CO₂ emissions caused by household consumption have become one of the main sources of greenhouse gas emissions. Studying household CO₂ emissions (HCEs) is of great significance to energy conservation and emissions reduction. In this study, we quantitatively analyzed the direct and indirect CO₂ emissions by urban and rural households in Beijing, Tianjin, Shanghai, and Chongqing. The results show that urban total HCEs are larger than rural total HCEs for the four megacities. Urban total per capita household CO₂ emissions (PHCEs) are larger than rural total PHCEs in Beijing, Tianjin, and Chongqing, while rural total PHCEs in Shanghai are larger than urban total PHCEs. Electricity and hot water production and supply was the largest contributor of indirect HCEs for both rural and urban households. Beijing, Tianjin, Shanghai, and Chongqing outsourced a large amount of indirect CO₂ emissions to their neighboring provinces.

CO₂ and SO_2, while having different environmental impacts, are both linked to the burning of fossil fuels. Research on joint patterns of CO₂ emissions and SO₂ emissions may provide useful information for decision-makers to reduce these emissions effectively. This study analyzes both CO₂ emissions and SO₂ emissions embodied in interprovincial trade in 2007 and 2010 using multi-regional input–output analysis. Backward and forward linkage analysis shows that Production and Supply of Electric Power and Steam, Non-metal Mineral Products, and Metal Smelting and Pressing are key sectors for mitigating SO₂ and CO₂ emissions along the national supply chain. The total SO₂ emissions and CO₂ emissions of these sectors accounted for 81% and 76% of the total national SO₂ emissions and CO₂ emissions, respectively.