Determinants of cities’ emissions: a comparison of seven global cities 3rd International Scientific Conference on “Energy and Climate Change” Athens 7th-8th October 2010 Edoardo Croci

Context Significant contribution of major cities to global GHG emissions, in particular of carbon dioxide (UNEP, UNHabitat, 2005: urban activities responsible for 80% of global CO2) Differences in urban absolute/per capita emissions among cities from industrialized and developing countries (and within each “category”) Increasing voluntary commitment of city governments to emissions reduction targets

Research questions - Which basic factors underlie urban emissions? - Which urban features interact in influencing these factors… …and can be considered as ultimate determinants of emissions?

Choice of case studies Criteria: focus on global cities (at least population > 1 million) availability of detailed emissions inventories availability of data on selected urban indicators representitiveness of different world areas (climate; economic performance) -> Bangkok, Chicago, London, Madrid, Mexico City, Milan, New York City Main bias: consistency of urban data used (methodology; territorial coverage) -> definitions of urban areas may differ among countries and accordingly to criteria used

Methodology -> Focus on residential emissions and ground transport Data availability Two main sectors in most of urban inventories Steps: 1) Disaggregation of emissions into main factors (emissions factors; activity data) 2) Analysis of emissions determinants qualitative comparison + quantitative indicators on urban features such as: climate, morphology, infrastructure, technology, economic activities in place, income, prices, culture…

Main factors: Built sector Eb = emissions from energy used in buildings   Qi = quantity of “i” fuel consumed directly for various purposes (i.e. heating, water heating, cooking...) for unit of built surface (kWh/m2) EFi = emission factor of “i” fuel (CO2/kWh) Si = floor space consuming “i” fuel (m2) f = 1, … 8 1 = natural gas 2 = oil 3 = LPG (Liquefied Petroleum Gas) 4 = coal 5 = waste used as fuel 6 = biomass 7 = energy from renewable sources 8 = other Qe = quantity of electricity consumed for various purposes (i.e. heating, water heating, cooking, air conditioning, use of electric appliances...) for unit of built surface (kWhe/m2) EFe = emission factor of electricity purchased in the city (CO2/kWhe) Se = floor space consuming electricity (m2)

Main factors: Built sector Residential sector: - significant differences in fuel and electricity consumption per housing unit (e.g. Chicago, highest values; Bangkok, Mexico City, lowest values) emissions factors have secondary relevance (apart from E.F. of electricity) Qi = fuel consumption (kWh/housing unit) Qe= electricity consumption (kWh/ housing unit) Qi Qe Qi+Qe Bangkok (2005) 1.194  4.657 5.851 Chicago 32.224 5.751 37.975 London (2003) 18.056 4.418 22.474 Madrid 8.766 3.249 12.015 Mexico City (2000) 4.369 1.391 5.759 Milan 15.275 2.375 17.649 New York City 14.283   6.319 20.602 EF. e.e. (gCO2/kWh) Bangkok 509 Chicago 664 London 430 Madrid 404 Mexico City 684 Milan 311 New York City

Main factors: Ground transport Where: Tj = number of passengers’ trips with “j” mode Lj = average length of a single trip with “j” mode (passengers km) lf = load factor of “j” mode (n. passengers/vehicle) EFji = emission factors of “i” fuel with “j” mode (gCO2/vehicle km) f = 1, … 6 1 = gasoline 2 = diesel 3 = LPG 4 = electricity 5= other 6 = no fuel VKTzi = kilometres travelled by freight vehicles of “i” fuel and of “z” mode (vehicle km/inhabitants) EFzi = emission factors of “i” fuel with “z” mode (gCO2/vehicle km) z = 1,…3 1 = light duty vehicles (and sub-categories) 2 = heavy duty vehicles (and sub-categories) 3 = rail m = 1, … 6 1 = foot 2 = bicycle 3 = subway/rail 4 = bus 5 = passenger car 6 = motorcycle

Tj (number of passengers trips per inhabitants per year) Main factors: Ground transport Ground transport: relevant role of private cars (Chicago) and freight (Chicago; Bangkok) in cities with higher emissions relevant role of non-motorized modes (New York City) and public transport (London; Madrid; Mexico City) in containing emissions Passengers transport Tj (number of passengers trips per inhabitants per year) Year Foot Bicycle Subway/rail Buses Pass. Cars Motorc. Bangkok 2005 14% - 3% 37% 46% Chicago 2001 5% 1% 6% 88% London 2003 21% 18% 16% 44% Madrid 26% 0,3% 22% 51% Mexico City* 2002 64% Milan 10% 19% 12% 50% New York City *For Mexico City data on foot/bicycle trips are not available

Main factors: Ground transport significant differences in the carbon intensity of the private and commercial vehicle stock e.g. Bangkok: very inefficient public and commercial fleet Chicago: carbon-intensive stock of passenger cars London, Milan: very low carbon intensity for passenger cars Year Buses (gCO2/km) Pass. Cars Bangkok 2005 - Chicago 579 London 2003 1200 176 Madrid Mexico City 2004 800 377 Milan 1398 212 New York City

Main determinants Built sector Residential emissions: climate, primary determinant: entails more relevant energy consumption levels for those cities having higher heating needs (e.g. Chicago, London, New York City) or cooling needs (Bangkok, as emerges from electricity consumption levels). Qi (kWh/ h.u.) HDD Chicago 32.224 3.610 London 18.056 2.679 New York City 14.283  2.641 Milan 15.275 2.157 Madrid 8.766 1.891 Mexico City 4.369 584 Bangkok 1.194  Qi = fuel consumption (kWh/housing unit) HDD= Heating Degree Days

Main determinants: Built sector - features of the residential stock: cities with a dense built environment consume lower energy quantities per housing unit better energy efficiency relevant in explaining lower energy consumption level - level of economic welfare: determinant for electricity use Qi+Qe Density (p/ha) New York City 20.602 104 Chicago 37.975 15 GDP p.c. (000$) Qe (kWh/h.u.) New York City 52,8 6.319 London 46,2 4.418 Madrid 29,0 3.249 Mexico City 14,3 1.391

Main determinants: Ground transport Ground transport emissions: form and density, primary determinant shaping modes in use and emissions: high density: relevant quota of passenger demand satisfied through non-motorized transport (New York City) and public transit (New York; London; Mexico City; Milan) lower density: significant use of private cars and higher emissions (e.g. Chicago) Car trips Foot Density (p/ha) Mexico City 236,1 n.a. 125 New York City 310,3 708,1 104 Milan 637,8 131,0 72 Madrid 508,4 255,5 56 London 554,0 272,0 55 Bangkok 313,8 95,5 36 Chicago 929,4 58,4 15

Main determinants: Ground transport Ground transport emissions: - technology and features of vehicle stock: determinant for cities where the stock is very inefficient (e.g. Bangkok) or very efficient (e.g. Milan). Average age of fleet (n. years) Emissions Transport (tCO2/per capita) buses passenger cars trucks Bangkok 3,74 14 (local) 7,5 (local) 12 (local) Milan 1,10 6,3 (local) 8,8 (national) 7,2 (local)

Future research need to collect more specific data at city level in order to support observations e.g. built sector: - typologies of housing units and commercial buildings - heating/cooling systems in operation within the city diffusion of electric appliances in households/offices and average energy efficiency e.g. ground transport: more detailed insight into the vehicle stock (private, public, commercial) data collection on specific urban features, in order to verify their link with the degree of use private cars/public transit (i.a. urban walkability; accessibility; integration of the public transport network) identify linkages between urban determinants of emissions and policies/measures evaluate trends of urban emissions through cities’ updates of emissions inventories