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Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2017-409
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
11 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).
Large but decreasing effect of ozone on the European carbon sink
Rebecca J. Oliver1, Lina M. Mercado1,2, Stephen Sitch2, David Simpson3,4, Belinda E. Medlyn5, Yan-Shih Lin5, and Gerd A. Folberth6 1Centre for Ecology and Hydrology, Benson Lane, Wallingford, OX10 8BB, UK
2College of Life and Environmental Sciences, University of Exeter, EX4 4RJ, Exeter, UK
3EMEP MSC-W Norwegian Meteorological Institute, PB 43, NO-0313, Oslo, Norway
4Dept. Space, Earth & Environment, Chalmers University of Technology, Gothenburg, SE-41296 Sweden
5Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
6Met Office Hadley Centre, Exeter, UK
Abstract. The capacity of the terrestrial biosphere to sequester carbon and mitigate climate change is governed by the ability of vegetation to remove emissions of CO2 through photosynthesis. Tropospheric O3, a globally abundant and potent greenhouse gas, is, however, known to damage plants, causing reductions in primary productivity, yet the impact of this gas on European vegetation and the land carbon sink is largely unknown. Despite emission control policies across Europe, background concentrations of tropospheric O3 have risen significantly over the last decades due to hemispheric-scale increases in O3 and its precursors. Therefore, plants are exposed to increasing background concentrations, at levels currently causing chronic damage. We use the JULES land-surface model recalibrated for O3 impacts on European vegetation, with an improved stomatal conductance parameterization, to quantify the impact of tropospheric O3, and its interaction with CO2, on gross primary productivity (GPP) and land carbon storage across Europe. A factorial set of model experiments showed that tropospheric O3 can significantly suppress terrestrial carbon uptake across Europe over the period 1901 to 2050. By 2050, simulated GPP was reduced by 4 to 9 % due to plant ozone damage, however, the combined effects of elevated future CO2 (acting to reduce stomatal opening) and reductions in O3 concentrations resulted in reduced O3 damage in the future, contrary to predictions from earlier studies. Reduced land carbon storage resulted from diminished soil carbon stocks consistent with the reduction in GPP. Regional variations are identified with larger impacts shown for temperate Europe compared to boreal regions. These results highlight that the effects of O3 on plant physiology add to the uncertainty of future trends in the land carbon sink and, as such, this should be incorporated into carbon cycle assessments.

Citation: Oliver, R. J., Mercado, L. M., Sitch, S., Simpson, D., Medlyn, B. E., Lin, Y.-S., and Folberth, G. A.: Large but decreasing effect of ozone on the European carbon sink, Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-409, in review, 2017.
Rebecca J. Oliver et al.
Rebecca J. Oliver et al.
Rebecca J. Oliver et al.

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Short summary
Potential gains in terrestrial carbon sequestration over Europe from elevated CO2 can be partially offset by concurrent rises in tropospheric O3. The land-surface model JULES was run in a factorial suite of experiments showing that by 2050 simulated GPP was reduced by 4 to 9 % due to plant O3 damage. Large regional variations exist with larger impacts identified for temperate compared to boreal regions. Plant O3 damage was greatest over the twentieth century and declined into the future.
Potential gains in terrestrial carbon sequestration over Europe from elevated CO2 can be...
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