Future air quality in Europe: a multi-model assessment of projected exposure to ozone

In order to explore future air quality in Europe at the 2030 horizon, two emission scenarios developed in the framework of the Global Energy Assessment including varying assumptions on climate and energy access policies are investigated with an ensemble of six regional and global atmospheric chemistry transport models. <br><br> A specific focus is given in the paper to the assessment of uncertainties and robustness of the projected changes in air quality. The present work relies on an ensemble of chemistry transport models giving insight into the model spread. Both regional and global scale models were involved, so that the ensemble benefits from medium-resolution approaches as well as global models that capture long-range transport. For each scenario a whole decade is modelled in order to gain statistical confidence in the results. A statistical downscaling approach is used to correct the distribution of the modelled projection. Last, the modelling experiment is related to a hind-cast study published earlier, where the performances of all participating models were extensively documented. <br><br> The analysis is presented in an exposure-based framework in order to discuss policy relevant changes. According to the emission projections, ozone precursors such as NO<sub>x</sub> will drop down to 30% to 50% of their current levels, depending on the scenario. As a result, annual mean O<sub>3</sub> will slightly increase in NO<sub>x</sub> saturated areas but the overall O<sub>3</sub> burden will decrease substantially. Exposure to detrimental O<sub>3</sub> levels for health (SOMO35) will be reduced down to 45% to 70% of their current levels. And the fraction of stations where present-day exceedences of daily maximum O<sub>3</sub> is higher than 120 μg m<sup>−3</sup> more than 25 days per year will drop from 43% down to 2 to 8%. <br><br> We conclude that air pollution mitigation measures (present in both scenarios) are the main factors leading to the improvement, but an additional cobenefit of at least 40% (depending on the indicator) is brought about by the climate policy

Evolution of anthropogenic and biomass burning emissions of air pollultants at global and regional scales during the 1980-2010 period

Several different inventories of global and regional anthropogenic and biomass burning emissions are assessed for the 1980-2010 period. The species considered in this study are carbon monoxide, nitrogen oxides, sulfur dioxide and black carbon. The inventories considered include the ACCMIP historical emissions developed in support of the simulations for the IPCC AR5 assessment. Emissions for 2005 and 2010 from the Representative Concentration Pathways (RCPs) are also included. Large discrepancies between the global and regional emissions are identified, which shows that there is still no consensus on the best estimates for surface emissions of atmospheric compounds. At the global scale, anthropogenic emissions of CO, NOx and SO2 show the best agreement for most years, although agreement does not necessarily mean that uncertainty is low. The agreement is low for BC emissions, particularly in the period prior to 2000. The best consensus is for NOx emissions for all periods and all regions, except for China, where emissions in 1980 and 1990 need to be better defined Emissions of CO need better quantification in the USA and India for all periods; in Central Europe, the evolution of emissions during the past two decades needs to be better determined. The agreement between the different SO2 emissions datasets is rather good for the USA, but better quantification is needed elsewhere, particularly for Central Europe, India and China. The comparisons performed in this study show that the use of RCP8.5 for the extension of the ACCMIP inventory beyond 2000 is reasonable, until more global or regional estimates become available. Concerning biomass burning emissions, most inventories agree within 50-80%, depending on the year and season. The large differences between biomass burning inventories are due to differences in the estimates of burned areas from the different available products, as well as in the amount of biomass burned

Evolution of the distribution of tropospheric ozone and its precursores during the 1997-2030 period

