ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-437-2012 Have primary emission reduction measures reduced ozone across Europe? An analysis of European rural background ozone trends 1996–2005 Wilson R. C. 1 Fleming Z. L. 2 Monks P. S. 1 Clain G. 3 4 Henne S. 5 Konovalov I. B. 6 7 Szopa S. 4 Menut L. 3 Department of Chemistry, University of Leicester, University Road, Leicester, UK National Centre for Atmospheric Science, Department of Chemistry, University of Leicester, University Road, Leicester, UK Laboratoire de Météorologie Dynamique, École Polytechnique, 91128 Palaiseau, France Laboratoire de Sciences du Climat et de l'Environnement, Gif-sur-Yvette, 91191 France Empa, Swiss Federal Laboratories for Materials Testing and Research, Dübendorf, Switzerland Institute of Applied Physics, Russian Academy of Sciences, Nizhniy Novgorod, Russia Laboratoire Inter-Universitaire de Systèmes Atmosphériques, CNRS, Université Paris-Est and Université Paris 7, Créteil, France 09 01 2012 12 1 437 454 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/437/2012/acp-12-437-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/437/2012/acp-12-437-2012.pdf

National and European legislation over the past 20 yr, and the modernisation or removal of industrial sources, have significantly reduced European ozone precursor emissions. This study quantifies observed and modelled European ozone annual and seasonal linear trends from 158 harmonised rural background monitoring stations over a constant time period of a decade (1996–2005). Mean ozone concentrations are investigated, in addition to the ozone 5th percentiles as a measure of the baseline or background conditions, and the 95th percentiles that are representative of the peak concentration levels. This study aims to characterise and quantify surface European ozone concentrations and trends and assess the impact of the changing anthropogenic emission tracers on the observed and modelled trends. <br><br> Significant (<i>p</i><0.1) positive annual trends in ozone mean, 5th and 95th percentiles are observed at 54 %, 52 % and 45 % of sites respectively (85 sites, 82 sites and 71 sites). Spatially, sites in central and north-western Europe tend to display positive annual ozone trends in mean, 5th and 95th percentiles. Significant negative annual trends in ozone mean 5th and 95th percentiles are observed at 11 %, 12 % and 12 % of sites respectively (18 sites, 19 sites and 19 sites) which tend to be located in the eastern and south-western extremities of Europe. European-averaged annual trends have been calculated from the 158 sites in this study. Overall there is a net positive annual trend in observed ozone mean (0.16&plusmn;0.02 ppbv yr<sup>−1</sup> (2σ error)), 5th (0.13&plusmn;0.02 ppbv yr<sup>−1</sup>) and 95th (0.16&plusmn;0.03 ppbv yr<sup>−1</sup>) percentiles, representative of positive trends in mean, baseline and peak ozone. Assessing the sensitivity of the derived overall trends to the constituent years shows that the European heatwave year of 2003 has significant positive influence and 1998 the converse effect; demonstrating the masking effect of inter-annual variability on decadal based ozone trends. <br><br> The European scale 3-D CTM CHIMERE was used to simulate hourly O<sub>3</sub> concentrations for the period 1996–2005. Comparisons between the 158 