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Forces driving urban greenhouse gas emissions
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Forces driving urban greenhouse gas emissions David Dodman The contribution of urban areas to global greenhouse gas emissions has received substantial recent attention, in order both to allocate responsibility for climate change and to identify appropriate mitigation responses. The paper summarises these arguments, highlighting the challenges involved in creating an accurate and comparative measure of this. It shows how geography, urban form, and the urban economy influence the emissions from any given city. It then examines the use of ‘production’-based and ‘consumption’-based approaches for measuring emissions, and shows how particular lifestyles can be seen as the underlying drivers for manufacturing, food production, deforestation, and other activities that generate greenhouse gases. Address International Institute for Environment and Development, 3 Endsleigh Street, London WC1H 0DD, United Kingdom Corresponding author: Dodman, David ([email protected])
ant in the process of developing urban and global policies to respond to climate change. Firstly, benchmarking urban emissions is vital if targets for reducing these are to be meaningful and contribute to the necessary global mitigation efforts. Secondly, a globally comparable approach can form the basis for the development of carbon trading schemes that use the city as a unit of analysis, and that facilitate the transfer of low-carbon technology to cities in developing countries. This paper firstly summarises current mechanisms used to assess greenhouse gas emissions from urban areas, and reviews the findings from several attempts to provide accurate inventories. However, its primary focus is on the factors that shape city emission profiles, and the underlying drivers of these. It concludes by reviewing recent arguments that suggest meaningful long-term mitigation of climate change will require addressing patterns of consumption, particularly in middle-income and highincome countries.
Current Opinion in Environmental Sustainability 2011, 3:121–125 This review comes from a themed issue on Human Settlements and Industrial Systems Edited by Patricia Romero Lankao and David Dodman Received 5 October 2010; Accepted 26 December 2010 Available online 15th January 2011 1877-3435/$ – see front matter # 2010 Elsevier B.V. All rights reserved. DOI 10.1016/j.cosust.2010.12.013
Introduction The contribution of cities to global greenhouse gas emissions has become a hotly contested area of debate [1,2,3,4–6], as has the allocation of responsibility for climate change. The almost universal acceptance of the need to reduce atmospheric concentrations of greenhouse gases has lent these discussions particular importance as new mechanisms are sought to achieve this objective. Of course, a wide range of activities that take place in urban areas — including electricity generation, construction, manufacturing and service industries, and transportation — generate greenhouse gases. At the same time, towns and cities rely on inward flows of food, water, and consumer goods from elsewhere — whether rural areas, other urban areas, or overseas. Because of this, it is perhaps more appropriate to examine the underlying forces that drive greenhouse gas emissions — wherever the geographical location of their actual release. Measuring and understanding these forces is extremely importwww.sciencedirect.com
Assessing urban greenhouse gas emissions Climate change is caused by the increased atmospheric concentration of greenhouse gases, including carbon dioxide, nitrous oxide, methane, and ozone. The Intergovernmental Panel on Climate Change (IPCC) identifies energy supply, transportation, buildings, industry, agriculture, forestry, and waste and wastewater, as the main contributors to this process, and their relative contribution to global emissions is shown in Figure 1. The United Nations Framework Convention for Climate Change (UNFCCC) supervises the assessment of national greenhouse gas inventories, based on the assumption that a nation is responsible for all emissions produced within its area of jurisdiction. However, as many polluting and carbon-intensive manufacturing processes are no longer located in Europe or North America, but have been sited elsewhere in the world to take advantage of lower labour costs and less rigorous enforcement of environmental regulations, the underlying drivers of emissions are not adequately taken into account. For towns and cities, the responsibility for emissions is even less clear for two main reasons. Firstly, local government authorities have only very limited levels of control over emissions, lacking the legal powers to set targets or regulations on this issue. Secondly, a focus solely on the emissions emitted from within the identifiable territorial boundaries of an urban area is likely to misrepresent the responsibility for these emissions. In general, the smaller the scale, the greater the challenges posed by ‘boundary Current Opinion in Environmental Sustainability 2011, 3:121–125
122 Human Settlements and Industrial Systems
Figure 1
Waste and wastewater 3% Forestry 17%
Energy su supply 26%
Agriculture 14% Tr Transport 13%
Industry 19%
Buildings 8% Current Opinion in Environmental Sustainability
Anthropogenic greenhouse gas emissions by sector (2004) [7].
