Spatio-temporal variation and decoupling effects of energy carbon footprint based on nighttime light data: Evidence from counties in northeast China

In the context of global climate change, it is essential for each county, as a fundamental geographical unit for achieving carbon reduction and energy conservation, to assess its carbon footprint to promote sustainable development. To analyze the energy-related carbon emissions of 221 counties in Northeast China, this study establishes a fitting model using nighttime light data and carbon emissions information. The coefficient R² value of 0.945, with Root Mean Square Error (RMSE) and Relative Error (RE) values of 8501.37 Mt and 2.32%, respectively. Additionally, exploratory spatio-temporal data analyses and standard deviation ellipse methods were used to explore the spatial patterns and spatio-temporal evolution of carbon footprints. The results show that the average annual growth rates of carbon footprint and carbon deficit are determined to be 6.17 % and 7.28%, respectively. Prior to 2013, both the carbon footprint and carbon deficit experienced rapid growth; however, a brief decline occurred thereafter. Starting in 2016, both metrics began to expand again. It is observed that the carbon footprint is expanding westward, while the carbon deficit shows a comparable pattern, radiating from the center to the surrounding areas. The carbon footprint demonstrates significant spatial autocorrelation, with local aggregation predominantly influenced by high-high (HH) and low-low (LL) aggregation. The center of gravity and coverage of the carbon footprint has shifted southwest, displaying a relatively stable development trend. Moreover, the Tapio decoupling model is employed to analyze the relationship between economic development and carbon emissions. The results show that carbon emissions and economic development are consistent with a three-stage decoupling pattern. Overall, the decoupling state is characterized by a growth linkage; however, the decoupling stability is relatively weak, with fluctuations between decoupled and coupled states occurring repeatedly.