 1165–1172 (2009).

  27. 27

    Randall, D. A. et al. in IPCC Climate Change 2007: The Physical Science Basis (eds Solomon, S. et al.) (Cambridge Univ. Press, 2007).

  28. 28

    World Meteorological Organization. Scientific Assessment of Ozone Depletion: 2002, Global Ozone Research and Monitoring Project Rep. 47 (WMO, 2003).

  29. 29

    Appenzeller, C., Holton, J. & Rosenlof, K. Seasonal variation of mass transport across the tropopause. J. Geophys. Res. 101, 15071–15078 (1996).

  30. 30

    Olsen, M. A., Schoeberl, M. R. & Douglass, A. R. Stratosphere–troposphere exchange of mass and ozone. J. Geophys. Res. 109, D24114 (2004).

Download references


The authors would like to acknowledge helpful discussions with V. Fioletov on ultraviolet index and C. McLandress on STE ozone fluxes. This study has been financially supported by the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS) through the C-SPARC project, which provided the CMAM simulations.

Author information

M.I.H. initiated the project and analysed the model data. T.G.S. helped in the data interpretation and with the writing of the manuscript.

Correspondence to Michaela I. Hegglin.

Supplementary information

Supplementary Information

Supplementary Information (PDF 215 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

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

Download citation

Further reading