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.

Impacts of slope climbing of urban expansion on global sustainable development

The rapid pace of global urbanization is profoundly reshaping our planet and will have significant implicatins for global sustainable development.According to the United Nations,urbanization is projected to surge from 56%in 2020to 67%by 2050,an 11%increase.'The expanding urban population has led to the con-version of an increasing amount of natural land into urban areas.It is anticipated that by 2030,urban areas across the globe will cover approximately 587 million km2,which is double the rate of population growth.2 In general,the availability of flat land resources suitable for both production and habitation is limited,and the relentless pace of urbanization consistently encroaches upon these resources.Consequently,adopting the"slope climbing"model for urban expansion has been prevalent in numerous regions and nations as a strategy to address the conflict between urban expansion and the scarcity of flat land resources.

Carbon dioxide(CO_(2))emissions from the service industry,traffic,and secondary industry as revealed by the remotely sensed nighttime light data

Exploring carbon dioxide(CO2)emissions from human activities is essential for urban energy conservation and resource management.Remotely sensed nighttime lights from the Suomi NPP-VIIRS provide spatial consistency in and a low-cost way of revealing CO2 emissions.Although many researches have documented the feasibility of the Suomi NPP-VIIRS data for assessing CO2 emissions,few have systematically revealed the ability of nighttime lights for evaluating CO2 emissions from different industries,such as service industry CO2 emissions(SC),traffic CO2 emissions(TC),and secondary industry CO2 emissions(IC).Here,China was selected as the experimental subject,and we comprehensively explored the relationships between the nighttime lights and SC,TC,and IC,and investigated the factors mediating these relationships.We found that without considering other factors,the nighttime lights only revealed up to 51.2%of TC,followed by 41.7%of IC and 22.7%of SC.When controlling for city characteristic variables,the models showed that there were positive correlations between the Suomi NPP-VIIRS data and SC,IC,and TC,and that nighttime lights have an Inverted-U relationship with SC.The Suomi NPP-VIIRS data are more suitable for revealing SC,TC,and IC in medium-sized and large-sized cities than in small-sized cities and megacities.