Differentiated effects of morphological and functional polycentricurban spatial structure on carbon emissions in China: an empiricalanalysis from remotely sensed nighttime light approach

Understanding the relationship between urban development and environmental sustainability to achieve‘double carbon’goals in China can be strengthened by evaluating the environmental effect of urban spatial structure(US).However,there have been few studies that consider the differentiated effects of polycentric US(PUS)on carbon emissions from both functional and morphological perspectives simultaneously.Thus,taking China’s 31 provinces as experimental subjects,our study developed a novel framework with remotely sensed nighttime light(NTL)data to quantify morphological PUS(MPUS)and functional PUS(FPUS)from 2000 to 2019.Then,from these two dimensions,differentiated effects of PUS on carbon emissions were further examined.Results indicated that NTL data presented high potential in quantifying MPUS and FPUS.The effect of FPUS on carbon emission-cutting outperformed that of MPUS.In addition,the spillover effect effectively enhanced the decreasing effect of the FPUS on carbon emissions.Our empiricalfindings can provide guidance for the government in developing strategies for reducing carbon emissions and optimizing USs.