Achieving carbon neutrality is crucial for the global economy to ensure sustainable development. Quantitative approaches are needed to track the emissions and determinants thereof. The Generalized Divisia Index (GDI) has received wide attention to quantify major factors driving CO 2 emissions. However, there has been no research on the application of GDI to decompose the relative variables, such as Aggregate Carbon Intensity (ACI). What is more, GDI has not been applied for spatial decomposition. To address these gaps, the present study constructs temporal-spatial GDI models to decompose the dynamics in ACI of thermal electricity generation. The case of China during 2000-2019 is considered. The results suggest that East, Central, and Northwest regions contributed to the mitigation of national ACI, whereas North and Northeast lagged behind. The temporal decomposition results imply that CO 2 emissions is the major factor causing ACI increase, whereas energy-mix promotes reduction in ACI. Energy consumption can be decoupled from ACI, but it is cumbersome to decouple CO 2 emission and electricity production from ACI. The spatial decomposition results indicate that CO 2 emission and energy consumption induce spatial differences to the highest extent.