World Bank and U of T researchers find suburbs emit more greenhouse gases than inner cities
Thursday, May 12, 2011 10:33:00 AM
Daniel Hoornweg, Lorraine Sugar, Claudia Lorena Trejos Gómez. "Cities and greenhouse gas emissions: moving forward". Environment and Urbanization, April 2011; vol. 23, no 1: 207-227.
Cities are blamed for the majority of greenhouse gas (GHG) emissions. So too are more affluent, highly urbanized countries. However, this study reveals that residents of denser city centres can emit half the GHG emissions of their suburban neighbours. For example, when comparing three Greater Toronto Area neighbourhoods, Whitby had the highest GHG emissions per capita of 13.02 tCO2e (tonnes of CO2 equivalent) attributed to its large, low-density single family homes and long distance from commercial activity. Etobicoke had 6.62 tonnes and East York had the lowest (1.31 tonnes), attributed to its higher density homes and apartment complexes within walking distance of shopping and public transit.
This paper presents a detailed analysis of per capita GHG emissions for several large cities and a review of per capita emissions for 100 cities for which peer-reviewed studies are available. The researchers used 2001 data which were also part of a 2007 study by U of T Civil Engineering Professor Chris Kennedy and then B.A.Sc. student Jared VandeWeghe, analyzing residential greenhouse gas emissions in the Toronto census metropolitan area. ("A spatial analysis of residential greenhouse gas emissions in the Toronto census metropolitan area", Journal of Industrial Ecology. vol 11, no 2: 133-144.)
The paper also highlights how average per capita GHG emissions for cities vary from more than 15 tCO2e (Sydney, Calgary, Stuttgart and several major US cities) to less than half a tonne (various cities in Nepal, India and Bangladesh). The paper discusses where GHG emissions arise and where mitigation efforts may be most effective. It illustrates the need to obtain comparable estimates at city level and the importance of defining the scope of the analysis. Emissions for Toronto are presented at a neighbourhood level, city core level and metropolitan area level, and these are compared with provincial and national per capita totals. This shows that GHG emissions can vary noticeably for the same resident of a city or country depending on whether these are production- or consumption-based values.
This is an edited excerpt from the article found free online (for U of T community) at
Daniel Hoornweg is a Lead Urban Specialist, World Bank, Washington DC.
Lorraine Sugar is a recent M.A.Sc. graduate (November 2010), Dept. of Civil Engineering, University of Toronto.
Claudia Lorena Trejos Gómez is Consultant Urban and Regional Planner, World Bank, Washington DC.