observed ozone trends to those equivalent sites extracted from regional simulations by CHIMERE better match the observed increasing annual ozone (predominantly in central and north-western Europe) for 5th percentiles, than for mean or 95th ozone percentiles. The European-averaged annual ozone trend in CHIMERE 5th percentiles (0.13&plusmn;0.01 ppbv yr<sup>−1</sup>) matches the corresponding observed trend extremely well, but displays a negative trend for the 95th percentile (−0.03&plusmn;0.02 ppbv yr<sup>−1</sup>) where a positive ozone trend is observed. Inspection of the EU-averaged monthly means of ozone shows that the CHIMERE model is overestimating the summer month O<sub>3</sub> levels. <br><br> In comparison to trends in EMEP emissions inventories, with the exception of Austria-Hungary, we do not find that anthropogenic NO<sub>x</sub> and VOC reductions have a substantial effect on observed annual mean O<sub>3</sub> trends in the rest of Europe. On a ten year time-scale presented in this study, O<sub>3</sub> trends related to anthropogenic NO<sub>x</sub> and VOC reductions are being masked as a result of a number of factors including meteorological variability, changes in background ozone and shifts in source patterns.

 References 2008/50/EC: Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 On Ambient Air Quality And Cleaner Air For Europe, 2008. Anfossi, D., Sandroni, S., and Viarengo, S.: Tropospheric Ozone in the 19th century – the Moncalieri series, J. Geophys. Res., 96, 17349–17352, 1991. Brönnimann, S., Buchmann, B., and Wanner, H.: Trends in near-surface ozone concentrations in Switzerland: the 1990s, Atmos. Environ., 36, 2841–2852, 2002. Cape, J. N.: Surface ozone concentrations and ecosystem health: Past trends and a guide to future projections, Sci. Total Environ., 400, 257– 269, 2008. Carslaw, D. and Ropkins, K.: Open-source tools for analysing air pollution data, Leeds, U.K., 2009. Carslaw, D C.: On the changing seasonal cycles and trends of ozone at Mace Head, Ireland, Atmos. Chem. Phys., 5, 3441–3450, http://dx.doi.org/10.5194/acp-5-3441-2005doi:10.5194/acp-5-3441-2005, 2005. Chan, E.: Regional ground-level ozone trends in the context of meteorological influences across Canada and the eastern United States from 1997 to 2006, J. Geophys. Res., 114, D05301, http://dx.doi.org/10.1029/2008JD010090doi:10.1029/2008JD010090, 2009. Chan, E. and Vet, R J.: Baseline levels and trends of ground level ozone in Canada and the United States, Atmos. Chem. Phys., 10, 8629–8647, http://dx.doi.org/10.5194/acp-10-8629-2010doi:10.5194/acp-10-8629-2010, 2010. Chevalier, A., Gheusi, F., Delmas, R., Ordóñez, C., Sarrat, C., Zbinden, R., Thouret, V., Athier, G., and Cousin, J.-M.: Influence of altitude on ozone levels and variability in the lower troposphere: a ground-based study for western Europe over the period 2001-2004, Atmos. Chem. Phys., 7, 4311–4326, http://dx.doi.org/10.5194/acp-7-4311-2007doi:10.5194/acp-7-4311-2007, 2007. Cleveland, R B., Cleveland, W S., McRae, J E., and Terpenning, I.: STL: A seasonal-trend decomposition procedure based on Loess, J. Official Statistics, 6, 3–73, 1990. Cleveland, W S.: Robust locally weighted regression and smoothing scatterplots, J. Am. Stat. Assoc., 74, 829–836, 1979. Cooper, O., Derwent, D., Collins, B., Doherty, R., Stevenson, D., Stohl, A., and