problems’ in which it is increasingly hard to identify which emissions ought or ought not to be allocated to a particular place [4]. At the most basic level, electricity generation often takes place outside urban administrative boundaries, yet is supplied to and consumed by industries, businesses, and households within the urban area. More complex relationships exist around the production of other goods and services outside towns and cities — including food production and transportation and the manufacture of many consumer goods — which are consumed in urban areas. However, although residents of cities in high-income countries are responsible for a very large share of greenhouse gas emissions, the increasing demand for energy (particularly household electricity) and private transportation in low-income and middleincome cities means that assessing and addressing the contribution of these urban centres to climate change will become increasingly important in the years to come. As a result of this, various frameworks have been proposed to enable cities to produce robust and comparable accounts of their contribution to climate change, including an ‘International Standard for Determining Greenhouse Gas Emissions for Cities’ produced by UNEP, UN Habitat, and the World Bank [8]. Other frameworks, such as the one developed by ICLEI Local Governments for Sustainability [9] identify urban emissions as coming either from ‘government operations’ or from ‘community activities’ (Table 1). Within each of these, emissions can be seen as belonging to several different ‘scopes’, depending on how directly their production is linked to a particular location. Scope 1 emisCurrent Opinion in Environmental Sustainability 2011, 3:121–125
sions represent direct emissions from within a given geographical area; Scope 2 emissions are those associated with electricity, heating, and cooling; and Scope 3 emissions include those that are indirect or embodied. In practice, greenhouse gas emission inventories from urban areas that include Scope 3 emissions are very rare — the point to which these Scope 3 emissions are included is very arbitrary and there is no agreement as to a comparable framework to compare emissions of this type between urban areas. If Scope 3 — or embodied — emissions are included, it is likely that the per capita emission of greenhouse gases allocated to a city will increase significantly — particularly if the city is large, well-developed and with a predominance of service and commercial activities [10]. In addition, it is almost impossible to compile a comprehensive inventory of Scope 3 emissions that takes into account all the consumption of all the individuals living in an urban area. In other words, ‘emissions can be attributed either to the spatial location of actual release or to the spatial location that generated activity that led to the actual release’ [11]. A detailed Scope 3 inventory should also subtract the embodied energy in goods made in that city and subsequently exported.
Factors influencing greenhouse gas emissions However, this process still only assesses the location of emissions, and not the underlying processes which drive these. These can be seen as either direct factors (related to geographic context, urban form and density, and economic activities) or underlying drivers (which requires a careful examination of the differences between ‘production’-based and ‘consumption’-based approaches to measuring greenhouse gas emissions). Various aspects of geography affect the contribution of urban areas to climate change. The geographical location of any given urban area affects energy demands for heating, cooling, and lighting. In the United States, areas with lower temperatures in January have higher emissions associated with home heating, while areas with warmer summers have higher electricity consumption associated with space cooling [12]. Geographical location also influences the fuels used for electricity generation, and hence the levels of greenhouse gas emissions from this process. Rio de Janeiro and Sa˜o Paulo in Brazil both have relatively low levels of emissions, as they receive a large proportion of their electricity from hydroelectric generation [13,14]; whereas many Chinese cities have high emissions associated with electricity generated by coal-fired plants [15]. Urban form and urban spatial organization can have a wide range of implications for a city’s greenhouse gas emissions [16]. The proximity of homes and businesses in dense urban areas can encourage walking, cycling and the use of mass transport in place of private motor vehicles www.sciencedirect.com
Forces driving urban greenhouse gas emissions Dodman 123
Table 1 Emission scopes for local authorities [9] Definitions Government operation emissions Scope 1 Direct emission sources owned or operated by the local government Scope 2 Indirect emission sources limited to electricity, district heating, steam, and cooling consumption Scope 3 All other indirect or embodied emissions over which the local government exerts significant control or influence Community-scale emissions Scope 1 All direct emission sources located within the geopolitical boundary of the local government Scope 2 Indirect emissions that result as a consequence of activity within the jurisdiction’s geopolitical boundary limited to electricity, district heating, steam and cooling consumption Scope 3 All other indirect and embodied emissions that occur as a result of activity within the geopolitical boundary
[17]. Some research suggests that the doubling of neighbourhood density can decrease per-household vehicle use by 20–40% (with a corresponding decline in greenhouse gas emissions ([18], p. 153), while an influential paper by Newman and Kenworthy [19] suggested that gasoline use per capita declines with increasing urban density. More compact housing also requires less energy for heating: US households living in single-family detached housing consume 35% more energy for heating and 21% more energy for cooling than comparable households in other forms of house [20]. Dense urban settlements can therefore be seen to enable lifestyles that reduce per capita greenhouse gas emissions through the concentration of services that reduces the need to travel large distances, the (generally) better provision of public transportation networks, and the constraints on the size of residential dwellings imposed by the scarcity and high cost of land. The types of economic activities that take place within urban areas also influence greenhouse gas emissions. Extractive activities and energy-intensive manufacturing are obviously associated with higher levels of emissions, especially when the energy for these is supplied from fossil fuels. The influence of the urban economy on patterns of emissions can be seen in the large variations in the proportion of a city’s greenhouse gas emissions that can be attributed to the industrial sector. Industrial activities were responsible for 80% of Shanghai’s emissions and 65% of Beijing’s (figures from 1999) [21]. In contrast, greenhouse gas emissions from the industrial sector in cities elsewhere are much lower, generally reflecting a transition to service-based urban economies: 0.04% in Washington, DC; 6.2% in Rio de Janeiro; 7% in www.sciencedirect.com
Examples A municipal vehicle powered by gasoline or a municipal generator powered by diesel fuel Purchased electricity used by the local government, which is associated with the generation of greenhouse gas emissions at a power plant Emissions resulting from contracted waste hauling services
Use of fuels such as heavy fuel oil, natural gas or propane used for heating Purchased electricity used within the geopolitical boundaries of the jurisdiction associated with the generation of greenhouse gases at the power plant
Methane emissions from solid waste generated within the community which decomposes at landfills either inside or outside of the community’s geopolitical boundary
London; 9.7% in Sa˜o Paulo; and 10% in Tokyo and New York City (figures collated in [2]).
