Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Isotopic constraint on the twentieth-century increase in tropospheric ozone

Abstract

Tropospheric ozone (O3) is a key component of air pollution and an important anthropogenic greenhouse gas1. During the twentieth century, the proliferation of the internal combustion engine, rapid industrialization and land-use change led to a global-scale increase in O3 concentrations2,3; however, the magnitude of this increase is uncertain. Atmospheric chemistry models typically predict4,5,6,7 an increase in the tropospheric O3 burden of between 25 and 50 per cent since 1900, whereas direct measurements made in the late nineteenth century indicate that surface O3 mixing ratios increased by up to 300 per cent8,9,10 over that time period. However, the accuracy and diagnostic power of these measurements remains controversial2. Here we use a record of the clumped-isotope composition of molecular oxygen (18O18O in O2) trapped in polar firn and ice from 1590 to 2016 ad, as well as atmospheric chemistry model simulations, to constrain changes in tropospheric O3 concentrations. We find that during the second half of the twentieth century, the proportion of 18O18O in O2 decreased by 0.03 ± 0.02 parts per thousand (95 per cent confidence interval) below its 1590–1958 ad mean, which implies that tropospheric O3 increased by less than 40 per cent during that time. These results corroborate model predictions of global-scale increases in surface pollution and vegetative stress caused by increasing anthropogenic emissions of O3 precursors4,5,11. We also estimate that the radiative forcing of tropospheric O3 since 1850 ad is probably less than +0.4 watts per square metre, consistent with results from recent climate modelling studies12.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Mean atmospheric Δ36 values from different archives.
Fig. 2: Measurement–model comparisons for increase in tropospheric O3 since 1850 ad.
Fig. 3: Zonal-mean change in O3 concentrations between 1850 and 2005 ad.

Data availability

The isotopic data and main LOCK-IN firn data that support the findings of this study are available from the PANGAEA database (https://doi.pangaea.de/10.1594/PANGAEA.901154). The LOCK-IN firn analysis is ongoing, so additional firn data underlying sensitivity tests in Extended Data Fig. 6 will be published elsewhere and made available freely and immediately upon request.

Code availability

The computer codes used to support the findings of this study are available from the authors upon reasonable request.

References

  1. 1.

    National Research Council. Rethinking the Ozone Problem in Urban and Regional Air Pollution (National Academies Press, 1991).

  2. 2.

    Cooper, O. R. et al. Global distribution and trends of atmospheric ozone: an observation-based review. Elementa 2, 000029 (2014).

    Google Scholar 

  3. 3.

    Lamarque, J. F. et al. Historical (1850–2000) gridded anthropogenic and biomass burning emissions of reactive gases and aerosols: methodology and application. Atmos. Chem. Phys. 10, 7017–7039 (2010).

    CAS  ADS  Article  Google Scholar 

  4. 4.

    Murray, L. T. et al. Factors controlling variability in the oxidative capacity of the troposphere since the Last Glacial Maximum. Atmos. Chem. Phys. 14, 3589–3622 (2014).

    ADS  Article  Google Scholar 

  5. 5.

    Young, P. J. et al. Pre-industrial to end 21st century projections of tropospheric ozone from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). Atmos. Chem. Phys. 13, 2063–2090 (2013).

    ADS  Article  Google Scholar 

  6. 6.

    Parrella, J. P. et al. Tropospheric bromine chemistry: implications for present and pre-industrial ozone and mercury. Atmos. Chem. Phys. 12, 6723–6740 (2012).

    CAS  ADS  Article  Google Scholar 

  7. 7.

    Archibald, A. T. et al. Impacts of HOx regeneration and recycling in the oxidation of isoprene: Consequences for the composition of past, present, and future atmospheres. Geophys. Res. Lett. 38, L05804 (2011).

    ADS  Article  Google Scholar 

  8. 8.

    Volz, A. & Kley, D. Evaluation of the Montsouris series of ozone measurements made in the nineteenth century. Nature 332, 240–242 (1988).

    CAS  ADS  Article  Google Scholar 

  9. 9.