Hess, P.: Conceptual overview of hemispheric or intercontinental transport of ozone and particulate matter, chap. 1, 1–24, United Nations, New York and Geneva, 2010a. Cooper, O R., Parrish, D D., Stohl, A., Trainer, M., Nédz'elec, P., Thouret, V., Cammas, J P., Oltmans, S J., Johnson, B J., Tarasick, D., Leblanc, T., McDermid, I S., Jaffe, D., Gao, R., Stith, J., Ryerson, T., Aikin, K., Campos, T., Weinheimer, A., and Avery, M A.: Increasing springtime ozone mixing ratios in the free troposphere over western North America, Nature, 463, 344–348, 2010b. Derwent, R. G., Jenkin, M., Saunders, S., Pilling, M., Simmonds, P., Passant, N., Dollard, G., Dumitrean, P., and Kent, A.: Photochemical ozone formation in north west Europe and its control, Atmos. Environ., 37, 1983–1991, 2003. Derwent, R. G., Jenkin, M., Passant, N., and Pilling, M.: Photochemical ozone creation potentials (POCPs) for different emission sources of organic compounds under European conditions estimated with a Master Chemical Mechanism, Atmos. Environ., 41, 2570–2579, 2007a. Derwent, R. G., Simmonds, P., Manning, A., and Spain, T.: Trends over a 20-year period from 1987 to 2007 in surface ozone at the atmospheric research station, Mace Head, Ireland, Atmos. Environ., 41, 9091–9098, 2007b. Derwent, R G., Witham, C S., Utembe, S R., Jenkin, M E., and Passant, N R.: Ozone in Central England: the impact of 20 years of precursor emission controls in Europe, Environ. Sci. Pol., 13, 195–204, 2010. EEA: Air Pollution in Europe 1990–2004, EEA Report No2/2007, European Environment Agency, Copenhagen, 2007. Finzi, G. and Lechi, G.: LANDSAT images of urban air pollution in stable meteorological conditions, Il Nuovo Cimento C, 14, 433–443, 1991. Fiore, A M., Jacob, D J., Bey, I., Yantosca, R M., Field, B D., Fusco, A C., and Wilkinson, J G.: Background ozone over the United States in summer: Origin, trend, and contribution to pollution episodes, J. Geophys. Res., 107, 4275, http://dx.doi.org/10.1029/2001JD000982doi:10.1029/2001JD000982, 2002. Fowler, D., Cape, N., Coyle, M., Flechard, C., Kuylenstierna, J., Hicks, K., Derwent, D., Johnson, C., and Stevenson, D.: The global exposure of forests to air pollutants, Water Air Soil Pollut., 116, 5–32, 1999. Fowler, D., Pilegaard, K., Sutton, M., Ambus, P., Raivonen, M., Duyzer, J., Simpson, D., Fagerli, H., Fuzzi, S., Schjoerring, J., Granier, C., Neftel, A., Isaksen, I., Laj, P., Maione, M., Monks, P., Burkhardt, J., Daemmgen, U., Neirynck, J., Personne, E., Wichink-Kruit, R., Butterbach-Bahl, K., Flechard, C., Tuovinen, J., Coyle, M., Gerosa, G., Loubet, B., Altimir, N., Gruenhage, L., Ammann, C., Cieslik, S., Paoletti, E., Mikkelsen, T., Ro-Poulsen, H., Cellier, P., Cape, J., Horváth, L., Loreto, F., Niinemets, U., Palmer, P., Rinne, J., Misztal, P., Nemitz, E., Nilsson, D., Pryor, S., Gallagher, M., Vesala, T., Skiba, U., Brüggemann, N., Zechmeister-Boltenstern, S., Williams, J., O'Dowd, C., Facchini, M., de~Leeuw, G., Flossman, A., Chaumerliac, N., and Erisman, J.: Atmospheric composition change: ecosystems-atmosphere interactions, Atmos. Environ., 43, 5193–5267, 2009. Gerasopoulos, E., Kouvarakis, G., Vrekoussis, M., Kanakidou, M., and Mihalopoulos, N.: Ozone variability in the marine boundary layer of the eastern Mediterranean based on 7-year observations, J. Geophysical Research, 110, D15 309, 