<b>Gurney</b>, K. R., P. <b>Romero-Lankao</b>, S. <b>Pincetl</b>, M. Betsill, M. Chester, F. Creutzig, K. Davis, R. Duren, G. Franco, S. Hughes, L. R. Hutyra, C. Kennedy, R. Krueger, P. J. Marcotullio, D. Pataki, D. Sailor, and K. V. R. Schäfer, 2018: Chapter 4: Understanding urban carbon fluxes. In Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report [Cavallaro, N., G. Shrestha, R. Birdsey, M. A. Mayes, R. G. Najjar, S. C. Reed, P. Romero-Lankao, and Z. Zhu (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 189-228, https://doi.org/10.7930/SOCCR2.2018.Ch4.
Understanding Urban Carbon Fluxes
4.5.1 Global Urban Carbon
Of the nearly 1,000 urban agglomerations with more than 500,000 people across the world, three-quarters are in developing countries (UN DESA 2015). The share of energy-related urban CO2 emissions worldwide is 71%, somewhat less than the share in North America (IEA 2008). Given the greater levels of current urbanization in North America and recent trends across the world, most future urban growth and associated urban carbon emissions likely will be dominated by low- and middle-income countries. In smaller urban areas within the United States and Europe, de-urbanization is occurring (Martinez-Fernandez et al., 2012), and its implications for carbon emissions are still poorly understood.
Within the global context, North America (particularly Canada and the United States) has smaller urban population densities but greater per capita built-up area (Seto et al., 2014). Due to extensive urbanization levels and fossil fuel consumption associated with transportation and urban infrastructure, North America has the largest percent of total carbon emissions emanating from urban areas (Marcotullio et al., 2013).
4.5.2 United States, Canada, and Mexico—Urban Carbon in Context
Cities in the United States and Canada generally have recorded amongst the highest per capita carbon emissions when compared to global cities (Dodman 2009; Hoornweg et al., 2011; Kennedy et al., 2009; Sovacool and Brown 2010). In cities for which there are repeat carbon inventories (e.g., Boston, New York City, Toronto, and Seattle, from 2004 to 2009), per capita emissions are declining at the same rate as national inventories (Kennedy et al., 2012). But when indirect emissions are included in city inventories, urban per capita emissions are about the same as national per capita emissions (Ramaswami et al., 2008). This measurement further highlights the importance of understanding indirect carbon fluxes and the increase in the export of emissions outside the North American urban domain. Core aspects of per capita energy and material consumption have been found to be inversely correlated to urban population density (Kennedy et al., 2015).
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