Recent research quantifying anthropogenic CO₂ emissions at the street scale within the urban domain

This paper provides a review of the need, challenges and recent research aimed at quantifying anthropogenic CO₂ emissions for urban areas at spatial scales below the whole city, and sub-annual temporal scales. With whole-city CO₂ emissions budget research as a starting point, suburban efforts must first clearly identify the accounting framework, sectoral boundaries, chemical form, spatial domain and the space/time resolution desired. The only efforts, to date, have performed analysis in a few North American cities utilizing a combination of true "bottom-up" and space/time downscaling techniques. Numerous challenges are faced when estimating CO₂ emissions at these scales, including data availability, data idiosyncrasy and uncertainty quantification. Though cities in high-income countries are in possession of the needed data, data availability may pose far greater difficulties in other parts of the world. Because much of the data that is available does not possess uncertainty estimates, quantification of CO₂ emissions uncertainty similarly remains a large challenge. Suggested solutions include sensitivity testing of key inputs and parameters, fully propagated through estimation systems. To overcome data availability challenges, the exploration of high-resolution remote-sensing data offers insight into urban activity.