2005. Gigzdiene, R. and Girgzdys, A.: Ozone trend and seasonal cycle at the Preila station, in: Tropospheric Ozone Research, Final Report of Subproject TOR-2, EUROTRAC-2, ISS, Munich, 79–83, 2003. Guicherit, R. and Roemer, M.: Tropospheric ozone trends, Chemosphere – Global Change Sci., 2, 167–183, 2000. Haszpra, L., Ferenczi, Z., Lagzi, I., and Turányi, T.: Formation of tropospheric ozone in Hungary, in: Tropospheric Ozone Research, Final Report of Subproject TOR-2, EUROTRAC-2, ISS, Munich, 87–89, 2003. Henne, S., Brunner, D., Folini, D., Solberg, S., Klausen, J., and Buchmann, B.: Assessment of parameters describing representativeness of air quality in-situ measurement sites, Atmos. Chem. Phys., 10, 3561–3581, http://dx.doi.org/10.5194/acp-10-3561-2010doi:10.5194/acp-10-3561-2010, 2010. Hess, A., Iyer, H., and Malm, W.: Linear trend analysis: a comparison of methods, Atmos. Environ., 35, 5211–5222, http://dx.doi.org/10.1016/S1352-2310(01)00342-9doi:10.1016/S1352-2310(01)00342-9, 2001. Hirsch, R M., Slack, J., and Smith, R A.: Techniques of trend analysis for monthly water-quality data, Water Resour. Res., 18, 107–121, 1982. IPCC, ed.: Climate Change 2007: The physical science basis. Contribution of working group I to the fourth assessment report of the Intergovernmental Panel on Climate Change. Chapter 1, Historical overview of climate change, Cambridge University Press, Cambridge, 2007. Jaffe, D. and Ray, J.: Increase in surface ozone at rural sites in the western US, Atmos. Environ., 41, 5452–5463, 2007. Jaffe, D., Bertschi, I., Jaeglé, L., Novelli, P., Reid, J S., Tanimoto, H., Vingarzan, R., and Westphal, D L.: Long-range transport of Siberian biomass burning emissions and impact on surface ozone in western North America, Geophys. Res. Letters, 311, L16106, http://dx.doi.org/10.1029/2004GL020093doi:10.1029/2004GL020093, 2004. Jenkin, M E.: Trends in ozone concentration distributions in the UK since 1990: Local, regional and global influences, Atmos. Environ., 42, 5434–5445, 2008. Jonson, J E., Simpson, D., Fagerli, H., and Solberg, S.: Can we explain the trends in European ozone levels?, Atmos. Chem. Phys., 6, 51–66, http://dx.doi.org/10.5194/acp-6-51-2006doi:10.5194/acp-6-51-2006, 2006. Keating, T. and Zuber, A.: Hemispheric transport of air pollution 2007, Air Pollution Studies No. 16, UNECE, Geneva, 2007. Konovalov, I B., Beekmann, M., Burrows, J P., and Richter, A.: Satellite measurement based estimates of decadal changes in European nitrogen oxides emissions, Atmos. Chem. Phys., 8, 2623–2641, http://dx.doi.org/10.5194/acp-8-2623-2008doi:10.5194/acp-8-2623-2008, 2008. Koumoutsaris, S., Bey, I., Generoso, S., and Thouret, V.: Influence of El Niño southern oscillation on the interannual variability of tropospheric ozone in the northern midlatitudes, J. Geophys. Res., 113, D19301, http://dx.doi.org/10.1029/2007JD009753doi:10.1029/2007JD009753, 2008. Law, K., Parrish, D., Arnold, S., Chan, E., Chen, G., Cooper, O., Derwent, D., Edwards, D., Jaffe, D., Koch, D., Laj, P., Martin, R., Methven, J., Monks, P. S., Penkett, S. A., Prospero, J., Quinn, P., Remer, L., Staehelin, J., Scheffe, R., Takami, A., Tanimoto, H., Thouret, V., Turquety, S., Zdanowicz, C., and Ziemke, J.: Observational evidence and capabilities related to intercontinental transport of ozone and particualte matter, United