References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-6-5143-2006

Change in global aerosol composition since preindustrial times

Tsigaridis

¹ ⁶ Krol

² Dentener

F. J.

³ Balkanski

⁴ Lathière

⁴ Metzger

⁵ Hauglustaine

D. A.

⁴ Kanakidou

Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, P.O. Box 2208, 71003, Voutes, Heraklion, Greece

Netherlands Institute for Space Research, Utrecht, Netherlands and Wageningen University and Research Center, Wageningen, Netherlands

European Commission, Joint Research Centre, Institute for Environment and Sustainability, Climate Change Unit, Ispra, Italy

Laboratoire des Sciences du Climat et de l'Environnement, 91191 Gif-sur-Yvette Cedex, France

Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, Germany

now at: Laboratoire des Sciences du Climat et de l'Environnement, 91191 Gif-sur-Yvette Cedex, France

10 11 2006

6 12 5143 5162

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/6/5143/2006/acp-6-5143-2006.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/5143/2006/acp-6-5143-2006.pdf

To elucidate human induced changes of aerosol load and composition in the atmosphere, a coupled aerosol and gas-phase chemistry transport model of the troposphere and lower stratosphere has been used. The present 3-D modeling study focuses on aerosol chemical composition change since preindustrial times considering the secondary organic aerosol formation together with all other main aerosol components including nitrate. In particular, we evaluate non-sea-salt sulfate (nss-SO4=), ammonium (NH4+), nitrate (NO3−), black carbon (BC), sea-salt, dust, primary and secondary organics (POA and SOA) with a focus on the importance of secondary organic aerosols. Our calculations show that the aerosol optical depth (AOD) has increased by about 21% since preindustrial times. This enhancement of AOD is attributed to a rise in the atmospheric load of BC, nss-SO4=, NO3<sup−, POA and SOA by factors of 3.3, 2.6, 2.7, 2.3 and 1.2, respectively, whereas we assumed that the natural dust and sea-salt sources remained constant. The nowadays increase in carbonaceous aerosol loading is dampened by a 34–42% faster conversion of hydrophobic to hydrophilic carbonaceous aerosol leading to higher removal rates. These changes between the various aerosol components resulted in significant modifications of the aerosol chemical composition. The relative importance of the various aerosol components is critical for the aerosol climatic effect, since atmospheric aerosols behave differently when their chemical composition changes. According to this study, the aerosol composition changed significantly over the different continents and with height since preindustrial times. The presence of anthropogenically emitted primary particles in the atmosphere facilitates the condensation of the semi-volatile species that form SOA onto the aerosol phase, particularly in the boundary layer. The SOA burden that is dominated by the natural component has increased by 24% while its contribution to the AOD has increased by 11%. The increase in oxidant levels and preexisting aerosol mass since preindustrial times is the reason of the burden change, since emissions have not changed significantly. The computed aerosol composition changes translate into about 2.5 times more water associated with non sea-salt aerosol. Additionally, aerosols contain 2.7 times more inorganic components nowadays than during the preindustrial times. We find that the increase in emissions of inorganic aerosol precursors is much larger than the corresponding aerosol increase, reflecting a non-linear atmospheric response.

References 1

Adams, P. J., Seinfeld, J. H., Koch, D., Mickley, L., and Jacob, D.: General circulation model assessment of direct radiative forcing by the sulfate-nitrate-ammonium-water inorganic aerosol system, J. Geophys. Res., 106, 1097–1111, 2001.

Anfossi, D., Sandroni, S., and Viarengo, S.: Tropospheric ozone in the nineteenth century: the Moncalieri series, J. Geophys. Res., 96, 17 349–17 353, 1991.

Barth, M. C., Rasch, P. J., Kiehl, J. T., Benkovitz, C. M., and Schwartz, S. E.: Sulfur chemistry in the National Center for Atmospheric Research Community Climate Model: Description, evaluation, features, and sensitivity to aqueous chemistry, J. Geophys. Res., 105, 1387–1415, 2000.

Boucher, O. and Pham, M.: History of sulfate aerosol radiative forcings, Geophys. Res. Lett., 29, 1308, doi:10.1029/2001GL014048, 2002.

