Urban environments and trans-boundary linkages

Urban areas have become increasingly important for addressing carbon mitigation because of their significant contribution to global anthropogenic carbon emissions. Cities have been exploring effective actions to reduce their carbon impacts. These urban climate policies include addressing demand reduction (e.g., behavior nudges, and travel demand reduction) and reducing supply-side carbon impacts (e.g., waste-to-energy and local renewable energy adoption). During the past decade, the science of urban carbon accounting has advanced in response to these policy considerations. Four broad carbon accounting approaches (i.e., purely territorial carbon accounting, community-wide transboundary infrastructural supply chain carbon accounting, consumption-based carbon accounting, and total community-wide carbon accounting) have emerged at the city scale. This chapter summarizes the differences and overlaps of these accounting approaches, including their policy relevance and benchmarking metrics. It then discusses the value that each approach offers to urban climate policies, which has not been explained in previous literature. We emphasize that each approach is complete for its designed purposes and is valuable for different stakeholders (e.g., homes, businesses, industry, local government, etc.). In addition to explaining the value of four urban carbon approaches to individual cities, we discuss emerging efforts that quantify biogenic carbon from urban areas and account for all urban areas’ carbon emissions in a nation. This chapter provides a roadmap for urban policymakers choosing appropriate accounting approaches.