The role of cities and their stakeholders in creating a sustainable low carbon society is becoming increasingly critical. Cities and their supply chains are responsible for almost 80% of the global energy consumption and over 60% of greenhouse gas emissions (GHG). It is expected that 70% of the global population will be living in urban areas by 2050. However, in general cities still quantify and report only their production-based GHG emissions and fail to account for their supply chains. There has been much less focus on the GHG emissions associated with consumption in cities, including household and government consumption.
This paper compares the production-based GHG accounting method with the consumption-based method for ten European cities. This is performed for a base year (2010) and two divergent future scenarios for 2050, a business-as-usual (BAU) scenario and a post carbon (PC 2050) scenario. The PC2050 scenario was created by city stakeholders in the framework of the European research project POCACITO in (2014–2016). Consumption-based emissions are calculated using the EXIOBASE multi-regional input-output model.
Compared to 2010, both BAU and PC2050 scenarios show significant decreases for production-based emissions, falling 31% and 68% respectively. However, during this period consumption-based emissions increase for eight cities, rising 33% and 35% respectively. This occurs despite the modelled improvements in global production efficiency for 2050 and the significant production-based reductions under the PC2050 scenarios. The increase in consumption-based emissions is primarily linked to rising GDP and a corresponding increase in spending and consumption, which override the local and global efficiency improvements.
Hence the results highlight a notable disparity between the traditional focus on production-based accounting and consumption-based accounting. This suggests that future city actions should extend their focus on addressing the impact of consumption in addition to local energy production and emissions. It also suggests that city stakeholders are generally underestimating the impact of consumption and the responses required.