City-scale carbon footprint accounting and mitigation analysis

Abstract

Cities accommodate more than half of the global population, consume 70% of global energy and are responsible for 80% of global greenhouse gas (GHG) emissions, and thus play a crucial role in climate change mitigation. Global cities are linked together through international trade and join forces against climate change through global networks. However, the lack of multi-scale city carbon footprint (CF) accounting has hampered mitigation policies that tackle transboundary emissions and relate to economic sectors across different scales. This thesis addresses the topic of cities and climate change from the viewpoint of one overarching aim: To develop and apply comprehensive city CF frameworks that can inform low-carbon urban development across multiple scales based on city-scale multiregional input-output (MRIO) analysis. In order to create an improved urban CF accounting method (Research Question 1), this thesis introduces a ‘city carbon map’ concept which shows all origins and destinations of embodied emissions. Research Question 2 then addresses how the complexity of interconnections between cities and their hinterlands can be assessed in terms of embodied emissions. As a case study, sectors and regions located upstream or downstream of urban supply chains are assessed for Australian and Chinese cities to facilitate implementation of specific, effective and efficient decarbonisation policies. Finally, the thesis extends the research scope to suburban-scale and models suburb-specific carbon intensity accounting for the heterogeneity of both production and consumption in different suburbs. This has addressed Research Question 3 on how suburb-scale household carbon footprints can inform spatial urban planning debates. In summary, this thesis provides a comprehensive city-scale CF framework to facilitate the implementation of mitigation policies across different scales. For the first time a consumption-based accounting method is proposed that combines the three scopes of standard emissions accounting. The city CF networks model introduced allows assessing the emissions embodied in trade between cities within and across nations. The application of spatial and sectoral linkage analysis helps to identify key sectors for urban carbon transformation. The thesis also makes the first attempt in suburban CF accounting and contributes to the debate on carbon footprints and urban density from a sectoral perspective.