Preprints
https://doi.org/10.5194/egusphere-2022-218
https://doi.org/10.5194/egusphere-2022-218
 
16 May 2022
16 May 2022
Status: this preprint is open for discussion.

The ozone–climate penalty over South America and Africa by 2100

Flossie Brown1, Gerd A. Folberth2, Stephen Sitch3, Susanne Bauer4,5, Marijin Bauters6, Pascal Boeckx6, Alexander W. Cheesman3,7, Makoto Deushi8, Inês Dos Santos6, Corinne Galy-Lacaux9, James Haywood1,2, James Keeble10,11, Lina M. Mercado2,12, Fiona M. O'Connor2, Naga Oshima8, Kostas Tsigaridis4,5, and Hans Verbeeck6 Flossie Brown et al.
  • 1College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
  • 2College of Life and Environmental Sciences, University of Exeter, Exeter, UK
  • 3UK Met Office Hadley Centre, Exeter, UK
  • 4Center for Climate Systems Research, Columbia University, New York, NY, USA
  • 5NASA Goddard Institute for Space Studies, New York, NY, USA
  • 6Department of Environment, Ghent University, Ghent, Belgium
  • 7Centre for Tropical Environmental and Sustainability Science, James Cook University, Australia
  • 8Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Ibaraki, Japan
  • 9Laboratoire d’Aerologie, Université Toulouse III Paul Sabatier, CNRS, Toulouse, France
  • 10Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
  • 11National Centre for Atmospheric Science (NCAS), University of Cambridge, UK
  • 12UK Centre for Ecology and Hydrology, Wallingford, UK

Abstract. Climate change has the potential to increase surface ozone (O3) concentrations, known as the ‘ozone–climate penalty’, through changes to atmospheric chemistry, transport and dry deposition. In the tropics, the response of surface O3 to changing climate is relatively understudied, but has important consequences for air pollution, human and ecosystem health. In this study, we evaluate the change in surface O3 due to climate change over South America and Africa using 3 state-of-the-art Earth system models that follow the Shared Socioeconomic Pathway 3 7.0 emissions scenario from CMIP6. To quantify the changes driven by climate change alone, we evaluate the difference between end of the century predictions for simulations which include climate change and simulations with the same emissions scenario but with a fixed present-day climate. We find that by 2100, models predict an ozone–climate penalty in areas where O3 is already predicted to be high due to the impacts of precursor emissions, namely urban and biomass burning areas, although on average models predict a decrease in surface O3 due to climate change. We identify a small but robust positive trend in annual mean surface O3 over polluted areas. Additionally, during biomass burning seasons, seasonal mean O3 concentrations increase by 15 ppb (model range 12 to 18 ppb) in areas with substantial biomass burning such as the arc of deforestation in the Amazon. The ozone–climate penalty in polluted areas is shown to be driven by an increased rate of O3 chemical production, which is strongly influenced by NOx concentrations and is therefore specific to the emissions pathway chosen. Multiple linear regression finds the change in NOx concentration to be a strong predictor of the change in O3 production whereas increased isoprene emission rate is positively correlated with increased O3 destruction, suggesting NOx-limited conditions over the majority of tropical Africa and South America. However, models disagree on the role of climate change in remote, low-NOx regions, partly because of significant differences in NOx concentrations produced by each model. We also find that the magnitude and location of the ozone–climate penalty in the Congo basin has greater inter-model variation than in the Amazon, so further model development and validation is needed to constrain the response in central Africa. We conclude that if the climate were to change according to the emissions scenario used here, models predict that forested areas in biomass burning locations and urban populations will be at increasing risk of high O3 exposure.

Flossie Brown et al.

Status: open (until 10 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-218', William Collins, 08 Jun 2022 reply
  • RC2: 'Comment on egusphere-2022-218', Anonymous Referee #2, 29 Jun 2022 reply

Flossie Brown et al.

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Short summary
Surface ozone can decrease plant productivity and impair human health. In this study, we evaluate the change in surface ozone due to climate change over South America and Africa using Earth system models. We find that if the climate were to change according to the worst-case scenario used here, models predict that forested areas in biomass burning locations and urban populations will be at increasing risk of ozone exposure, but other areas will experience a climate benefit.