As part of the CityZen (Megacity - Zoom for the Environment) European project, global and regional European chemistry transport models were used to simulate the past evolution of the composition of the troposphere during the 1997-2008 period, as well as its future evolution up to 2030. The simulations were performed using a consistent dataset for surface emissions. European emissions for the past period were provided by the European Monitoring and Evaluation Programme (EMEP) and processed by INERIS. The global emissions are given by the MACCity emissions dataset, derived from the ACCMIP (Emissions for Atmospheric Chemistry and Climate Model Intercomparison Project) dataset. We will discuss the consistency between global and regional emissions dataset, focusing on a few regions, and more particularly on Europe, the United States and China. The future emissions are based on the GEA (Global Energy Assessment) scenarios developed by IIASA. Two scenarios will be considered in this study: the first scenario assumes a full implementation of all current and planned air pollution legislation world-wide until 2030. The second scenario assumes, in addition to air quality legislation, implementation of a stringent climate policy corresponding to a 2 degree global temperature target including a moderate energy access policy corresponding to microfinance as well as fuel subsidy. We will discuss the results obtained by the simulations for the full period considered, with a focus on NOx, CO, OH and ozone. We will also discuss comparisons of the simulations provided by the reanalysis of the atmospheric composition from the MACC European project. Comparisons with surface observations of CO and ozone at selected sites located at different latitudes for the 1998-2008 period will be presented. The results of the simulations for the future will also be compared with simulations performed for different scenarios, such as the one provided by the RCPs (Representative Concentration Pathways)

Evolution of the distribution of tropospheric chemical species during the past decade

Megacities, with a population exceeding ten million inhabitants, represent hot spots of emissions that need to be correctly quantified in order to evaluate their effects at the local, regional and global scale. Within the 7th Framework European project CityZen (Megacity - Zoom for the Environment), the impact of changes in emissions on the global distributions of chemical compounds is being assessed, with a focus on the impact of megacities in Europe, Northern Africa and China. The goal of the project is to comprehend the feedbacks between climate change and air quality from the largest world cities at the global and regional scales. In order to simulate the changes in the distribution of gaseous compounds as well as aerosols we have used the MOZART (Model for OZone And Related chemical Tracers) global chemistry transport model. This model is driven by offline meteorological fields: for the present study we have used the meteorological fields provided by the National Center for Environmental Prediction (NCEP). The focus of the study is the 1996-2007 period, during which the changes in the distribution of the chemical compounds related to changes in emissions during that period will be discussed. The global emissions used in the present study are derived from the new dataset developed in support of the next IPCC (Intergovernmental Panel on Climate Change) AR5 report under discussion. We will discuss the methodology we have used to update the IPCC anthropogenic emissions up to year 2007. The new emissions inventory for Europe developed within CityZen for the 1996-2007 period will be discussed and compared with the emissions provided by other inventories. Furthermore, we will discuss the biomass burning inventory used in this work, which provides monthly averaged emissions for the full period of the study. Emissions of biogenic volatile organic compounds are derived from the most recent version of the MEGAN (Model of Emissions of Gases and Aerosols from Nature) model. Simulations covering the considered period will be performed using different combinations of the emissions of the datasets being performed. We will discuss the results of the simulations, focusing more particularly on the simulations using either IPCC dataset or a combined IPCC / European emissions dataset, or different Biogenic Volatile Organic Compounds emissions. We will discuss the changes in the distribution of tropospheric chemical species from the different simulations, considering both gaseous compounds and different types of aerosols

Monitoring the changes in the tropospheric composition over the past two decades using Satellite observations and CTM

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Evaluation of anthropogenic and natural surface emissions of atmospheric chemical compounds

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Air quality trends in Europe over the past decade: a first multi-model assessment

International audienceWe discuss the capability of current state-of-the-art chemistry and transport models to reproduce air quality trends and inter annual variability. Documenting these strengths and weaknesses on the basis of historical simulations is essential before the models are used to investigate future air quality projections. To achieve this, a coordinated modelling exercise was performed in the framework of the CityZEN European Project. It involved six regional and global chemistry-transport models (Bolchem, Chimere, Emep, Eurad, OsloCTM2 and Mozart) simulating air quality over the past decade in the Western European anthropogenic emissions hotspots. Comparisons between models and observations allow assessing the skills of the models to capture the trends in basic atmospheric constituents (NO2, O3, and PM10). We find that the trends of primary constituents are well reproduced (except in some countries - owing to their sensitivity to the emission inventory) although capturing the more moderate trends of secondary species such as O3 is more challenging. Apart from the long term trend, the modelled monthly variability is consistent with the observations but the year-to-year variability is generally underestimated. A comparison of simulations where anthropogenic emissions are kept constant is also investigated. We find that the magnitude of the emission-driven trend exceeds the natural variability for primary compounds. We can thus conclude that emission management strategies have had a significant impact over the past 10 yr, hence supporting further emission reductions strategies