    Marenco, A., Gouget, H., Nédélec, P. & Pagés, J.-P. Evidence of a long-term increase in tropospheric ozone from Pic du Midi data series: consequences: positive radiative forcing. J. Geophys. Res. 99, 16617–16632 (1994).

    CAS  ADS  Article  Google Scholar 

  10. 10.

    Pavelin, E. G., Johnson, C. E., Rughoopth, S. & Toumi, R. Evaluation of pre-industrial surface ozone measurements made using Schönbein’s method. Atmos. Environ. 33, 919–929 (1999).

    CAS  ADS  Article  Google Scholar 

  11. 11.

    Worton, D. R. et al. Evidence from firn air for recent decreases in non-methane hydrocarbons and a 20th century increase in nitrogen oxides in the northern hemisphere. Atmos. Environ. 54, 592–602 (2012).

    CAS  ADS  Article  Google Scholar 

  12. 12.

    Checa-Garcia, R., Hegglin, M. I., Kinnison, D., Plummer, D. A. & Shine, K. P. Historical tropospheric and stratospheric ozone radiative forcing using the CMIP6 database. Geophys. Res. Lett. 45, 3264–3273 (2018).

    CAS  ADS  Article  Google Scholar 

  13. 13.

    Zhang, Y. et al. Tropospheric ozone change from 1980 to 2010 dominated by equatorward redistribution of emissions. Nat. Geosci. 9, 875–879 (2016).

    CAS  ADS  Article  Google Scholar 

  14. 14.

    Newland, M. J. et al. Changes to the chemical state of the Northern Hemisphere atmosphere during the second half of the twentieth century. Atmos. Chem. Phys. 17, 8269–8283 (2017).

    CAS  ADS  Article  Google Scholar 

  15. 15.

    Alexander, B. et al. Quantifying atmospheric nitrate formation pathways based on a global model of the oxygen isotope composition (Δ17O) of atmospheric nitrate. Atmos. Chem. Phys. 9, 5043–5056 (2009).

    CAS  ADS  Article  Google Scholar 

  16. 16.

    Erbland, J. et al. Air–snow transfer of nitrate on the East Antarctic Plateau – part 1: isotopic evidence for a photolytically driven dynamic equilibrium in summer. Atmos. Chem. Phys. 13, 6403–6419 (2013).

    ADS  Article  Google Scholar 

  17. 17.

    Yeung, L. Y., Ash, J. L. & Young, E. D. Rapid photochemical equilibration of isotope bond ordering in O2. J. Geophys. Res. 119, 10552–10566 (2014).

    CAS  Google Scholar 

  18. 18.

    Yeung, L. Y. et al. Isotopic ordering in atmospheric O2 as a tracer of ozone photochemistry and the tropical atmosphere. J. Geophys. Res. Atmos. 121, 12541–12559 (2016).

    CAS  ADS  Article  Google Scholar 

  19. 19.

    Taylor, K. C. et al. Dating the Siple Dome (Antarctica) ice core by manual and computer interpretation of annual layering. J. Glaciol. 50, 453–461 (2004).

    ADS  Article  Google Scholar 

  20. 20.

    Vinther, B. M. et al. A synchronized dating of three Greenland ice cores throughout the Holocene. J. Geophys. Res. Atmos. 111, (2006).

  21. 21.

    Buizert, C. et al. The WAIS Divide deep ice core WD2014 chronology – part 1: methane synchronization (68–31 ka BP) and the gas age–ice age difference. Clim. Past 11, 153–173 (2015).

    Article  Google Scholar 

  22. 22.

    Legrand, M. et al. Inter-annual variability of surface ozone at coastal (Dumont d’Urville, 2004–2014) and inland (Concordia, 2007–2014) sites in East Antarctica. Atmos. Chem. Phys. 16, 8053–8069 (2016).

    CAS  ADS  Article  Google Scholar 

  23. 23.

    Witrant, E. & Martinerie, P. Input estimation from sparse measurements in LPV systems and isotopic ratios in polar firns. IFAC Proc. 46, 659–664 (2013).

    Article  Google Scholar 

  24. 24.

    Witrant, E. et al. A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behaviour at eleven polar sites. Atmos. Chem. Phys. 12, 11465–11483 (2012).

