Progressive cities worldwide have demonstrated political leadership by initiating meaningful strategies and actions to tackle climate change. However, the lack of knowledge concerning embodied greenhouse gas (GHG) emissions of cities has hampered effective mitigation.
A trans-national, multi-region input-output analysis for cities is presented.
The authors examine the carbon footprint network of ten cities.
The balance of emissions embodied in trade discloses a hierarchy of responsibility.
The authors model how emissions reductions spread through the city carbon networks.
As global population and urbanization increase, so do the direct and indirect environmental impacts of construction around the world. Low-impact products, buildings, precincts and cities are needed to mitigate the effects of building construction and use. Analysis of embodied energy and greenhouse gas (GHG) emissions across these scales is becoming more important to support this direction.
Suburbs have naturally become a focal point of carbon mitigation for cities undergoing rapid suburbanization. This has created a debate over which urban form can more effectively lead to lower household carbon footprints (CF). Previous suburban-scale studies using economic input-output life cycle assessment with national average carbon intensities have demonstrated the mitigation potentials in households via urban planning.
With around 80% of global greenhouse gas emissions directly or indirectly attributed to cities, attempts to mitigate climate change impacts must seriously consider urban carbon transformations. Two challenges are currently constraining urban planning decisions around decarbonisation. Firstly, a lack of detailed knowledge about city-induced emissions occurring outside of the city boundary hampers the design of mitigation strategies that involves the city's ‘hinterland’.
Cities are thought to be associated with most of humanity's consumption of natural resources and impacts on the environment. Cities not only constitute major centers of economic activity, knowledge, innovation, and governance—they are also said to be linked to approximately 70% to 80% of global carbon dioxide emissions. This makes cities primary agents of change in a resource- and carbon-constraint world. In order to set meaningful targets, design successful policies, and implement effective mitigation strategies, it is important that greenhouse gas (GHG) emissions accounting for cities is accurate, comparable, comprehensive, and complete. Despite recent developments in the standardization of city GHG accounting, there is still a lack of consistent guidelines regarding out-of-boundary emissions, thus hampering efforts to identify mitigation priorities and responsibilities. We introduce a new conceptual framework—based on environmental input-output analysis—that allows for a consistent and complete reconciliation of direct and indirect GHG emissions from a city. The “city carbon map” shows local, regional, national, and global origins and destinations of flows of embodied emissions. We test the carbon map concept by applying it to the greater metropolitan area of Melbourne, Australia. We discuss the results and limitations of the approach in the light of possible mitigation strategies and policies by different urban stakeholders.