Chin, M., Rood, R. B., Lin, S.-J., Müller, J.-F., and Thompson, A. M.: Atmospheric sulfur cycle simulated in the global model GOCART: Model description and global properties, J. Geophys. Res., 105, 24 671–24 687, 2000.

Chuang, C. C., Penner, J. E., Prospero, J. M., Grant, K. E., Rau, G. H., and Kawamoto, K.: Cloud susceptibility and the first aerosol indirect forcing: sensitivity to black carbon and aerosol concentrations, J. Geophys. Res., 107, 4564, doi:10.1029/2000JD000215, 2002.

Chung, S. and Seinfeld, J. H.: Global distribution and climate forcing of carbonaceous aerosols, J. Geophys. Res., 107, 4407, doi:10.1029/2001JD001397, 2002.

Claeys, M., Wang, W., Ion, A. C., Kourtchev, I., Gelencsér, A., and Maenhaut, W.: Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide, Atmos. Environ., 38, 4093–4098, 2004.

Cooke, W. F. and Wilson, J. J. N.: A global black carbon aerosol model, J. Geophys. Res., 101, 19 395–19 409, 1996.

Dentener, F. J., Feichter, J., and Jeuken, A.: Simulation of the transport of Rn$^222$ using on-line and off-line global models at different horizontal resolutions: a detailed comparison with measurements, Tellus, 51B, 573–602, 1999.

Dentener, F., Kinne, S., Bond, T., Boucher, O., Cofala, J., Generoso, S., Ginoux, P., Gong, S., Hoelzemann, J. J., Ito, A., Marelli, L., Penner, J. E., Putaud, J.-P., Textor, C., Schulz, M., van der Werf, G. R., and Wilson, J.: Emissions of primary aerosol and precursor gases in the years 2000 and 1750, prescribed data-sets for AeroCom, Atmos. Chem. Phys., 6, 4321–4344, 2006.

Derwent, R. G., Collins, W. J., Jenkin, M. E., Johnson, C. E., and Stevenson, D. S.: The global distribution of secondary particulate matter in a 3-D lagrangian chemistry transport model, J. Atmos. Chem., 44, 57–95, 2003.

Gery, M. W., Whitten, G. Z., Killus, J. P., and Dodge, M. C.: A photochemical kinetics mechanism for urban and regional scale computer modeling. J. Geophys. Res., 94, 12 925–12 956, 1989.

Gibson, R., Kallberg, P., and Uppala, S.: The ECMWF re-analysis (ERA) project, ECMWF newsletter, 73, 7–17, 1997.

Ginoux, P., Chin, M., Tegen, I., Prospero, J. M., Holben, B., Dubovik, O., and Lin. S.-J.: Sources and distributions of dust aerosols simulated by the GOCART model, J. Geophys. Res., 106, 20 255–20 273, 2001.

Griffin, R. J., Cocker III, D. R., Flagan, R. C., and Seinfeld, J. H.: Organic aerosol formation from oxidation of biogenic hydrocarbons, J. Geophys. Res., 104, 3555–3567, 1999a.

Griffin, R. J., Cocker, D. R., Seinfeld, J. H., and Dabdub, D.: Estimate of global atmospheric aerosol from oxidation of biogenic hydrocarbons, Geophys. Res. Lett., 26, 2721–2724, 1999b.

Grini, A., Myhre, G., Zender, C. S., and Isaksen, I. S. A.: Model simulations of dust sources and transport in the global atmosphere: effects of soil erodibility and wind speed variability, J. Geophys. Res., 110, D02205, doi:10.1029/2004JD005037, 2005.

Guelle, W., Schulz, M., Balkanski, Y., and Dentener, F. J.: Influence of the source formulation on modeling the atmospheric global distribution of sea salt aerosol, J. Geophys. Res., 106, 27 509–27 524, 2001.

Haan, D. and Raynaud, D.: Ice core record of CO variations during the last two millennia: atmospheric implications and chemical interactions within the Greenland ice, Tellus, 50B, 253–262, 1998.

