by Dan McCabe
Urban areas account for the majority of global energy consumption and greenhouse gas emissions, which is of growing concern as their populations are projected to double within the next 35 years. In order to inform urban planning efforts to reduce greenhouse gas emissions, Creutzig et al. (2015) studied how a wide array of variables influence the energy consumption of cities across the globe. The authors considered detailed data provided by the World Bank (WB), the Global Energy Assessment (GEA), and the International Association of Public Transport (UITP) for 274 different-sized cities from 60 different countries. A correlation analysis was performed to determine how significant an impact each variable—such as gasoline price, population density, and gross domestic product (GDP)—appeared to have on citywide energy consumption. The dependent variable for this analysis depended on the data set from which information was obtained: per capita energy use for the GEA data, per capita transportation energy use for the UITP data, and per capita greenhouse gas emissions for the WB data. A standard linear regression model was used to determine the significance of each independent variable.
The results of the analysis depend on the data set and corresponding dependent variable considered. GHG emissions and transport energy consumption are most strongly correlated with gasoline prices and population density. Total energy consumption, however, is most effected by urban economic activity and climate, measured in heating degree days. The influence of each possible variable, however, differs across the range of cities studied.
An understanding of the important factors that contribute to urban energy demand allowed the researchers to assess the potential to reduce consumption. With global urban populations expected to double by 2050, cities are an important target for decreasing overall emissions. The authors found that strategic urban planning and the ideal implementation of fuel taxes could reduce projected urban energy consumption in 2050 from about 730 EJ in the business-as-usual scenario to 540 EJ, with most of the difference coming in the developing regions of Asia, Africa, and the Middle East.
While the analysis in this paper does not perfectly explain the energy usage of vastly different urban areas and projections for the future always carry substantial uncertainties, it makes some highly valuable contributions to understanding how cities can be more sustainable. Specifically, the energy demand of cities in the coming decades can be reduced by promoting high population density and, when possible, higher fuel prices. Specific planning strategies should be customized for different areas according to their needs; for example, fuel taxes are more effective in relatively affluent locations. While there does not appear to be a way to prevent consumption from rising severely as global population grows, this research offers pragmatic, useful data to encourage cities to develop with as little impact as possible.
Creutzig, F., Baiocchi, G., Bierkandt, R., Pichler, P., Seto, K. C., 2015. Global typology of urban energy use and potentials for an urbanization mitigation wedge. Proceedings of the National Academy of Sciences, published ahead of print. http://www.pnas.org/content/early/2015/01/07/1315545112.full.pdf