Nations, New York and Geneva, chap. 2, 25–75, 2010. Lee, J D., Lewis, A C., Monks, P S., Jacob, M., Hamilton, J F., Hopkins, J R., Watson, N M., Saxton, J E., Ennis, C., Carpenter, L J., Carslaw, N., Fleming, Z., Bandy, B J., Oram, D E., Penkett, S A., Slemr, J., Norton, E., Rickard, A R., Whalley, L K., Heard, D E., Bloss, W J., Gravestock, T., Smith, S C., Stanton, J., Pilling, M J., and Jenkin, M E.: Ozone photochemistry and elevated isoprene during the UK heatwave of august 2003, Atmos. Environ., 40, 7598–7613, 2006. Lindskog, A., Beekmann, M., Monks, P S., Roemer, M., Schuepbach, E., and Solberg, S.: Tropospheric Ozone Research – TOR-2, in: Tropospheric Ozone Research, Final Report of Subproject TOR-2, EUROTRAC-2, ISS, Munich, 1–28, 2003. Monks, P S.: A review of the observations and origins of the spring ozone maximum, Atmos. Environ., 34, 3545–3561, 2000. Monks, P S.: Gas-phase radical chemistry in the troposphere, Chem. Soc. Rev., 34, 376–395, 2005. Monks, P. S., Granier, C., Fuzzi, S., Stohl, A., Williams, M., Akimoto, H., Amann, M., Baklanov, A., Baltensperger, U., Bey, I., Blake, N., Blake, R., Carslaw, K., Cooper, O., Dentener, F., Fowler, D., Fragkou, E., Frost, G., Generoso, S., Ginoux, P., Grewe, V., Guenther, A., Hansson, H., Henne, S., Hjorth, J., Hofzumahaus, A., Huntrieser, H., Isaksen, I., Jenkin, M., Kaiser, J., Kanakidou, M., Klimont, Z., Kulmala, M., Laj, P., Lawrence, M., Lee, J., Liousse, C., Maione, M., McFiggans, G., Metzger, A., Mieville, A., Moussiopoulos, N., Orlando, J., O'Dowd, C., Palmer, P., Parrish, D., Petzold, A., Platt, U., Pöschl, U., Prévôt, A., Reeves, C., Reimann, S., Rudich, Y., Sellegri, K., Steinbrecher, R., Simpson, D., ten Brink, H., Theloke, J., van~der Werf, G., Vautard, R., Vestreng, V., Vlachokostas, C., and von Glasow, R.: Atmospheric composition change – global and regional air quality, Atmos. Environ., 43, 5268–5350, 2009. National Research Council: Global sources of local pollution: An assessment of long-range transport of key air pollutants to and from the United States, The National Academies Press, Washington, DC, USA, 248 pp., 2009. Oltmans, S. J., Lefohn, A., Harris, J., Galbally, I., Scheel, H., Bodeker, G., Brunke, E., Claude, H., Tarasick, D., Johnson, B., Simmonds, P., Shadwick, D., Anlauf, K., Hayden, K., Schmidlin, F., Fujimoto, T., Akagi, K., Meyer, C., Nichol, S., Davies, J., Redondas, A., and Cuevas, E.: Long-term changes in tropospheric ozone, Atmos. Environ., 40, 3156–3173, 2006. Oltmans, S J., Galbally, I E., Brunke, E.-G., Meyer, C P., Lathrop, J A., Johnson, B J., Shadwick, D S., Cuevas, E., Schmidlin, F J., Tarasick, D W., Claude, H., Kerr, J B., Uchino, O., and Mohnen, V.: Trends of ozone in the troposphere, Geophys. Res. Lett., 25, 139–142, http://dx.doi.org/10.1029/97GL03505doi:10.1029/97GL03505, 1998. Oltmans, S J., Lefohn, A S., Harris, J M., and Shadwick, D S.: Background ozone levels of air entering the west coast of the US and assessment of longer-term changes, Atmos. Environ., 42, 6020–6038, 2008. Ordóñez, C., Mathis, H., Furger, M., Henne, S., Hüglin, C., Staehelin, J., and Prévôt, A. S H.: Changes of daily surface ozone maxima in Switzerland in all seasons from 1992 to 2002 and discussion of summer 2003, Atmos. Chem. Phys., 5, 1187–1203, http://dx.doi.org/10.5194/acp-5-1187-2005doi:10.5194/acp-5-1187-2005, 