Underlying drivers of emissions However, there are a range of underlying drivers that shape the amount of greenhouse gases emitted by a city. For example, in relation to emissions from manufacturing, Walker and King ([22], pp. 199–200) pose the question: ‘‘[M]any of the countries in the western world have dodged their own carbon dioxide emissions by exporting their manufacturing to. . . China. Next time you buy something with ‘Made in China’ stamped on it, ask yourself who was responsible for the emissions that created it.’’ The discussion above uses a ‘production-based’ approach to assess greenhouse gas emissions — based on the spatial location of the actual release of the gases. Yet this can lead to perverse and negative effects, as cities (or countries) create disincentives for activities that generate high levels of greenhouse gases, that merely result in these activities being moved to elsewhere in the world — a process referred to as carbon leakage [23]. In cities where service industries are more important, emissions associated with consumption are more important than those generated by production [24]. In contrast, a ‘consumption-based’ approach attempts to address the underlying drivers of emissions in a more complete way. This strategy attempts to identify a city or individual’s carbon footprint [see Romero-Lankao and Dodman, this issue] — the total set of greenhouse gases released by all Current Opinion in Environmental Sustainability 2011, 3:121–125
124 Human Settlements and Industrial Systems
the items consumed, wherever these emissions were produced geographically. These approaches have greater degrees of uncertainty, as there are many more systems to be incorporated, and there are high margins of uncertainty and a much higher potential for calculation error. Despite this, they provide considerable insight into climate policy and mitigation and should probably be used at least as a complementary indicator to help analyse and inform climate policy [25]. A consumption-based approach to industry, for example, would identify the driver of emissions to the final consumer of the products (many of whom live in wealth, service-oriented economies) rather than the enterprises that produce them (many of which are located in rapidly growing industrial economies such as India and China); and would allocate emissions from forestry and agriculture not to the rural areas (where they are produced) but rather to the consumers of these products (many or most of whom are in urban areas) [26]. Of course, global action is required to reduce the risks of climate change, yet the burden for meeting this goal should not fall on individuals or urban areas who have little responsibility for it [27]. A consumption-based analysis helps to ensure that the responsibility for addressing this problem lies with the individuals, urban areas and nations who have the greatest responsibility for causing it. Utilising a consumption-based approach has several implications. Firstly, in the case of many wealthy cities, it increases the greenhouse gas emissions for which the city and its residents are deemed to be responsible. Including Scope 3 emissions (as described above) in eight US city case studies led to an increase in per capita urban greenhouse gas emissions by an average of 45% [28]. In many cities in the developing world, the opposite situation is likely to be the case — for example, in the case of China, 33% of greenhouse gas emissions (equivalent to 6% of total global carbon emissions) in 2005 were identified as being due to production for export [29]. In addition, this perspective highlights the most important driver of urban greenhouse gas emissions as the process of consumption by urban residents. Social and cultural contexts also drive individual choices that affect emissions, including decisions about transportation modes and the ways in which energy is used in the home (switching off lights, managing heating and cooling, etc.). At the same time, however, it must be recognised that these choices are strongly shaped by the structural forces in the areas in which individuals live. For example, individuals living in urban area with effective integrated public transportation systems or safe, well-maintained bicycle pathways will be much more able to reduce distances travelled by car (as shown by Wright and Fulton [30], this can also be the case in low-income and middle-income countries). And among the factors leading to Tokyo’s relatively low per capita greenhouse gas emissions is its efficient urban infrastrucCurrent Opinion in Environmental Sustainability 2011, 3:121–125
ture, reliance on lower emitting sources of energy generation, and efficient end-use technology [10]. Policy responses to urban greenhouse gas emissions need to take into account both production and consumption approaches. Strategies to reduce emissions from within urban areas are more easily implementable and measurable. But if these rely on legislation and financial instruments that merely serve to encourage heavily emitting activities to move elsewhere — to places with less stringent regulations — then the net impact on global carbon emissions will be non-existent. On the other hand, strategies to promote responsible consumption are much more difficult to measure. Bridging these two issues will require urban and national authorities from both lowincome and high-income nations to work collaboratively with a range of stakeholders to develop innovative approaches: for example, through supporting the use of low-carbon technologies in manufacturing and service industries in low-income towns and cities as a development strategy.
