Spatial decomposition of city-level CO₂ emission changes in Beijing-Tianjin-Hebei

China is the world's largest carbon emitter, and the Beijing-Tianjin-Hebei metropolitan region is an energy-intensive area in China. Under the requirements of the national policy of regional green development, the Beijing-Tianjin-Hebei region needs to shift to a low-carbon development mode to achieve regional emission reduction targets. The varying characteristics of industrial carbon emissions resulting from differences in the industrial development and resource endowment of each city make it difficult to implement the same emission reduction policy, so different cities need to be treated differently. Based on data from three provinces and eight cities in the region from 2002 to 2016, this study used the multi-regional (M-R) spatial decomposition method to compare the carbon emissions and the effects of their influencing factors in each city, so as to provide a targeted emission reduction policy for each city. The estimation results revealed that carbon emissions in the Beijing-Tianjin-Hebei region peaked in 2012, and energy intensity and population size are the main reasons for the differences in carbon emissions at the provincial level. At the city level, Tangshan, Handan and Shijiazhuang are high carbon emission cities, while Hengshui, Baoding, Langfang, Qinhuangdao and Xingtai are low carbon emission cities. The total amount of carbon emission in all industries in Tangshan ranks the first, and economic scale and energy intensity are the main reasons for the high carbon emissions in its manufacturing and transportation sectors. Energy intensity and energy structure are the main reason why the carbon emission of Handan is higher than that of Baoding, a city with the same economic level. Shijiazhuang has high energy efficiency, but its economic development and carbon emissions have not yet been decoupled. Hengshui's high energy intensity is an obstacle to emission reductions in all industries. Xingtai's energy structure contributes to carbon emission reduction. The current industrial structures of Qinhuangdao, Langfang, and Shijiazhuang may help these cities reduce emissions. Lastly, we offer recommendations for urban emission reduction policies.