Exploring the interplay of multiple greenhouse gas emissions drivers at the city level

The factors that influence emissions of greenhouse gasses in cities are multifarious. Researchers have documented that population and economic growth are primary drivers of emissions in urban areas (Brown et al., 2008; Romero Lankao et al., 2009). In addition, others have cited the emissions intensity of an urban area's energy source is a fundamental cause for variation of environmental impact across cities (Grubel, 2004). By contrast, factors that are associated with lower GHG emissions in metropolitan areas include urban form (often measured as population density) and the modal share of alternative transportation used (Kenworthy, 2008; Romero Lankao et al., 2009; Dodman 2009). We will present the results of a study that statistically employs proxies for each of these factors to empirically ascertain whether the interplay between population, economy, emissions intensity, population density, and use of alternative transportation has an effect on CO ₂ emissions in a set of 51 cities.