Conclusion: addressing climate change mitigation in urban areas Assessing the sources of greenhouse gas emissions, or of the underlying drivers of these, is a purely academic exercise unless this information is used to develop effective, locally appropriate, strategies for climate change mitigation. Two general lessons can be drawn from this. Firstly, there is a need for more active engagement by city authorities in the processes of urban and global governance for climate change mitigation [31]. Local governments are able to shape the behaviour of citizens and industry through a combination of incentives and regulations, and thereby address the drivers of greenhouse gas emissions directly. Secondly, there is a need for deeper awareness and action by urban residents, particularly wealthy citizens of high-income countries. The consumption habits of these individuals acts to generate greenhouse gas emissions both directly (e.g. through emissions associated with transportation) and through the emissions embedded in the products they choose to buy (see [32] for a detailed analysis of the carbon footprint of many of these). When greenhouse gas emissions and climate change are seen in a global context, rather than simply as a matter of meeting targets at the urban or national level, then assessing and addressing these underlying drivers acquires true importance.
References and recommended reading Papers of particular interest, published within the period of review, have been highlighted as: of special interest of outstanding interest 1.
Bastianoni S, Pulselli F, Tiezzi E: The problem of assigning responsibility for greenhouse gas emissions. Ecol Econ 2004, 49:253-257. www.sciencedirect.com
Forces driving urban greenhouse gas emissions Dodman 125
2.
Dodman D: Blaming cities for climate change? An analysis of urban greenhouse gas emissions. Environ Urban 2009, 21:185-201. A meta-analysis of urban greenhouse gas emissions inventories, and a discussion of the underlying factors contributing to these.
3.
Hoornweg D, Sugar L, Gomez C: Cities and greenhouse gas emissions: moving forward. Environ Urban 2011, 23, in press. An up-to-date and comprehensive collection of data on urban greenhouse gas emissions, with description of mechanisms for assessing these, and discussion of policy implications.
4.
Kates R, Mayfield M, Torrie R, Witcher B: Methods for estimating greenhouse gases from local places. Local Environ 1998, 3:279-298.
5.
Kennedy C, Ramaswami A, Carney S, Dhakal S: Greenhouse gas emission baselines for global cities and metropolitan regions. Commissioned paper presented at World Bank Fifth Urban Research Symposium: 2009, June 28–30; 2009.
6.
Satterthwaite D: Cities’ contribution to global warming: notes on the allocation of greenhouse gas emissions. Environ Urban 2008, 20:539-549.
7.
Intergovernmental Panel on Climate Change (IPCC): Summary for policymakers. In Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Edited by Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt K, Tignor M, Miller H. Cambridge: Cambridge University Press; 2007.
8.
UNEP, UN Habitat and the World Bank: Draft International Standard for Determining Greenhouse Gas Emissions for Cities. 2010 . Available online http://www.unep.org/urban_environment/PDFs/ InternationalStd-GHG.pdf.
9.
ICLEI Local Governments for Sustainability: International Local Government GHG Emissions Analysis Protocol. Release Version 1.0. 2008:. Available online: http://www.iclei.org/fileadmin/ user_upload/documents/Global/Progams/GHG/ LGGHGEmissionsProtocol.pdf (accessed 29.07.09)..
10. Dhakal S: Climate change and cities: the making of a climate friendly future. In Urban Energy Transition: From Fossil Fuels to Renewable Power. Edited by Droege P. Elsevier Science; 2008: 173-192. 11. VandeWeghe J, Kennedy C: A spatial analysis of residential greenhouse gas emissions in the Toronoto Census Metropolitan area. J Ind Ecol 2007, 11:133-144 136–137. 12. Glaeser E, Kahn M: The greenness of cities: carbon dioxide emissions and urban development. Working Paper 2008-07. Harvard Kennedy School, Taubman Center for State and Local Government; 2008. 13. Dubeux C, La Rovere E: Local perspectives in the control of greenhouse gas emissions — the case of Rio de Janeiro. Cities 2007, 24:353-364. 14. Secretaria Municipal do Verde e do Meio Ambiente de Sa˜o Paulo (SVMA): Inventa´rio de Emisso˜es de Efeito Estufa do Municı´pio de Sa˜o Paulo. Centro de Estudos Integrados sobre Meio Ambiente e Mudanc¸as Clima´ticas (Centro Clima) da Coordenac¸a˜o dos Programas de Po´s-graduac¸a˜o de Engenharia (COPPE) da Universidade Federal do Rio de Janeiro (UFRJ); 2005. 15. Energy Information Administration: Official Energy Statistics from the US Government — Country Analysis Briefs; (n.d.). Available online: http://www.eia.doe.gov/emeu/cabs/index.html. 16. Dodman D: Urban form, greenhouse gas emissions and climate vulnerability. In Population Dynamics and Climate Change. Edited by Guzma´n J, Martine G, McGranahan G, Schensul D, Tacoli C. UNFPA/IIED; 2009.
