Tracking the consumption-based CO2 emissions of typical Chinese megacities in multiscale economies

Accurately tracking consumption-based CO2 emissions of megacities is crucial for clarifying regional mitigation responsibility. However, without a general emission framework, it's challenging to accomplish comparative studies of multi-megacities by quantitative carbon flow analyses. Here, we constructed a megacity-centred multilevel emission accounting framework and developed a methodology based on the revised multiscale multi-regional input-output model. Our approach integrates in-boundary and trans-boundary carbon flow driven by final demand and thus constructs urban classifications based on self-constructed consumption degree. The results indicate heterogeneity and commonality of megacities' consumption-based emissions in spatial and industrial distribution. Trans-boundary consumption-based emissions account for 81%–93% of the total in megacities, mainly from mainland China. While the majority of megacities are net importers overall, for relatively developed regions, megacities with low consumption degrees remain net exporters. At sector-level, 3 key sectors of other manufacturing, construction and services drive more than 75% of emissions. Inspired by the results, we propose differentiated carbon governance implications based on urban emission pattern classification, exploring priorities for emission reduction. Our research indicated the need for megacities as pioneers to consider consumption-side emission reductions.