Abstract
Abstract. In the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr, last access: 22 June 2018) project, we study the evolution of surface ozone over the Mediterranean Basin (MB) with a focus on summertime over the time period 2000–2100, using the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) outputs from 13 models. We consider three different periods (2000, 2030 and 2100) and the four Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) to study the changes in the future ozone and its budget. We use a statistical approach to compare and discuss the results of the models. We discuss the behavior of the models that simulate the surface ozone over the MB. The shape of the annual cycle of surface ozone simulated by ACCMIP models is similar to the annual cycle of the ozone observations, but the model values are biased high. For the summer, we found that most of the models overestimate surface ozone compared to observations over the most recent period (1990–2010). Compared to the reference period (2000), we found a net decrease in the ensemble mean surface ozone over the MB in 2030 (2100) for three RCPs: −14 % (−38 %) for RCP2.6, −9 % (−24 %) for RCP4.5 and −10 % (−29 %) for RCP6.0. The surface ozone decrease over the MB for these scenarios is much more pronounced than the relative changes of the global tropospheric ozone burden. This is mainly due to the reduction in ozone precursors and to the nitrogen oxide (NOx = NO + NO2)-limited regime over the MB. For RCP8.5, the ensemble mean surface ozone is almost constant over the MB from 2000 to 2100. We show how the future climate change and in particular the increase in methane concentrations can offset the benefits from the reduction in emissions of ozone precursors over the MB.
Highlights
Several modeling studies have evaluated the future evolution of chemical and dynamical processes and have shown that future changes in ozone precursors have a significant impact on the evolution of tropospheric ozone and surface ozone (e.g., West et al, 2007; Butler et al, 2012)
In the framework of the Chemistry and Aerosol Mediterranean Experiment project (ChArMEx, http://charmex.lsce. ipsl.fr, last access: 22 June 2018), we focused on future changes in surface ozone from 2000 to 2100 above the Mediterranean Basin (MB) using model outputs from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP; Lamarque et al, 2013)
The Mediterranean Basin would likely benefit from both the CH4 and NOx emissions’ control. 4.5 Production, loss and deposition of ozone we focus on the evolution of four ozone budget terms along the 21st century over the MB: production (P), chemical loss (L), production minus chemical loss (P-L) and dry deposition of ozone (D) for all scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) and periods (2000, 2030 and 2100)
Summary
Several modeling studies have evaluated the future evolution of chemical and dynamical processes and have shown that future changes in ozone precursors have a significant impact on the evolution of tropospheric ozone and surface ozone (e.g., West et al, 2007; Butler et al, 2012). At the regional scale, Lacressonnière et al (2014) studied the future changes in surface ozone over Europe and the MB using a chemistry–transport model under the RCP8.5 scenario which corresponds to the pathway with the highest greenhouse gas emissions, leading to a radiative forcing of the order of 8.5 W m−2 at the end of the 21st century. Ipsl.fr, last access: 22 June 2018), we focused on future changes in surface ozone from 2000 to 2100 above the MB using model outputs from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP; Lamarque et al, 2013). The first part consists of a model assessment based on the REF period, in which we compare the outputs of different models to a set of available surface ozone data based on the gridded observations given by Sofen et al (2016). The future evolution of the ozone budget is discussed
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