    CAS  ADS  Article  Google Scholar 

  25. 25.

    Santer, B. D. et al. Human and natural influences on the changing thermal structure of the atmosphere. Proc. Natl Acad. Sci. USA 110, 17235–17240 (2013).

    CAS  ADS  Article  Google Scholar 

  26. 26.

    Boothe, A. C. & Homeyer, C. R. Global large-scale stratosphere–troposphere exchange in modern reanalyses. Atmos. Chem. Phys. 17, 5537–5559 (2017).

    CAS  ADS  Article  Google Scholar 

  27. 27.

    Butchart, N. et al. Chemistry–climate model simulations of twenty-first century stratospheric climate and circulation changes. J. Clim. 23, 5349–5374 (2010).

    ADS  Article  Google Scholar 

  28. 28.

    Lin, P. & Fu, Q. Changes in various branches of the Brewer–Dobson circulation from an ensemble of chemistry climate models. J. Geophys. Res. Atmos. 118, 73–84 (2013).

    CAS  ADS  Article  Google Scholar 

  29. 29.

    Gelaro, R. et al. The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). J. Clim. 30, 5419–5454 (2017).

    ADS  Article  Google Scholar 

  30. 30.

    Schmidt, G. A. et al. Configuration and assessment of the GISS ModelE2 contributions to the CMIP5 archive. J. Adv. Model. Earth Syst. 6, 141–184 (2014).

    ADS  Article  Google Scholar 

  31. 31.

    Sherwen, T., Evans, M. J., Carpenter, L. J., Schmidt, J. A. & Mickley, L. J. Halogen chemistry reduces tropospheric O3 radiative forcing. Atmos. Chem. Phys. 17, 1557–1569 (2017).

    CAS  ADS  Article  Google Scholar 

  32. 32.

    Legrand, M. et al. Alpine ice evidence of a three-fold increase in atmospheric iodine deposition since 1950 in Europe due to increasing oceanic emissions. Proc. Natl Acad. Sci. USA 115, 12136–12141 (2018).

    CAS  ADS  Article  Google Scholar 

  33. 33.

    Eiler, J. M. “Clumped-isotope” geochemistry—the study of naturally-occurring, multiply-substituted isotopologues. Earth Planet. Sci. Lett. 262, 309–327 (2007).

    CAS  ADS  Article  Google Scholar 

  34. 34.

    Eiler, J. M. & Schauble, E. 18O13C16O in the Earth’s atmosphere. Geochim. Cosmochim. Acta 68, 4767–4777 (2004).

    CAS  ADS  Article  Google Scholar 

  35. 35.

    Wang, Z., Schauble, E. A. & Eiler, J. M. Equilibrium thermodynamics of multiply substituted isotopologues of molecular gases. Geochim. Cosmochim. Acta 68, 4779–4797 (2004).

    CAS  ADS  Article  Google Scholar 

  36. 36.

    Yeung, L. Y., Hayles, J. A., Hu, H., Ash, J. L. & Sun, T. Scale distortion from pressure baselines as a source of inaccuracy in triple-isotope measurements. Rapid Commun. Mass Spectrom. 32:1811-1821 (2018).

    CAS  ADS  Article  Google Scholar 

  37. 37.

    Severinghaus, J. P., Grachev, A., Luz, B. & Caillon, N. A method for precise measurement of argon 40/36 and krypton/argon ratios in trapped air in polar ice with applications to past firn thickness and abrupt climate change in Greenland and at Siple Dome, Antarctica. Geochim. Cosmochim. Acta 67, 325–343 (2003).

    CAS  ADS  Article  Google Scholar 

  38. 38.

    Capron, E. et al. Synchronising EDML and NorthGRIP ice cores using δ18O of atmospheric oxygen (δ18Oatm) and CH4 measurements over MIS5 (80–123 kyr). Quat. Sci. Rev. 29, 222–234 (2010).

    ADS  Article  Google Scholar 

  39. 39.

    Schwander, J. et al. The age of the air in the firn and the ice at Summit, Greenland. J. Geophys. Res. Atmos. 98, 2831–2838 (1993).