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17. Satterthwaite D: The key issues and the works included. In The Earthscan Reader in Sustainable Cities. Edited by Satterthwaite D. London: Earthscan; 1999:3-21. 18. Gottdiener M, Budd L: Key Concepts in Urban Studies. London: Sage; 2005. 19. Newman P, Kenworthy J: Gasoline consumption and cities: a comparison of US cities with a global survey. J Am Plann Assoc 1989, 55:24-37. 20. Ewing R, Bartholomew K, Winkelman S, Walters J, Chen D: Growing Cooler: The Evidence on Urban Development and Climate Change Washington, DC: Urban Land Institute; 2008. 21. Gupta R, Chandiwala S: A critical and comparative evaluation of approaches and policies to measure, benchmark, reduce and manage CO2 emissions from energy use in the existing building stock of developed and rapidly-developing countries — case studies of UK, USA, and India. Commissioned paper presented at World Bank Fifth Urban Research Symposium: June 28–30 2009; Marseille; 2009. A detailed examination of energy use in buildings for three countries, including an assessment of how these are changing over time, and their implications for low-carbon development. 22. Walker G, King D: The Hot Topic: How to Tackle Global Warming .and Still Keep the Lights On London: Bloomsbury Publishing; 2008 23. Hertwich E, Peters G: Carbon footprint of nations: a global, trade-linked analysis. Environ Sci Technol 2009, 43:6414-6420. This study recognises that the ‘benefits’ of consumer goods and the ‘responsibility’ for the emissions generated by their manufacture are distributed unevenly, and argues that the importance of this has not yet been sufficiently appreciated in policy. 24. Bai X: Industrial ecology and the global impacts of cities. J Ind Ecol 2007, 11:1-6. 25. Peters G: From production-based to consumption-based national emission inventories. Ecol Econ 2007, 65:13-23. An explanation of production-based and consumption-based analysis for emissions inventories, and a discussion of potential options for incorporating consumption-based inventories into climate policy. 26. Satterthwaite D: The implications of population growth and urbanization for climate change. Environ Urban 2009, 21:545-567. 27. Adger W: Scales of governance and environmental justice for adaptation and mitigation of climate change. J Int Dev 2001, 13:921-931. 28. Ramaswami A, Hillman T, Janson B, Reiner M, Thomas G: A demand-centred, hybrid lifecycle methodology for city-scale greenhouse gas inventories. Environ Sci Technol 2008, 42:6455-6461. 29. Weber C, Peters G, Guan D, Hubacek K: The contribution of Chinese exports to climate change. Energy Policy 2008, 36:3572-3577. 30. Wright L, Fulton L: Climate change mitigation and transport in developing nations. Transport Rev 2005, 25:691-717. 31. Bulkeley H, Betsill M: Cities and Climate Change: Urban Sustainability and Global Environmental Governance Abingdon: Routledge; 2003. The most comprehensive assessment of the governance issues associated with managing urban greenhouse gas emissions, with detailed examples from several different countries. 32. Berners-Lee M: How Bad are Bananas? The Carbon Footprint of Everything. London: Profile Books; 2010.
Current Opinion in Environmental Sustainability 2011, 3:121–125
Forces driving urban greenhouse gas emissions David Dodman The contribution of urban areas to global greenhouse gas emissions has received substantial recent attention, in order both to allocate responsibility for climate change and to identify appropriate mitigation responses. The paper summarises these arguments, highlighting the challenges involved in creating an accurate and comparative measure of this. It shows how geography, urban form, and the urban economy influence the emissions from any given city. It then examines the use of ‘production’-based and ‘consumption’-based approaches for measuring emissions, and shows how particular lifestyles can be seen as the underlying drivers for manufacturing, food production, deforestation, and other activities that generate greenhouse gases. Address International Institute for Environment and Development, 3 Endsleigh Street, London WC1H 0DD, United Kingdom Corresponding author: Dodman, David ([email protected])
ant in the process of developing urban and global policies to respond to climate change. Firstly, benchmarking urban emissions is vital if targets for reducing these are to be meaningful and contribute to the necessary global mitigation efforts. Secondly, a globally comparable approach can form the basis for the development of carbon trading schemes that use the city as a unit of analysis, and that facilitate the transfer of low-carbon technology to cities in developing countries. This paper firstly summarises current mechanisms used to assess greenhouse gas emissions from urban areas, and reviews the findings from several attempts to provide accurate inventories. However, its primary focus is on the factors that shape city emission profiles, and the underlying drivers of these. It concludes by reviewing recent arguments that suggest meaningful long-term mitigation of climate change will require addressing patterns of consumption, particularly in middle-income and highincome countries.