2005. Parrish, D D.: Critical evaluation of US on-road vehicle emission inventories, Atmos. Environ., 40, 2288–2300, 2006. Parrish, D. D., Millet, D., and Goldstein, A.: Increasing ozone in marine boundary layer inflow at the west coasts of North America and Europe, Atmos. Chem. Phys., 9, 1303–1323, http://dx.doi.org/10.5194/acp-9-1303-2009doi:10.5194/acp-9-1303-2009, 2009. Parrish, D D., Trainer, M., Hereid, D., Williams, E J., Olszyna, K J., Harley, R A., Meagher, J F., and Fehsenfeld, F C.: Decadal change in carbon monoxide to nitrogen oxide ratio in U.S. vehicular emissions, J. Geophys. Res., 107, 4140, http://dx.doi.org/10.1029/2001JD000720doi:10.1029/2001JD000720, 2002. Pavelin, E., Johnson, C., Rughooputh, S., and Toumi, R.: Evaluation of pre-industrial surface ozone measurements made using Schönbein's method, Atmos. Environ., 33, 919–929, 1999. R Development Core Team: An introduction to R, R Foundation for Statistical Computing, Vienna, Austria, 2009. Sandroni, S., Anfossi, D., and Viarengo, S.: Surface ozone levels at the end of the 19th century in South America, J. Geophys. Res.-Atmos., 97, 2535–2539, 1992. Schmidt, H., Derognat, C., Vautard, R., and Beekmann, M.: A comparison of simulated and observed ozone mixing ratios for the summer of 1998 in Western Europe, Atmos. Environ., 35, 6277–6297, 2001. Sicard, P., Coddeville, P., and Galloo, J.: Near-surface ozone levels and trends at rural stations in France over the 1995-2003 period, Environ. Monit. Assess., 156, 141–157, 2009. Sicard, P., Mangin, A., Hebel, P., and Malla, P.: Detection and estimation trends linked to air quality and mortality on French Riviera over the 1990-2005 period, Sci. Total Environ., 408, 1943–1950, 2010. Simmonds, P G., Derwent, R G., Manning, A L., and Spain, G.: Significant growth in surface ozone at Mace Head, Ireland, 1987–2003, Atmos. Environ., 38, 4769–4778, 2004. Solberg, S., Hov, O., Søvde, A., Isaksen, I. S A., Coddeville, P., Backer, H D., Forster, C., Orsolini, Y., and Uhse, K.: European surface ozone in the extreme summer 2003, Geophys. Res. Lett., 113, D07307, http://dx.doi.org/10.1029/2007JD009098doi:10.1029/2007JD009098, 2008. Solberg, S., Jonson, J E., Horalek, J., Larssen, S., and de~Leeuw, F.: Assessment of ground-level ozone in EEA member countries, with a focus on long-term trends, EEA Report No7/2009, European Environment Agency, Copenhagen, 2009. Staehelin, J., Thudium, J., Buehler, R., Volz-Thomas, A., and Graber, W.: Trends in surface ozone concentrations at Arosa (Switzerland), Atmos. Environ., 28, 75–87, 1994. Szopa, S., Hauglustaine, D., Vautard, R., and Menut, L.: Future global tropospheric ozone changes and impact on European air quality, Geophys. Res. Lett., 33, L14805, http://dx.doi.org/10.1029/2006GL025860doi:10.1029/2006GL025860, 2006. Tanimoto, H., Ohara, T., and Uno, I.: Asian anthropogenic emissions and decadal trends in springtime tropospheric ozone over Japan: 1998–2007, Geophysical Research Letters, 36, L23802, http://dx.doi.org/10.1029/2009GL041382doi:10.1029/2009GL041382, 2009. The Royal Society: Ground-level ozone in the 21st century: future trends, impacts and policy implications, London, UK, 132 pp., 2008. Thompson, M L., Reynolds, J., Cox, L H., Guttorp, P., and Sampson, P D.: A review of statistical methods for the meteorological adjustment of tropospheric ozone, Atmos. Environ., 