    CAS  ADS  Article  Google Scholar 

  40. 40.

    Buizert, C. et al. Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland. Atmos. Chem. Phys. 12, 4259–4277 (2012); corrigendum 14, 3571–3572 (2014).

    CAS  ADS  Article  Google Scholar 

  41. 41.

    Fourteau, K. et al. Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions. Clim. Past 13, 1815–1830 (2017).

    Article  Google Scholar 

  42. 42.

    Huber, C. et al. Evidence for molecular size dependent gas fractionation in firn air derived from noble gases, oxygen, and nitrogen measurements. Earth Planet. Sci. Lett. 243, 61–73 (2006).

    CAS  ADS  Article  Google Scholar 

  43. 43.

    Severinghaus, J. P. & Battle, M. O. Fractionation of gases in polar ice during bubble close-off: new constraints from firn air Ne, Kr and Xe observations. Earth Planet. Sci. Lett. 244, 474–500 (2006).

    CAS  ADS  Article  Google Scholar 

  44. 44.

    Battle, M. O. et al. Controls on the movement and composition of firn air at the West Antarctic Ice Sheet Divide. Atmos. Chem. Phys. 11, 11007–11021 (2011); corrigendum 14, 9511 (2014).

    CAS  ADS  Article  Google Scholar 

  45. 45.

    Wang, Z. et al. The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget. Atmos. Chem. Phys. 12, 4365–4377 (2012).

    ADS  Article  Google Scholar 

  46. 46.

    Trudinger, C. M. et al. Modeling air movement and bubble trapping in firn. J. Geophys. Res. Atmos. 102, 6747–6763 (1997).

    CAS  ADS  Article  Google Scholar 

  47. 47.

    Burr, A. et al. Pore morphology of polar firn around closure revealed by X-ray tomography. Cryosphere 12, 2481–2500 (2018).

    ADS  Article  Google Scholar 

  48. 48.

    Yeung, L. Y., Young, E. D. & Schauble, E. A. Measurements of 18O18O and 17O18O in the atmosphere and the influence of isotope-exchange reactions. J. Geophys. Res. 117, D18306 (2012).

    ADS  Article  Google Scholar 

  49. 49.

    Butler, J. H. et al. A record of atmospheric halocarbons during the twentieth century from polar firn air. Nature 399, 749–755 (1999).

    CAS  ADS  Article  Google Scholar 

  50. 50.

    Kreutz, K. J., Mayewski, P. A., Whitlow, S. I. & Twickler, M. S. Limited migration of soluble ionic species in a Siple Dome, Antarctica, ice core. Ann. Glaciol. 27, 371–377 (1998).

    CAS  ADS  Article  Google Scholar 

  51. 51.

    Mitchell, L. E. et al. Observing and modeling the influence of layering on bubble trapping in polar firn. J. Geophys. Res. Atmos. 120, 2558–2574 (2015).

    ADS  Article  Google Scholar 

  52. 52.

    Ahn, J., Brook, E. J. & Buizert, C. Response of atmospheric CO2 to the abrupt cooling event 8200 years ago. Geophys. Res. Lett. 41, 604–609 (2014).

    CAS  ADS  Article  Google Scholar 

  53. 53.

    Rommelaere, V., Arnaud, L. & Barnola, J.-M. Reconstructing recent atmospheric trace gas concentrations from polar firn and bubbly ice data by inverse methods. J. Geophys. Res. Atmos. 102, 30069–30083 (1997).

    CAS  ADS  Article  Google Scholar 

  54. 54.

    Extier, T. et al. On the use of δ18Oatm for ice core dating. Quat. Sci. Rev. 185, 244–257 (2018).

    ADS  Article  Google Scholar 

  55. 55.

    Sapart, C. J. et al. Can the carbon isotopic composition of methane be reconstructed from multi-site firn air measurements? Atmos. Chem. Phys. 13, 6993–7005 (2013).

    ADS  Article  Google Scholar 

  56. 56.

