Large Suburban Carbon Footprints Negate GHG Benefits of Urban Areas

by Dan McCabe

Jones and Kammen (2014) performed a remarkably thorough analysis of the average household carbon footprint (HCF) for nearly every US zip code and examined how dozens of different variables affect greenhouse gas (GHG) emissions. The authors’ analysis used detailed data from the nationwide Residential Energy Consumption Survey, the National Household Travel Survey, and other sources. Their model used these surveys to estimate local emissions due to components such as electricity, housing, transportation, and food, then evaluated possible correlations with 37 independent demographic variables. Continue reading

Intelligent Planning Can Offset Much of Projected Energy Demand Increases

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. Continue reading

Models Reveal Climatic Impacts of Urban Expansion

by Dan McCabe

Greenhouse gases have earned a bad name for their impacts on global climate, but in modern cities, the built environment itself can contribute to climate change just as much. In order to quantify and analyze the impacts of urbanization on local and regional temperature and hydroclimate, Georgescu et. al. (2014) modeled the impacts of urban expansion in the contiguous United States in a variety of scenarios. The authors considered a range of different predicted population levels in the United States for the year 2100. Using advanced atmospheric models, they found that if no urban climate change mitigation measures were put into place by then, summertime urban-induced warming of 1–3 °C can be expected in cities, with exact values varying by location. These increased temperatures are due solely to the effects of the built environment, as simulations were run using climate data from 2001-2008 without any assumptions about future warming due to increased greenhouse gas emissions. Continue reading