Current Opinion in Environmental Sustainability 2011, 3:121–125 This review comes from a themed issue on Human Settlements and Industrial Systems Edited by Patricia Romero Lankao and David Dodman Received 5 October 2010; Accepted 26 December 2010 Available online 15th January 2011 1877-3435/$ – see front matter # 2010 Elsevier B.V. All rights reserved. DOI 10.1016/j.cosust.2010.12.013
Introduction The contribution of cities to global greenhouse gas emissions has become a hotly contested area of debate [1,2,3,4–6], as has the allocation of responsibility for climate change. The almost universal acceptance of the need to reduce atmospheric concentrations of greenhouse gases has lent these discussions particular importance as new mechanisms are sought to achieve this objective. Of course, a wide range of activities that take place in urban areas — including electricity generation, construction, manufacturing and service industries, and transportation — generate greenhouse gases. At the same time, towns and cities rely on inward flows of food, water, and consumer goods from elsewhere — whether rural areas, other urban areas, or overseas. Because of this, it is perhaps more appropriate to examine the underlying forces that drive greenhouse gas emissions — wherever the geographical location of their actual release. Measuring and understanding these forces is extremely importwww.sciencedirect.com
Assessing urban greenhouse gas emissions Climate change is caused by the increased atmospheric concentration of greenhouse gases, including carbon dioxide, nitrous oxide, methane, and ozone. The Intergovernmental Panel on Climate Change (IPCC) identifies energy supply, transportation, buildings, industry, agriculture, forestry, and waste and wastewater, as the main contributors to this process, and their relative contribution to global emissions is shown in Figure 1. The United Nations Framework Convention for Climate Change (UNFCCC) supervises the assessment of national greenhouse gas inventories, based on the assumption that a nation is responsible for all emissions produced within its area of jurisdiction. However, as many polluting and carbon-intensive manufacturing processes are no longer located in Europe or North America, but have been sited elsewhere in the world to take advantage of lower labour costs and less rigorous enforcement of environmental regulations, the underlying drivers of emissions are not adequately taken into account. For towns and cities, the responsibility for emissions is even less clear for two main reasons. Firstly, local government authorities have only very limited levels of control over emissions, lacking the legal powers to set targets or regulations on this issue. Secondly, a focus solely on the emissions emitted from within the identifiable territorial boundaries of an urban area is likely to misrepresent the responsibility for these emissions. In general, the smaller the scale, the greater the challenges posed by ‘boundary Current Opinion in Environmental Sustainability 2011, 3:121–125
122 Human Settlements and Industrial Systems
Figure 1
Waste and wastewater 3% Forestry 17%
Energy su supply 26%
Agriculture 14% Tr Transport 13%
Industry 19%
Buildings 8% Current Opinion in Environmental Sustainability
Anthropogenic greenhouse gas emissions by sector (2004) [7].
problems’ in which it is increasingly hard to identify which emissions ought or ought not to be allocated to a particular place [4]. At the most basic level, electricity generation often takes place outside urban administrative boundaries, yet is supplied to and consumed by industries, businesses, and households within the urban area. More complex relationships exist around the production of other goods and services outside towns and cities — including food production and transportation and the manufacture of many consumer goods — which are consumed in urban areas. However, although residents of cities in high-income countries are responsible for a very large share of greenhouse gas emissions, the increasing demand for energy (particularly household electricity) and private transportation in low-income and middleincome cities means that assessing and addressing the contribution of these urban centres to climate change will become increasingly important in the years to come. As a result of this, various frameworks have been proposed to enable cities to produce robust and comparable accounts of their contribution to climate change, including an ‘International Standard for Determining Greenhouse Gas Emissions for Cities’ produced by UNEP, UN Habitat, and the World Bank [8]. Other frameworks, such as the one developed by ICLEI Local Governments for Sustainability [9] identify urban emissions as coming either from ‘government operations’ or from ‘community activities’ (Table 1). Within each of these, emissions can be seen as belonging to several different ‘scopes’, depending on how directly their production is linked to a particular location. Scope 1 emisCurrent Opinion in Environmental Sustainability 2011, 3:121–125
sions represent direct emissions from within a given geographical area; Scope 2 emissions are those associated with electricity, heating, and cooling; and Scope 3 emissions include those that are indirect or embodied. In practice, greenhouse gas emission inventories from urban areas that include Scope 3 emissions are very rare — the point to which these Scope 3 emissions are included is very arbitrary and there is no agreement as to a comparable framework to compare emissions of this type between urban areas. If Scope 3 — or embodied — emissions are included, it is likely that the per capita emission of greenhouse gases allocated to a city will increase significantly — particularly if the city is large, well-developed and with a predominance of service and commercial activities [10]. In addition, it is almost impossible to compile a comprehensive inventory of Scope 3 emissions that takes into account all the consumption of all the individuals living in an urban area. In other words, ‘emissions can be attributed either to the spatial location of actual release or to the spatial location that generated activity that led to the actual release’ [11]. A detailed Scope 3 inventory should also subtract the embodied energy in goods made in that city and subsequently exported.