Haan, D., Martinerie, P., and Raynaud, D.: Ice core data of atmospheric carbon monoxide over Antarctica and Greenland during the last 200 years, Geophys. Res. Lett., 23, 2235–2238, 1996.

Hauglustaine, D. A. and Brasseur, G. P.: Evolution of tropospheric ozone under anthropogenic activities and associated radiative forcing of climate, J. Geophys. Res., 106, 32 337–32 360, 2001.

Heald, C. L., Jacob, D. J., Park, R. J., Russell, L. M., Huebert, B. J., Seinfeld, J. H., Liao, H., and Weber, R. J.: A large organic aerosol source in the free troposphere missing from current models, Geophys. Res. Lett., 32, L18889, doi:10.1029/2005GL023831, 2005.

Hegg, D. A., Livingston, J., Hobbs, P. V., Novakov, T., and Russell, P.: Chemical apportionment of aerosol column optical depth off the mid-Adlantic coast of the United States, J. Geophys. Res., 102, 25 293–25 303, 1997.

Hein, R., Crutzen, P. J., and Heimann, M.: An inverse modeling approach to investigate the global atmospheric methane cycle, Global Biogeochem. Cycles, 11, 43–76, 1997.

Henze, D. K. and Seinfeld, J. H.: Global secondary organic aerosol from isoprene oxidation, Geophys. Res. Lett., 33, L09812, doi:10.1029/2006GL025976, 2006.

Hoffmann, T., Odum, J. R., Bowman, F., Collins, D., Klockow, D., Flagan, R. C., and Seinfeld, J. H.: Formation of organic aerosols from the oxidation of biogenic hydrocarbons, J. Atmos. Chem., 26, 189–222, 1997.

Houweling, S., Dentener, F., and Lelieveld, J.: The impact of nonmethane hydrocarbon compounds on tropospheric chemistry, J. Geophys. Res., 103, 10 673–10 696, 1998.

Huebert, B., Bertram, T., Kline, J., Howell, S., Eatough, D., and Blomquist, B.: Measurements of organic and elemental carbon in Asian outflow during ACE-Asia from the NSF/NCAR C-130, J. Geophys. Res., 109, D19S11, doi:10.1029/2004JD004700, 2004.

Intergovernmental Panel on Climate Change (IPCC): Climate change: the scientific basis, Cambridge University Press, UK, 2001.

Ito, A. and Penner, J. E.: Historical emissions of carbonaceous aerosols from biomass and fossil fuel burning for the period 1870–2000, Global Biogeochem. Cycles, 19, GB2028, doi:10.1029/2004GB002374, 2005.

Jaenicke, R.: Abundance of cellular material and proteins in the atmosphere, Science, 308, 73, 2005.

Jeuken, A., Veefkind, J. P., Dentener, F., Metzger, S., and Gonzalez, C. R.: Simulation of the aerosol optical depth over Europe for August 1997 and a comparison with observations, J. Geophys. Res. 106, 28 295–28 311, 2001.

Kanakidou, M., Seinfeld, J. H., Pandis, S. N., Barnes, I., Dentener, F. J., Facchini, M. C., van Dingenen, R., Ervens, B., Nenes, A., Nielsen, C. J., Swietlicki, E., Putaud, J. P., Balkanski, Y., Fuzzi, S., Horth, J., Moortgat, G. K., Winterhalter, R., Myhre, C. E. L., Tsigaridis, K., Vignati, E., Stephanou, E. G., and Wilson, J.: Organic aerosols and global climate modeling: a review, Atmos. Chem. Phys., 5, 1053–1123, 2005a.

Kanakidou, M., Tsigaridis, K., Kalivitis, N., Balis, D., Dentener, F. J., Martins Dos Santos, S., Vignati, E., Wilson, J., Putaud, J.-P., van Dingenen, R., Raes, F., Feichter, J., Kinne, S., Stier, P., Kloster, S., Quaas J., Lawrence, M., Lelieveld, J., Metzger, S., Lang, R., Gazenveld, L., Salzmann, M., Schulz, M., Balkanski, Y., Textor, C., Guibert, S., Boucher, O., Reddy, S., Roelofs, G.-J., Krol, M., Jongen, S., Facchini, M.-C., and Mircea, M.: PHOENICS (Particles of Human Origin Extinguish Natural solar Irradiance in the Climate System) synthesis and integration report, edited by: Kanakidou, M. and Dentener, F. J., Emedia University of Crete, Heraklion, Greece, ISBN 960-88712-0-4, 2005b.