35, 617–630, http://dx.doi.org/10.1016/S1352-2310(00)00261-2doi:10.1016/S1352-2310(00)00261-2, 2001. Tripathi, O P., Jennings, S G., O'Dowd, C D., Coleman, L., Leinert, S., O'Leary, B., Moran, E., O'Doherty, S J., and Spain, T G.: Statistical analysis of eight surface ozone measurement series for various sites in Ireland, J. Geophys. Res., 115, D19302, http://dx.doi.org/10.1029/2010JD014040doi:10.1029/2010JD014040, 2010. Vautard, R., Honor, C., Beekmann, M., and Rouil, L.: Simulation of ozone during the August 2003 heat wave and emission control scenarios, Atmos. Environ., 39, 2957–2967, 2005. Vautard, R., Szopa, S., Beekmann, M., Menut, L., Hauglustaine, D A., Rouil, L., and Roemer, M.: Are decadal anthropogenic emission reductions in Europe consistent with surface ozone observations?, Geophys. Res. Lett., 33, L13810, http://dx.doi.org/10.1029/2006GL026080doi:10.1029/2006GL026080, 2006. Vestreng, V., Rigler, E., Adams, M., Kindbom, K., Pacyna, J., Denier van~der Gon, H., Reis, S., and Travnikov, O.: Inventory review 2006, Emission data reported to LRTAP and NEC Directive, Stage 1, 2 and 3 review and Evaluation of inventories of HM and POPs, Tech. Rep. 1/2006, EMEP/MSC-W Technical Report, 2006. Vestreng, V., Ntziachristos, L., Semb, A., Reis, S., Isaksen, I. S A., and Tarrasón, L.: Evolution of NO<sub>x</sub> emissions in Europe with focus on road transport control measures, Atmos. Chem. Phys., 9, 1503–1520, http://dx.doi.org/10.5194/acp-9-1503-2009doi:10.5194/acp-9-1503-2009, 2009. Vingarzan, V.: A review of surface ozone background levels and trends, Atmos. Environ., 38, 3431–3442, 2004. Volz, A. and Kley, D.: Evaluation of the Montsouris series of ozone measurements made in the nineteenth century, Nature, 332, 240–242, 1988. von Schneidemesser, E., Monks, P S., and Plass-Duelmer, C.: Global comparison of VOC and CO observations in urban areas, Atmos. Environ., 44, 5053–5064, 2010. Voulgarakis, A., Savage, N H., Wild, O., Braesicke, P., Young, P J., Carver, G D., and Pyle, J A.: Interannual variability of tropospheric composition: the influence of changes in emissions, meteorology and clouds, Atmos. Chem. Phys., 10, 2491–2506, http://dx.doi.org/10.5194/acp-10-2491-2010doi:10.5194/acp-10-2491-2010, 2010. Weatherhead, E C., Reinsel, G C., Tiao, G C., Meng, X., Choi, D., Cheang, W., Keller, T., DeLuisi, J., Wuebbles, D J., Kerr, J B., Miller, A J., Oltmans, S J., and Frederick, J E.: Factors affecting the detection of trends: Statistical considerations and applications to environmental data, J. Geophys. Res., 103, 17149–17161, 1998. Weatherhead, E C., Stevermer, A J., and Schwartz, B E.: Detecting environmental changes and trends, Physics and Chemistry of the Earth, 27, 399–403, 2002. WHO: Health aspects of air pollution with particulate matter, ozone and nitrogen dioxide, World Health Organisation, Bonn, 2003. Xu, X., Lin, W., Wang, T., Yan, P., Tang, J., Meng, Z., and Wang, Y.: Long-term trend of surface ozone at a regional background station in eastern China 1991–2006: enhanced variability, Atmos. Chem. Phys., 8, 2595–2607, http://dx.doi.org/10.5194/acp-8-2595-2008doi:10.5194/acp-8-2595-2008, 2008. Zvyagintsev, A. and Tarasova, O.: Trends of surface ozone concentrations in germany and their connections with changes in meteorological variables, Russ. Meteorol. Hydrol., 36, 258–264, 2011.