Factors influencing greenhouse gas emissions However, this process still only assesses the location of emissions, and not the underlying processes which drive these. These can be seen as either direct factors (related to geographic context, urban form and density, and economic activities) or underlying drivers (which requires a careful examination of the differences between ‘production’-based and ‘consumption’-based approaches to measuring greenhouse gas emissions). Various aspects of geography affect the contribution of urban areas to climate change. The geographical location of any given urban area affects energy demands for heating, cooling, and lighting. In the United States, areas with lower temperatures in January have higher emissions associated with home heating, while areas with warmer summers have higher electricity consumption associated with space cooling [12]. Geographical location also influences the fuels used for electricity generation, and hence the levels of greenhouse gas emissions from this process. Rio de Janeiro and Sa˜o Paulo in Brazil both have relatively low levels of emissions, as they receive a large proportion of their electricity from hydroelectric generation [13,14]; whereas many Chinese cities have high emissions associated with electricity generated by coal-fired plants [15]. Urban form and urban spatial organization can have a wide range of implications for a city’s greenhouse gas emissions [16]. The proximity of homes and businesses in dense urban areas can encourage walking, cycling and the use of mass transport in place of private motor vehicles www.sciencedirect.com
Forces driving urban greenhouse gas emissions Dodman 123
Table 1 Emission scopes for local authorities [9] Definitions Government operation emissions Scope 1 Direct emission sources owned or operated by the local government Scope 2 Indirect emission sources limited to electricity, district heating, steam, and cooling consumption Scope 3 All other indirect or embodied emissions over which the local government exerts significant control or influence Community-scale emissions Scope 1 All direct emission sources located within the geopolitical boundary of the local government Scope 2 Indirect emissions that result as a consequence of activity within the jurisdiction’s geopolitical boundary limited to electricity, district heating, steam and cooling consumption Scope 3 All other indirect and embodied emissions that occur as a result of activity within the geopolitical boundary
[17]. Some research suggests that the doubling of neighbourhood density can decrease per-household vehicle use by 20–40% (with a corresponding decline in greenhouse gas emissions ([18], p. 153), while an influential paper by Newman and Kenworthy [19] suggested that gasoline use per capita declines with increasing urban density. More compact housing also requires less energy for heating: US households living in single-family detached housing consume 35% more energy for heating and 21% more energy for cooling than comparable households in other forms of house [20]. Dense urban settlements can therefore be seen to enable lifestyles that reduce per capita greenhouse gas emissions through the concentration of services that reduces the need to travel large distances, the (generally) better provision of public transportation networks, and the constraints on the size of residential dwellings imposed by the scarcity and high cost of land. The types of economic activities that take place within urban areas also influence greenhouse gas emissions. Extractive activities and energy-intensive manufacturing are obviously associated with higher levels of emissions, especially when the energy for these is supplied from fossil fuels. The influence of the urban economy on patterns of emissions can be seen in the large variations in the proportion of a city’s greenhouse gas emissions that can be attributed to the industrial sector. Industrial activities were responsible for 80% of Shanghai’s emissions and 65% of Beijing’s (figures from 1999) [21]. In contrast, greenhouse gas emissions from the industrial sector in cities elsewhere are much lower, generally reflecting a transition to service-based urban economies: 0.04% in Washington, DC; 6.2% in Rio de Janeiro; 7% in www.sciencedirect.com
Examples A municipal vehicle powered by gasoline or a municipal generator powered by diesel fuel Purchased electricity used by the local government, which is associated with the generation of greenhouse gas emissions at a power plant Emissions resulting from contracted waste hauling services
Use of fuels such as heavy fuel oil, natural gas or propane used for heating Purchased electricity used within the geopolitical boundaries of the jurisdiction associated with the generation of greenhouse gases at the power plant
Methane emissions from solid waste generated within the community which decomposes at landfills either inside or outside of the community’s geopolitical boundary
London; 9.7% in Sa˜o Paulo; and 10% in Tokyo and New York City (figures collated in [2]).