    Eastham, S. D., Weisenstein, D. K. & Barrett, S. R. H. Development and evaluation of the unified tropospheric–stratospheric chemistry extension (UCX) for the global chemistry-transport model GEOS-Chem. Atmos. Environ. 89, 52–63 (2014).

    CAS  ADS  Article  Google Scholar 

  57. 57.

    Usoskin, I. G. & Kovaltsov, G. A. Production of cosmogenic 7Be isotope in the atmosphere: full 3-D modeling. J. Geophys. Res. Atmos. 113, D12107 (2008).

    ADS  Article  Google Scholar 

  58. 58.

    Yeung, L. Y., Ash, J. L. & Young, E. D. Biological signatures in clumped isotopes of O2. Science 348, 431–434 (2015).

    CAS  ADS  Article  Google Scholar 

  59. 59.

    Koch, D. M. & Rind, D. H. Beryllium 10/beryllium 7 as a tracer of stratospheric transport. J. Geophys. Res. 103, 3907–3917 (1998).

    ADS  Article  Google Scholar 

  60. 60.

    Field, C. V., Schmidt, G. A., Koch, D. M. & Salyk, C. Modeling production and climate-related impacts on 10Be concentration in ice cores. J. Geophys. Res. 111, D15107 (2006).

    ADS  Article  Google Scholar 

  61. 61.

    Usoskin, I. G. et al. Short-term production and synoptic influences on atmospheric 7Be concentrations. J. Geophys. Res. 114, D06108 (2009).

    ADS  Google Scholar 

  62. 62.

    Usoskin, I. G., Bazilevskaya, G. A. & Kovaltsov, G. A. Solar modulation parameter for cosmic rays since 1936 reconstructed from ground-based neutron monitors and ionization chambers. J. Geophys. Res. 116, A02104 (2011).

    ADS  Article  Google Scholar 

  63. 63.

    Clette, F. & Lefèvre, L. The new sunspot number: assembling all corrections. Sol. Phys. 291, 2629–2651 (2016).

    ADS  Article  Google Scholar 

  64. 64.

    Fraser-Smith, A. C. Centered and eccentric geomagnetic dipoles and their poles, 1600–1985. Rev. Geophys. 25, 1–16 (1987).

    ADS  Article  Google Scholar 

  65. 65.

    Hansen, J. et al. Climate impact of increasing atmospheric carbon dioxide. Science 213, 957–966 (1981).

    CAS  ADS  Article  Google Scholar 

  66. 66.

    Miller, R. L. et al. CMIP5 historical simulations (1850–2012) with GISS ModelE2. J. Adv. Model. Earth Syst. 6, 441–478 (2014).

    ADS  Article  Google Scholar 

  67. 67.

    The NCAR command language, version 6.6.2 (UCAR/NCAR/CISL/TDD, 2019); https://doi.org/10.5065/D6WD3XH5.

Download references

Acknowledgements

This work was supported by the David and Lucile Packard Foundation Science & Engineering Fellowship and by the European Commission’s Seventh Framework Programme ERC2011 under grant agreement number 291062 (ERC ICE&LASERS). We thank M. Twickler, G. Hargreaves and R. Nunn at the National Science Foundation Ice Core Facility for curating and providing ice-core samples for this study. We also thank X. Faïn, A. Lemoine and G. Teste for CO2 and CH4 laboratory measurements at IGE; G. P. Lee and W. Sturges and his team at the University of East Anglia for halocarbon measurements on the LOCK-IN canisters; J. Freitag and C. Florian Schaller at AWI and K. Fourteau at IGE for providing a high-resolution LOCK-IN density profile; E. Le Meur for evaluating the site elevation; K. Fourteau, C. F. Schaller and J. Savarino for discussions; and A. Landais for comments on the manuscript. The LOCK-IN field and scientific programme was funded by Institut Polaire Français Paul-Emile Victor programme number 1153 and Centre National de la Recherche Scientifique INSU/LEFE programme NEVE-CLIMAT. We thank the field personnel at the LOCK-IN site: D. Colin, P. Dordhain, P. Possenti, as well as P. Godon for setting up the field logistics.