Kanakidou, M., Tsigaridis, K., Dentener, F. J., and Crutzen, P. J.: Human-activity-enhanced formation of organic aerosols by biogenic hydrocarbon oxidation, J. Geophys. Res., 105, 9243–9254, 2000.

Kettle, A. J., Andreae, M. O., Amouroux, D., Andreae, T. W., Bates, T. S., Berresheim, H., Bingemer, H., Boniforti, R., Curran, M. A. J., DiTullio, G. R., Helas, G., Jones, G. B., Keller, M. D., Kiene, R. P., Leck, C., Levasseur, M., Malin, G., Maspero, M., Matrai, P., McTaggart, A. R., Mihalopoulos, N., Nguyen, B. C., Novo, A., Putaud, J. P., Rapsomanikis, S., Roberts, G., Schebeske, G., Sharma, S., Simó, R., Staubes, R., Turner, S., and Uher, G: A global database of sea surface dimethyl sulfide (DMS) measurements and a procedure to predict sea surface DMS as a function of latitude, longitude, and month, Global Biogeochem. Cycles, 13, 399–444, 1999.

Kiehl, J. T., Schneider, T. L., Rasch, P. J., Barth, M. C., and Wong, J.: Radiative forcing due to sulphate aerosols from simulations with the National Center for Atmospheric Research Community Climate Model, Version 3, J. Geophys. Res., 105, 1441–1457, 2000.

Kirkevåg, A. and Iversen, T.: Global direct radiative forcing by process-parameterized aerosol optical properties, J. Geophys. Res., 107, 4433, doi:10.1029/2001JD000886, 2002.

Koch, D., Park, J., and del Genio, A.: Clouds and sulfate are anticorrelated: A new diagnostic for global sulphur models, J. Geophys. Res., 108, 4781, doi:10.1029/2003JD003621, 2003.

Koch, D.: Transport and direct radiative forcing of carbonaceous and sulfate aerosols in the GISS GCM, J. Geophys. Res., 106, 20 311–20 332, 2001.

Lathière, J., Hauglustaine, D. A., Friend, A., De Noblet-Ducoudré, N., Viovy, N., and Folberth, G.: Impact of climate variability and land use changes on global biogenic volatile organic compound emissions, Atmos. Chem. Phys., 6, 2129–2146, 2006.

Lathière, J., Hauglustaine, D. A., De Noblet-Ducoudré, N., Krinner, G., and Folberth, G. A.: Past and future changes in biogenic volatile organic compound emissions simulated with a global dynamic vegetation model, Geophys. Res. Lett., 32, L20818, doi:10.1029/2005GL024164, 2005.

Lelieveld, J. and Dentener, F. J.: What controls tropospheric ozone?, J. Geophys. Res., 105, 3531–3551, 2000.

Liao, H., Seinfeld, J. H., Adams, P. J., and Mickley, L. T.: Global radiative forcing of coupled tropospheric ozone and aerosols in a unified general circulation model, J. Geophys. Res., 109, D16207, doi:10.1029/2003JD004456, 2004.

Liousse, C., Penner, J. E., Chuang, C., Walton, J. J., Eddleman, H., and Cachier, H.: A global three-dimensional model study of carbonaceous aerosols, J. Geophys. Res., 101, 19 411–19 432, 1996.

Luo, C., Mahowald, N. M., and del Corral, J.: Sensitivity study of meteorological parameters on mineral aerosol mobilization, transport, and distribution, J. Geophys. Res., 108, 4447, doi:10.1029/2003JD003483, 2003.

Marenco, A., Gouget, H., Nédélec, P., Pagès, J.-P., and Karcher, F.: Evidence of a long-term increase in tropospheric ozone from Pic du Midi data series: concequences – positive radiative forcing, J. Geophys. Res., 99, 16 617–16 632, 1994.