Underlying drivers of emissions However, there are a range of underlying drivers that shape the amount of greenhouse gases emitted by a city. For example, in relation to emissions from manufacturing, Walker and King ([22], pp. 199–200) pose the question: ‘‘[M]any of the countries in the western world have dodged their own carbon dioxide emissions by exporting their manufacturing to. . . China. Next time you buy something with ‘Made in China’ stamped on it, ask yourself who was responsible for the emissions that created it.’’ The discussion above uses a ‘production-based’ approach to assess greenhouse gas emissions — based on the spatial location of the actual release of the gases. Yet this can lead to perverse and negative effects, as cities (or countries) create disincentives for activities that generate high levels of greenhouse gases, that merely result in these activities being moved to elsewhere in the world — a process referred to as carbon leakage [23]. In cities where service industries are more important, emissions associated with consumption are more important than those generated by production [24]. In contrast, a ‘consumption-based’ approach attempts to address the underlying drivers of emissions in a more complete way. This strategy attempts to identify a city or individual’s carbon footprint [see Romero-Lankao and Dodman, this issue] — the total set of greenhouse gases released by all Current Opinion in Environmental Sustainability 2011, 3:121–125
124 Human Settlements and Industrial Systems
the items consumed, wherever these emissions were produced geographically. These approaches have greater degrees of uncertainty, as there are many more systems to be incorporated, and there are high margins of uncertainty and a much higher potential for calculation error. Despite this, they provide considerable insight into climate policy and mitigation and should probably be used at least as a complementary indicator to help analyse and inform climate policy [25]. A consumption-based approach to industry, for example, would identify the driver of emissions to the final consumer of the products (many of whom live in wealth, service-oriented economies) rather than the enterprises that produce them (many of which are located in rapidly growing industrial economies such as India and China); and would allocate emissions from forestry and agriculture not to the rural areas (where they are produced) but rather to the consumers of these products (many or most of whom are in urban areas) [26]. Of course, global action is required to reduce the risks of climate change, yet the burden for meeting this goal should not fall on individuals or urban areas who have little responsibility for it [27]. A consumption-based analysis helps to ensure that the responsibility for addressing this problem lies with the individuals, urban areas and nations who have the greatest responsibility for causing it. Utilising a consumption-based approach has several implications. Firstly, in the case of many wealthy cities, it increases the greenhouse gas emissions for which the city and its residents are deemed to be responsible. Including Scope 3 emissions (as described above) in eight US city case studies led to an increase in per capita urban greenhouse gas emissions by an average of 45% [28]. In many cities in the developing world, the opposite situation is likely to be the case — for example, in the case of China, 33% of greenhouse gas emissions (equivalent to 6% of total global carbon emissions) in 2005 were identified as being due to production for export [29]. In addition, this perspective highlights the most important driver of urban greenhouse gas emissions as the process of consumption by urban residents. Social and cultural contexts also drive individual choices that affect emissions, including decisions about transportation modes and the ways in which energy is used in the home (switching off lights, managing heating and cooling, etc.). At the same time, however, it must be recognised that these choices are strongly shaped by the structural forces in the areas in which individuals live. For example, individuals living in urban area with effective integrated public transportation systems or safe, well-maintained bicycle pathways will be much more able to reduce distances travelled by car (as shown by Wright and Fulton [30], this can also be the case in low-income and middle-income countries). And among the factors leading to Tokyo’s relatively low per capita greenhouse gas emissions is its efficient urban infrastrucCurrent Opinion in Environmental Sustainability 2011, 3:121–125
ture, reliance on lower emitting sources of energy generation, and efficient end-use technology [10]. Policy responses to urban greenhouse gas emissions need to take into account both production and consumption approaches. Strategies to reduce emissions from within urban areas are more easily implementable and measurable. But if these rely on legislation and financial instruments that merely serve to encourage heavily emitting activities to move elsewhere — to places with less stringent regulations — then the net impact on global carbon emissions will be non-existent. On the other hand, strategies to promote responsible consumption are much more difficult to measure. Bridging these two issues will require urban and national authorities from both lowincome and high-income nations to work collaboratively with a range of stakeholders to develop innovative approaches: for example, through supporting the use of low-carbon technologies in manufacturing and service industries in low-income towns and cities as a development strategy.
Conclusion: addressing climate change mitigation in urban areas Assessing the sources of greenhouse gas emissions, or of the underlying drivers of these, is a purely academic exercise unless this information is used to develop effective, locally appropriate, strategies for climate change mitigation. Two general lessons can be drawn from this. Firstly, there is a need for more active engagement by city authorities in the processes of urban and global governance for climate change mitigation [31]. Local governments are able to shape the behaviour of citizens and industry through a combination of incentives and regulations, and thereby address the drivers of greenhouse gas emissions directly. Secondly, there is a need for deeper awareness and action by urban residents, particularly wealthy citizens of high-income countries. The consumption habits of these individuals acts to generate greenhouse gas emissions both directly (e.g. through emissions associated with transportation) and through the emissions embedded in the products they choose to buy (see [32] for a detailed analysis of the carbon footprint of many of these). When greenhouse gas emissions and climate change are seen in a global context, rather than simply as a matter of meeting targets at the urban or national level, then assessing and addressing these underlying drivers acquires true importance.
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