Author information

Affiliations

Authors

Contributions

L.Y.Y., L.T.M. and J.C. designed the project. J.C., P.M. and A.O. collected the firn-air samples and analysed them for trace gases and bulk isotope ratios. L.Y.Y., H.H. and A.B. performed firn and ice-core clumped-isotope measurements. L.T.M. performed additional development of the GISS-E2.1 model and conducted the global model simulations, which were then analysed by L.Y.Y. P.M. and E.W. developed the atmospheric history inversions. L.Y.Y. wrote the paper with input from all authors.

Corresponding author

Correspondence to Laurence Y. Yeung.

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.

Extended data figures and tables

Extended Data Fig. 1 Age distribution estimates in firn and ice.

In green: gas age distributions in LOCK-IN firn at depths of 84.2 m (short-dashed line), 98.6 m (long-dashed line), 104.8 m depth (solid line) and 107.65 m (short–long dashed line). In red: gas age distribution of GISP2 ice samples. In blue: gas age distributions of WAIS Divide ice samples, estimated using a diffusivity based on NEEM-EU data (solid line) and NEEM-US data (dashed line). In purple: gas age distribution of Siple Dome ice samples.

Source Data

Extended Data Fig. 2 Comparison of the most precise model (in isotopic δ notation23) and the simplified model used to include ice data45.

Left, black stars show ∆36 (‘D-36’, in parts per thousand) data in LOCK-IN firn plotted against mean gas ages with uncertainties (±2 s.e.m., calculated using the pooled standard deviation) shown as vertical bars. Lines represent reconstructed atmospheric trends. The preferred scenario is obtained using a SCRIPPS-based O2 trend (see Methods, ‘Δ36 for firn modelling’) and is constrained by LOCK-IN firn data excluding the deepest value. The black and green solid lines show the best-guess trend obtained with the most precise and simplified models, respectively. Long-dashed lines show the uncertainty envelope. Short-dashed lines show the results of the two models when including the probably contaminated deepest data point (most precise model in green, simplified model in black). Right, δ18O18Ocor data (‘d18O18Ocor’, in parts per thousand; see Methods, ‘Δ36 for firn modelling’) in LOCK-IN firn against depth (symbols), compared with model results (lines). The four model simulations only differ in the very deep firn. The deepest data point at 107.65 m, which is probably contaminated (see text), is not shown in the left panel. Its mean gas age is 110 yr, corresponding to 1906 ad.

Source Data

Extended Data Fig. 3 Effect of gravitational fractionation on isotopic ratios in the LOCK-IN firn.

Shown are δ15N values of N2 measured at LSCE (black stars); δ18O values of O2, divided by 2, measured at LSCE (green crosses) and at Rice University (red circles); and δ18O18O values of O2, divided by 4, measured at Rice University (blue circles). The black line shows the barometric slope.

Source Data

Extended Data Fig. 4 Test of gravitational fractionation corrections for δ18O18O in LOCK-IN firn.

Shown are the corrections obtained using the δ15N value of N2 measured at LSCE (black stars), the δ18O value of O2 measured at LSCE (green crosses), the δ18O value of O2 measured at Rice University (red circles) and the ∆36 value of O2 measured at Rice University (empty blue circles).

Source Data

Extended Data Fig. 5 Comparison of firn model scenarios.