Mayewski, P. A., Lyons, W. B., Spencer, M. J., Twickler, M., Dansgaard, W., Koci, B., Davidson, C. I., and Honrath, R. E.: Sulfate and nitrate concentrations from a south Greenland ice core, Science, 232, 975–977, 1986.

Menon, S., Del Genio, A. D., Koch, D., and Tselioudis, G.: GCM simulations on the aerosol indirect effect: sensitivity to cloud parameterization and aerosol burden, J. Atmos. Sci., 59, 692–713, 2002.

Metzger, S., Dentener, F., Pandis, S. N., and Lelieveld, J.: Gas/aerosol partitioning: 1. A computationally efficient model, J. Geophys. Res., 107, doi:10.1029/2001JD001102, 2002.

Miller, R. L., Tegen, I., and Perlwitz, J.: Surface radiative forcing by soil dust aerosols and the hydrologic cycle, J. Geophys. Res., 109, D04203, doi:10.1029/2003JD004085, 2004.

O'Dowd, C. D., Facchini, M. C., Cavalli, F., Ceburnis, D., Mircea, M., Decesari, S., Fuzzi, S., Yoon, Y. J., and Putaud, J.-F.: Biogenically driven organic contribution to marine aerosol, Nature, 431, 676–680, 2004.

Odum, J. R., Jungkamp, T. P. W., Griffin, R. J., Flagan, R. C., and Seinfeld, J. H.: The atmospheric aerosol-forming potential of whole gasoline vapor, Science, 276, 96–99, 1997.

Patterson, E. M.: Optical properties of the crystal aerosol – relation to chemical and physical characteristics, J. Geophys. Res., 86, 3236–3246, 1981.

Pavelin, E. G., Johnson, C. E., Rughooputh, S., and Toumi, R.: Evaluation of preindustrial ozone measurements made using Schönbein's method, Atmos. Environ., 33, 919–929, 1999.

Presto, A. A., Huff Hartz, K. E., and Donahue, N. M.: Secondary organic aerosol production from terpene ozonolysis. 2. Effect of NOx concentration, Environ. Sci. Technol., 39, 7046–7054, 2005.

Putaud, J. P., Raes, F., Van Dingenen, R., Brüggemann, E., Facchini, M. C., Decesari, S., Fuzzi, S., Gehrig, R., Hüglin, C., Laj, P., Lorbeer, G., Maenhaut, W., Mihalopoulos, N., Müller, K., Querol, X., Rodriguez, S., Schneider, J., Spindler, G., ten Brink, H., Tørseth, K., and Wiedensohler, A.: A European aerosol phenomenology 2: chemical characteristics of particulate matter at kerbside, urban, rural and background sites in Europe, Atmos. Environ., 38, 2579–2595, 2004.

Rasch, P. J., Barth, M. C., Kiehl, J. T., Schwartz, S. E., and Benkovitz, C. M.: A description of the global sulfur cycle and its controlling processes in the National Center for Atmospheric Research Community Climate Model, Version 3, J. Geophys. Res., 105, 1367–1385, 2000.

Reddy, M. S. and Boucher, O.: A study of the global cycle of carbonaceous aerosols in the LMDZT general circulation model, J. Geophys. Res., 109, D14202, doi:10.1029/2003JD004048, 2004.

Rotstayn, L. D. and Lohmann, U.: Simulation of the tropospheric sulfur cycle in a global model with a physically based cloud scheme, J. Geophys. Res., 107, 4592, doi:10.1029/2002JD002128, 2002.

Sandroni, S. and Alfonsi, D.: Historical data of surface ozone at tropical latitudes, Sci. Total Environ., 148, 23–29, 1994.

Sandroni, S., Alfonsi, D., and Viarengo, S.: Surface ozone levels at the end of nineteenth century in South America, J. Geophys. Res., 97, 2535–2539, 1992.

Seinfeld, J. H. and Pandis, S. N.: Atmospheric chemistry and physics: from air pollution to climate change, John Wiley, New York, 1998.

Shettle, E. P. and Fenn, R. W.: Models for the aerosols of the lower atmosphere and the effects of humidity variations on their optical properties, AFGL-TR-79-0214, Environmental Research Paper No. 675, NTIS, ADA 085851, 94 pp.

