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The Montreal Protocol protects the terrestrial carbon sink

Abstract

The control of the production of ozone-depleting substances through the Montreal Protocol means that the stratospheric ozone layer is recovering1 and that consequent increases in harmful surface ultraviolet radiation are being avoided2,3. The Montreal Protocol has co-benefits for climate change mitigation, because ozone-depleting substances are potent greenhouse gases4,5,6,7. The avoided ultraviolet radiation and climate change also have co-benefits for plants and their capacity to store carbon through photosynthesis8, but this has not previously been investigated. Here, using a modelling framework that couples ozone depletion, climate change, damage to plants by ultraviolet radiation and the carbon cycle, we explore the benefits of avoided increases in ultraviolet radiation and changes in climate on the terrestrial biosphere and its capacity as a carbon sink. Considering a range of strengths for the effect of ultraviolet radiation on plant growth8,9,10,11,12, we estimate that there could have been 325–690 billion tonnes less carbon held in plants and soils by the end of this century (2080–2099) without the Montreal Protocol (as compared to climate projections with controls on ozone-depleting substances). This change could have resulted in an additional 115–235 parts per million of atmospheric carbon dioxide, which might have led to additional warming of global-mean surface temperature by 0.50–1.0 degrees. Our findings suggest that the Montreal Protocol may also be helping to mitigate climate change through avoided decreases in the land carbon sink.

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Fig. 1: The ozone, climate and biologically active UV levels of different futures.
Fig. 2: Effects on the productivity and stores of the terrestrial carbon cycle.
Fig. 3: The effect of UV-driven changes in vegetation on atmospheric CO2 and surface temperature.

Data availability

All relevant JULES and NIWA–UKCA model output and input data have been archived (https://doi.org/10.5281/zenodo.4733883).

Code availability

The JULES code for these simulations is available on the Met Office Science Repository System (MOSRS; https://code.metoffice.gov.uk/trac/jules; registration required) in revision 15798. Simulations were run using the Rose suite u-bb620, also available through MOSRS. The NIWA–UKCA CCM is based on the HadGEM3 climate model, which is available under licence. Please contact O.M. (olaf.morgenstern@niwa.co.nz) for details.

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Acknowledgements

P.J.Y. was supported by the UK Engineering and Physical Science Research Council (grant EP/R01860X/1), the Natural Environment Research Council (grant NE/R004927/1) and the Faculty of Science and Technology at Lancaster University. A.B.H. acknowledges funding from the UK Engineering and Physical Science Research Council (Fellowship EP/N030141/1) and the Natural Environment Research Council (grant NE/P019951/1). C.H. acknowledges a UK National Capability grant given to the UK Centre for Ecology and Hydrology. O.M. was supported by the NZ Government’s Strategic Science Investment Fund (SSIF) through the NIWA programme CACV. L.D.O. is supported by the NASA Modeling, Analysis, and Prediction programme. S.M. and R.R.G. are supported by the National Center for Atmospheric Research, which is a major facility sponsored by the US National Science Foundation under cooperative agreement number 1852977. We acknowledge the contribution of New Zealand’s national high-performance computing facilities to the results of this research, provided by the NZ eScience Infrastructure (NeSI) and funded jointly by NeSI’s collaborator institutions and through the NZ Ministry for Business, Innovation and Employment’s Research Infrastructure Programme.

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Contributions

P.J.Y. conceived the initial study on the basis of conversations with N.D.P. P.J.Y., A.B.H. and C.H. designed and constructed the modelling framework and the simulations, performed the analysis and, with N.D.P., wrote the manuscript. O.M., P.A.N., L.D.O., S.M. and R.R.G. provided model simulation data to run the framework and input to the parameterizations used, and contributed to writing the manuscript.

Corresponding author

Correspondence to Paul J. Young.

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The authors declare no competing interests.

Additional information

Peer review information Nature thanks Pedro J. Aphalo, Benjamin Felzer, Veerabhadran Ramanathan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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 Effects on NPP for different latitude bands.

ac, NPP time series data from JULES, as per Fig. 2a, but for 30°–60° N (a), 30° S–30° N (b) and 55°–30° S (c).

Extended Data Table 1 Effect of UV on CO2 and global-mean air temperature for different scenarios
Extended Data Table 2 The UVplant meta-analyses that informed our simulations

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Young, P.J., Harper, A.B., Huntingford, C. et al. The Montreal Protocol protects the terrestrial carbon sink. Nature 596, 384–388 (2021). https://doi.org/10.1038/s41586-021-03737-3

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