Shown are results obtained with or without the deepest LOCK-IN data point, and with constant or SCRIPPS-based O2 trend estimates, as well as forward firn model tests of atmospheric model scenarios. Top left, ∆36 data in firn and ice (LOCK-IN in green, GISP2 in red, WAIS Divide in blue, Siple Dome in purple) plotted against mean 18O18O age, compared with atmospheric trends obtained by inverse firn/ice modelling. Shown also are the ±2σ-equivalent uncertainty envelope for the inverse model (long-dashed black lines) and the best-guess trends obtained using: the SCRIPPS-based O2 scenario and excluding the deepest LOCK-IN data point (short-dashed black line); a constant-O2 scenario and excluding the deepest LOCK-IN data point (red line); the SCRIPPS-based O2 scenario and all LOCK-IN data points (dashed grey line); and a constant O2 scenario and all LOCK-IN data points (blue line). Top right, δ18O18Ocor in firn and ice (defined in Methods, ‘Δ36 for firn modelling’; LOCK-IN in green, GISP2 in red, WAIS Divide in blue, Siple Dome in purple) plotted against depth, compared with model results in firn and ice using the SCRIPPS-based O2 scenario. The solid lines show the simulation excluding the deepest LOCK-IN data point and the dashed lines correspond to the simulation with all data points. Bottom left, ∆36 data in firn and ice (same colours as in upper panels) compared with simulated profiles using the forward firn model (LOCK-IN, solid lines; WAIS Divide, long dashed lines; GISP2, short dashed lines; Siple Dome, short–long-dashed lines). Outputs shown correspond to SCRIPPS-based atmospheric concentration trends for O2 and constant values for δ18O and ∆36 (black lines); constant values for O2, δ18O and ∆36 (grey lines; results are nearly the same as the black lines); SCRIPPS-based atmospheric concentration trends for O2 and constant values for δ18O, with the +25% box model scenario for ∆36 (orange lines); the +200% box model scenario for ∆36 (blue lines); and the +300% box model scenario for ∆36 (red lines).

Source Data

Extended Data Fig. 6 Results of sensitivity tests on atmospheric trend reconstructions from the inverse firn model.

36 data in firn and ice (stars with ±2 s.e.m. uncertainties shown as vertical bars; LOCK-IN in green, GISP2 in red, WAIS Divide in blue, Siple Dome in purple) plotted against mean 18O18O age and compared with modelled atmospheric trends (lines). The solid black line is the preferred scenario, obtained using a SCRIPPS-based O2 concentration trend and excluding the deepest LOCK-IN data point, with its uncertainty envelope shown alongside (dashed black lines). The left panel shows the simulation that includes the deepest LOCK-IN data point (red line), a simulation with the deepest LOCK-IN data point corrected (grey star) from a maximum estimate of 10% surface air contamination (purple line), tests of the sensitivity to the optimal solution (grey lines; see Methods, ‘Sensitivity tests on atmospheric trend reconstructions’), the simulation excluding WAIS Divide data (blue line), and simulations excluding the Siple Dome data (green solid line) or excluding the Siple Dome data and using NEEM-US-data-based diffusivity to simulate WAIS Divide firn (green dashed line). The dashed grey line shows that a straight trend with a weak slope can remain in the uncertainty envelope. The right panel shows tests of LOCK-IN firn physics parameters (green; see Methods, ‘Sensitivity tests on atmospheric trend reconstructions’) and tests of LOCK-IN diffusivity constrained with field data only (blue), all nearly superimposed to the preferred trend.

Source Data

Extended Data Fig. 7 Comparison of Δ36 values in measurements of ice-core, firn and modern air.

a, Firn and ice-core Δ36 values (means of replicates) plotted against mean gas age. b, Kernel-smoothed probability density distributions of bootstrap-resampled mean values of each dataset, showing a significant (P < 0.002) difference between the means of the ice-core and firn (above 105 m) datasets. Uncertainties are omitted for clarity. Pooled standard deviations for each sample type are 0.03‰–0.04‰ (see Methods). C.E., common era.

Source Data

Extended Data Fig. 8 Modelled fraction of stratospheric air derived from GISS-E2.1 7Be simulations.

Shown are 12-month grid-scale moving averages at the surface near each of the four polar sampling sites between 1850 ad and 2015 ad.

Source Data

Extended Data Fig. 9 Instantaneous tropospheric O3 radiative forcing at the tropopause relative to 1850 ad.

Results calculated with the GISS-E2.1 (2000s) and GEOS-Chem/MERRA2 (2005) models. Maps created using the NCAR command language67.

Source Data

Extended Data Fig. 10 Solar modulation potential.

Results estimated using the sunspot number (orange line) and reconstructed from ground‐based neutron monitors and ionization chambers (from Usoskin et al.62; blue line).

Source Data

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Yeung, L.Y., Murray, L.T., Martinerie, P. et al. Isotopic constraint on the twentieth-century increase in tropospheric ozone. Nature 570, 224–227 (2019). https://doi.org/10.1038/s41586-019-1277-1

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links