Shindell, D. T. and Faluvegi, G.: An exploration of ozone changes and their radiative forcing prior to the chlorofluorocarbon era, Atmos. Chem. Phys., 2, 363–374, 2002.

Sigg, A. and Neftel, A.: Evidence for a 50% increase in H2O2 over the past 200 years from a Greenland ice core, Nature, 351, 557–559, 1991.

Song, C., Na, K., and Cocker III, D. R.: Impact of hydrocarbon to NOx ratio on secondary organic aerosol formation, Environ. Sci. Technol., 39, 3143–3149, 2005.

Stier, P., Feichter, J., Kinne, S., Kloster, S., Vignati, E., Wilson, J., Ganzeveld, L., Tegen, I., Werner, M., Balkanski, Y., Schultz, M., Boucher, O., Minikin, A., and Petzold, A.: The aerosol-climate model ECHAM-HAM, Atmos. Chem. Phys., 5, 1125–1156, 2005.

Stier, P., Feichter, J., Roeckner, E., Kloster, S., and Esch, M.: The evolution of the global aerosol system in a transient climate simulation from 1860 to 2100, Atmos. Chem. Phys., 6, 3059–3076, 2006.

Textor, C., Schulz, M., Guibert, S., Kinne, S., Balkanski, Y., Bauer, S., Berntsen, T., Berglen, T., Boucher, O., Chin, M., Dentener, F. J., Diehl, T., Easter, R., Feichter, H., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Horowitz, L., Huang, P., Isaksen, I. S. A., Iversen, T., Kloster, S., Koch, D., Kirkevåg, A., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J.-F., Liu, X., Montanaro, V., Myhre, G., Penner, J., Pitari, G., Reddy, S., Seland, Ø, Stier, P., Takemura, T., and Tie, X.: Analysis and quantification of the diversities of aerosol life cycles within AeroCom, Atmos. Chem. Phys., 6, 1777–1813, 2006.

Tegen, I., Hollrig, P., Chin, M., Fung, I., Jacob, D., and Penner, J.: Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results, J. Geophys. Res., 102, 23 895–23 915, 1997.

Tie, X., Madronich, S., Walters, S., Edwards, D. P., Ginoux, P., Mahowald, N., Zhang, R. Y., Lou, C., and Brasseur, G.: Assessment of the global impact of aerosols on tropospheric oxidants, J. Geophys. Res., 110, D03204, doi:10.1029/2004JD005359, 2005.

Tsigaridis, K. and Kanakidou, M.: Global modelling of secondary organic aerosol in the troposphere: A sensitivity analysis, Atmos. Chem. Phys., 3, 1849–1869, 2003.

Tsigaridis, K., Lathière, J., Kanakidou, M., and Hauglustaine, D. A.: Naturally driven variability in the global secondary organic aerosol over a decade, Atmos. Chem. Phys., 5, 1891–1904, 2005.

Van Aardenne, J. A., Dentener, F. J., Olivier, J. G. J., Klein Goldewijk, C. G. M., and Lelieveld, J.: A 1$^\circ\times1^\circ$ resolution data set of historical anthropogenic trace gas emissions for the period 1890–1990, Global Biogeochem. Cycles, 15, 909–928, 2001.

Veefkind, P.: Aerosol satellite remote sensing, PhD Thesis, Utrecht University, The Netherlands, 1999.

Volz, A. and Kley, D.: Evaluation of the Montsouris series ozone measurements made in the nineteenth sentury, Nature, 332, 240–242, 1988.

Volz, F. E.: Infrared optical-constants of ammonium sulfate, sahara dust, volcanic pumice, and flyash, Appl. Opt., 12, 564–568, 1973.

Wang, Y. and Jacob, D. J.: Anthropogenic forcing on tropospheric ozone and OH since preindustrial times, J. Geophys. Res., 103, 31 123–31 135, 1998.

Zender, C. S., Bian, H., and Newman, D.: Mineral Dust Entrainment and Deposition (DEAD) model: Description and 1990s dust climatology, J. Geophys. Res., 108, 4416, doi:10.1029/2002JD002775, 2003.