Factor decomposition analysis of urban transport CO2 emissions in Chinese mega cities: case study of Beijing, Shanghai, Guangzhou and Shenzhen

With the progress of urbanization, more activities and CO(2 )are concentrated in urban, and transport sector becomes one of the most important sources of carbon emissions in cities. With the quick growth of urban transport activities, to achieve China's carbon emission peaking and neutrality target, controlling urban transport CO2 emissions becomes more important and difficult. Current studies lack a full-chain analysis of the impact of urban structure, modal share, technical level, and operational level on carbon emissions, especially the lack of analysis of rapidly urbanizing, motorizing, and electrifying in Chinese cities. To fill this gap, this paper conducts a decomposition and causal analysis of the urban transport sector in four Chinese megacities, Beijing, Shanghai, Shenzhen and Guangzhou. Base on the full chain analysis, urbanization, motorization, and technology level are the main factors influencing the growth of carbon emissions from passenger transport in the four cities. In the early stage of urban development, urbanization is responsible for the growth of carbon emissions; in the later stage of urban development, motorization is mainly responsible for the growth of carbon emissions; and in the future, technology level is the key to reducing emissions. Specifically, because of the COVID-19 epidemic, trip rates in the four cities drop significantly and make a noticeable change in CO2 emissions. Besides, it is found by the full chain analysis that the different focus on the three factors (urbanization, motorization, technological level) ultimately led to the difference in the change of carbon dioxide emissions in the four cities.