System dynamics life cycle-based carbon model for consumption changes in urban metabolism

Materials and energy consumed by urban systems are one of the main sources of greenhouse gas emissions. Measuring these flows and their associated emissions is necessary to estimate the impact of cities on climate change in the future. In this research we developed a dynamic model for measuring the carbon footprint of cities’ urban metabolism using an integrated socio-ecological systems approach. Illustrated with a case study in Montreal we modelled the urban carbon footprint between 2000 and 2018, and simulated on to 2030 under four scenarios: baseline, increasing adoption of plant-based diets (PBD), pavement/road material circularity (PMC), and a combined approach of the latter two. By simultaneously modelling Montreal's population growth the GHG per capita trend was compared to the anticipated 2030 global threshold of 2.9 t CO2e per person needed to meet the 1.5°C Paris Agreement target. All scenarios result in decreased per capita emissions from 15.0 t CO2e/capita in 2018, in part due to the increasing urban population. The baseline scenario estimates a decrease to 12.7 t CO2e by 2030; the PBD and PMC scenarios estimate respective reductions to 10.8 and 12.4 t CO2e/capita by 2030. The combined scenario estimates a greater reduction to 10.5 t CO2e/capita, but this is still 7.6 t CO2e/capita over the Paris Agreement target for 1.5°C global warming.