A multi-sectoral decomposition analysis of city-level greenhouse gas emissions: Case study of Tianjin, China

To better understand how city-level greenhouse gas (GHG) emissions have evolved, we performed a multi-sectoral decomposition analysis to disentangle the GHG emissions in Tianjin from 2001 to 2009. Five sectors were considered, including the agricultural, industrial, transportation, commercial and other sectors. An industrial sub-sector decomposition analysis was further performed in the six high-emission industrial branches. The results show that, for all five sectors in Tianjin, economic growth was the most important factor driving the increase in emissions, while energy efficiency improvements were primarily responsible for the decrease in emissions. In comparison, the influences from energy mix shift and emission coefficient changes were relatively marginal. The disaggregated decomposition in the industry further revealed that energy efficiency improvement has been widely achieved in the industrial branches, which was especially true for the Smelting and Pressing of Ferrous Metals and Chemical Raw Materials and Chemical Products sub-sectors. However, the energy efficiency declined in a few branches, e.g., Petroleum Processing and Coking Products. Moreover, the increased emissions related to industrial structure shift were primarily due to the expansion of Smelting and Pressing of Ferrous Metals; its share in the total industry output increased from 5.62% to 16.1% during the examined period.