City module - Urban GHG emission database




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Cities are the place where most people live, yet it is still a matter of debate what portion of current GHG emissions is associated to urban areas. Numbers vary from 30% to 80%, depending on the methodology and whether production or consumption-based emissions are accounted for (Hoornweg et al, 2011).

In any event, the building blocks for these calculations are commonly urban GHG inventories, i.e. case by case inventories of the amount of GHGs a city is responsible for. The total and per capita values largely diverge because they depend on a number of city specific factors that make cities across the globe so heterogeneous, and on further methodology-specific factors. These factors include inter alia: a) the sectoral focus of the inventory b) the methodology used c) rigor in accounting d) energy production e) industrial and commercial fabric of a city f) affluence and lifestyle.

This module provides an introduction to these differences by using a a selection of urban GHG emission inventories published in peer reviewed journals or reports from research institutes and non-governmental organizations (Table 1). The per capita emissions considered range from 0.1 t/cap for Rajshahi, Bangladesh ICLEI (2009) and 43.7 t/cap for Aberystwyth, Wales (derived from Dore et al. (2006) and Carbon Trust (2007).

Explore the datasets by using the extensive visualization options: Adjust the variables used for the y-axis, x-axis, size, and color of the bubbles chart to your needs.

Table 1: Selection of published urban GHG emission datasets, the types of emissions considered, and methods employed.

Source Number of cities Spatial distribution Emission types considered Method
Brown et al, 2008 99 USA Transportation (without shipping and aviation), Energy Use (Residential) national databases (passenger and freight transportation, residential energy consumption)
Dore et al, 2006 31 UK Transportation (without shipping and aviation), Energy Use (Residential), Industry (Commercial Energy Use), AFOLUiculture, Forestry and other land use, Aviation and/or marine sources (shipping) NAEI UK (emission factor*human activity and reported point source emissions)
Carney et al, 2009 17 Europe Energy Use (Residential), Industry (Commercial Energy Use), Waste, Agriculture, Forestry and other land use (AFOLU) GRIP Europe
Dhakal, 2009 3 China Energy Use (Residential) energy use*emission factors of fuel types
ICLEI, 2009 53 Asia Transportation (without shipping and aviation), Energy Use (Residential), Industry (Commercial Energy Use), Waste HEAT (Harmonised Emissions Analysis Tool)
Kennedy et al, 2009 10 Global Energy Use (Residential), Industry (Commercial Energy Use), Transportation (without shipping and aviation), (AFOLU), Waste, Aviation and/or marine sources (shipping) Not specified
Sovacool and Brown, 2010 9 Global Transportation (without shipping and aviation), Energy Use (Residential), Industry (Commercial Energy Use), AFOLU, Forestry and other land use, Waste calculation based on previously published literature


Important messages of the study

Using the charts application quickly shows the breadth of per capita values. For example, the ICLEI dataset indicates how cities in the same country (India) diverge by factor 100 - despite using the same method.

In addition, this small selection of published studies indicates the lack of studies for cities in less and least developed countries - a gap that is challenging yet important to fill in order to get a global overview of how cities GHG emissions relate to factors such as wealth, density, size, population, and their economies.

It is crucial to understand which city datasets are comparable, and which are not. In this module, only city inventories originating from the same study can be compared, while city inventories originating from different studies can not.

What are assumptions and other reasons that limit the use of the results?

A proposal for a principal standard for urban emission inventories has recently been suggested by a number of authoritative institutions on the matter. However, for currently existing inventories a multitude of methodologies have been and are still in use, ranging widely in terms of the area, sector or emission(s) of interest, the precision of the methodologies applied, and in how far the inventories abided by the methodology and traceably documented the input, methods and findings in the published results. The literature and its urban emissions figures considered for this study reflect this heterogeneity, which are a source of dispersion.

How was the data prepared/analysis performed?

CO2e emission figures were retrieved from collections of urban GHG emission inventories published in peer reviewed journals or reports from research institutes and non-governmental organizations. Published figures were largely drawn from primary sources such as city inventories covering emissions in their territories. If necessary, figures were traced back to their original publication source for verification.

References

Brown, M.A., Southworth, A., Sarzynski, A. (2008): Shrinking the Carbon Footprint of Metropolitan America. Brookings Institute Metropolitan Policy Program, Washington D.C.

Carbon Map of the UK (2007), Data Sheet - http://www.carbontrust.co.uk/news/news/press-centre/2007/Pages/010607_Carbon_map.aspx; Data extracted from: Dore, C.J. et al. (2006): UK Emissions of Air Pollutants 1970 to 2005. - http://naei.defra.gov.uk/reports.php.

Carney, S., Green, N., Wood, R., Read, R. (2009): Greenhouse Gas Emissions Inventories for Eighteen European Regions, EU CO2 80/50 Project Stage 1: Inventory Formation. The Greenhouse Gas Regional Inventory Protocol (GRIP).

Dhakal, S. (2009): Urban energy use and carbon emissions from cities in China and policy implications, Energy Policy; doi:10.1016/j.enpol.2009.05.020.

Hoornweg, D., Sugar, L., Gomez, C. L. T., 2011. Cities and greenhouse gas emissions: moving forward. Environ. Urban. 23 (1), 207-227.

ICLEI-South Asia: Local Governments for Sustainability (2009): Energy and Carbon Emissions Profiles of 54 South Asian Cities. New Delhi.

Kennedy, C.A., Steinberger, J. et al. (2009a): Greenhouse Gas Emissions from Global Cities. Environ. Sci. Technol. 2009, 43, 7297-7302 - http://pubs.acs.org/doi/pdf/10.1021/es900213p.

Sovacool, B.K., Brown, M.A. (2010): Twelve metropolitan carbon footprints: A preliminary comparative global assessment. Energy Policy 38, pp. 4856-4869.