Articles | Volume 17, issue 19
Research article
12 Oct 2017
Research article |  | 12 Oct 2017

Projected global ground-level ozone impacts on vegetation under different emission and climate scenarios

Pierre Sicard, Alessandro Anav, Alessandra De Marco, and Elena Paoletti

Abstract. The impact of ground-level ozone (O3) on vegetation is largely under-investigated at the global scale despite large areas worldwide that are exposed to high surface O3 levels. To explore future potential impacts of O3 on vegetation, we compared historical and projected surface O3 concentrations simulated by six global atmospheric chemistry transport models on the basis of three representative concentration pathways emission scenarios (i.e. RCP2.6, 4.5, 8.5). To assess changes in the potential surface O3 threat to vegetation at the global scale, we used the AOT40 metric. Results point out a significant exceedance of AOT40 in comparison with the recommendations of UNECE for the protection of vegetation. In fact, many areas of the Northern Hemisphere show that AOT40-based critical levels will be exceeded by a factor of at least 10 under RCP8.5. Changes in surface O3 by 2100 worldwide range from about +4–5 ppb in the RCP8.5 scenario to reductions of about 2–10 ppb in the most optimistic scenario, RCP2.6. The risk of O3 injury for vegetation, through the potential O3 impact on photosynthetic assimilation, decreased by 61 and 47 % under RCP2.6 and RCP4.5, respectively, and increased by 70 % under RCP8.5. Key biodiversity areas in southern and northern Asia, central Africa and North America were identified as being at risk from high O3 concentrations.

Short summary
A few issues about surface ozone, e.g. a better understanding of spatial changes and a better assessment of ozone impacts worldwide, are still challenging. To overcome these issues, this study assessed, for the first time, the spatial and temporal changes in the projected potential ozone impacts on carbon assimilation of vegetation at global scale, by comparing the ozone potential injury at present with that expected at the end of the 21st century from different global chemistry models.
Final-revised paper