GAW Report No. 205 - IGAC Project

CHAPTER 6 - EUROPEFigure 1 shows a map of the population density of Europe. For Europe, the bottom-upstatistical and census-based population data plotted here are generally very consistent withtop-down estimates based on analyses of stable night lights; alternate representations of thepopulation are available on the internet, e.g., a mapping by district complied by the IIASA EuropeanRural Development (ERD) Project (http://www.iiasa.ac.at/Research/ERD/DB/mapdb/map_9.htm).The map shows that each of the six European MPCs listed in Table 1 is characterized by a largecentral region with a population density exceeding 1000 persons/km 2 . There are also a handful ofother cities within Europe with population densities as high as this, e.g., Berlin and Madrid, but thetotal populations of these cities are not large enough to generally be classified as Megacities orMPCs for the sake of this overview. Beyond the commonality of a dense core region, however,there are substantial differences in the geographical locations and urban and suburban structure ofthe European MPCs. One interesting feature is that while a large fraction of the MPCs worldwideare either coastal or close to large bodies of water, only one of the European MPCs, Istanbul, isreally a coastal city. London is also relatively close to the coast, while Paris, the Po Valley and theBenelux/Rhine-Ruhr region are all several hundred km away from the nearest coast, and Moscow isthe most land-locked of all megacities worldwide. Further differences in the demographical andgeographical characteristics are elucidated in the discussions of the individual cities, below.Figure 1 - Map of the population density in Europe and western Asia (persons per km 2 ), based on 0.25 o gridded data for2000 from the Centre for International Earth Science Information Network (CIESIN) at Columbia University[http://sedac.ciesin.columbia.edu/gpw/]6.1.2 EmissionsExemplary emissions of key pollutant gases in Europe are depicted in Figure 2. Research onemissions from megacities worldwide has included several studies of city-specific emissions. ForEurope in particular, a significant recent effort has gone into developing a collection of inventoriesfor European cities within the City Delta project [Cuvelier et al., 2007]. Four of the European MPCswere also included in the study of Butler et al. [2008)], which contrasted the emissionscorresponding to 32 MPCs in three widely-used global emissions datasets (EDGAR, RETRO andIIASA) with each other and with city-specific emissions, where available. The comparison showsfrequently large differences (often a factor of two or more) between the emissions for individualcities within the global datasets, and normally large underestimates compared to the city-specificdatasets. This applies especially to Paris, for which the CO emissions in the global datasets rangeover nearly a factor of two, from 263 Gg(CO)/yr (EDGAR) to 490 Gg(CO)/yr (RETRO), and are afactor of 4-7 less than the 1907 Gg(CO)/yr estimated in the City Delta project. The discrepancydetermined for London is smaller, but still exceeding a factor of 2, with a range of 800-1043Gg(CO)/yr from the global inventories versus 1993 Gg(CO)/yr from the City Delta inventory.Interestingly, a much better agreement is found for Moscow, with a range of 979-1249 Gg(CO)/yr194