Study On The Spatial-temporal Pattern Of Carbon Emission And Its Response To Urbanization In Zhejiang Province

Global warming caused by increasing carbon dioxide（CO₂）concentration is one of the international issues.As the largest carbon emitter,China is facing severe pressure to reduce CO₂ emissions.It is urgent for China to coordinate the relationship between economic growth and emission reduction goal,so as to promote the low-carbon development.Rapid urbanization is an important driving factor for the continuous growth of China’s carbon emissions,and it is also an important perspective for carbon emission reduction at the stage of social development transformation in China.In the context of the continued demand for national economic growth and the long-term industrial transformation,it is helpful to explore the impact of urbanization on carbon emissions,which can help share the carbon reduction pressures of China.And it can also help to guide urban construction from a low-carbon development perspective,promoting the continuous coordination between urban development and environmental effects.Limited by the availability of data,the complete estimation of carbon emission based on IPCC method can only be achieved at the provincial level.In this case,using panel data of 30 provinces（excluding Tibet,Hong Kong,Macao and Taiwan）from year1995 to 2015,this study first built a carbon emission model based on nighttime light remote sensing image and urban carbon emission data,which decomposed provincial carbon emissions to more detailed scales.On this basis,taking Zhejiang Province as the research area,we analyzed the spatial-temporal pattern of urban carbon emissions from year 1995 to 2015.In order to measure the impact of urbanization on carbon emissions,the spatial-temporal coupling relationship between the overall urban expansion and carbon emissions was studied from a dynamic perspective.And then based on the multi-dimensional structure of urbanization（land,economy,population,society）,considering the spatial autocorrelation of carbon emissions,the spatial lag model（SLM）was applied to explore the specific response of carbon emissions to the multidimensional structure of urbanization,so as to provide a reference for urban development under the low-carbon demand.The main contents and conclusions of this study are as follows:（1）Urban carbon emission inversion model construction based on nighttime light remote sensing data:Based on the nighttime light remote sensing data,this study first used the object-based threshold method to extract the urban area of China from year1995 to 2015.The overall accuracy of extraction is more than 90%,and the average Kappa coefficient is 0.66,indicating that the accuracy of urban extraction is good and can be used as a data basis for subsequent research.With reference to the IPCC method,based on the energy consumption data and purchased electricity data of 30 provinces in China,the urban carbon emissions of 30 provinces in China from year 1995 to 2015were calculated,including industry,construction,transportation,business and urban resident lives.Combining the statistical carbon emission data and nighttime light data of urbans from 30 provinces from year 1995 to 2015,a panel model was built to conduct the study of carbon emission inversion.As a result,the carbon emission data was inverted to the spatial scale of 1km×1km.On this basis,the urban carbon emissions of municipal and county-level administrative units were obtained in Zhejiang Province.Accuracy evaluation was conducted by the statistical carbon emission data of 11prefecture-level cities and 90 counties from Zhejiang Province in year 2015.The R² at the municipal and county scales were 0.7715 and 0.7124,respectively,and the RMSE were 6.355 million tons and 748,300 tons,respectively,indicating good inversion accuracy.It revealed that the estimation of carbon emissions based on nighttime light remote sensing data can provide a good data basis for subsequent research.（2）Multi-scale analysis of the spatial-temporal dynamic pattern of urban carbon emissions（1995-2015）:Taking Zhejiang Province as the research area,the Exploratory Spatial Data Analysis（ESDA）method was used to study the spatial-temporal dynamic pattern of urban carbon emissions from 1995 to 2015 at the municipal and county scales,respectively.The results shows:（1）From year 1995 to 2015,the urban carbon emissions in Zhejiang Province first showed growth with rapid speed,and then followed by slower speed.（2）The overall spatial patterns of urban carbon emissions in Zhejiang Province were different at the municipal and county levels,of which the spatial differences of carbon emissions at the municipal level showed a gradual reduction trend,while that of the county level remained unchanged.There was no significant spatial autocorrelation of municipal urban carbon emissions,while county-level urban carbon emissions had significant spatial autocorrelation.In terms of time series,Global Moran’s I of urban carbon emission showed decreasing trend both at the municipal level and the county level,indicating that the spatial agglomeration of urban carbon emissions in Zhejiang Province had weakened.（3）The local spatial autocorrelation types of county-level carbon emissions were mainly positive,of which the high-high agglomeration types were mainly located at the northeastern region of Zhejiang Province,and the low-low agglomeration types were mainly located at the southwestern region of Zhejiang Province.From year 1995 to 2015,the scope of all the agglomerations was slightly reduced,further indicating that the spatial agglomeration patterns of carbon emissions were gradually weakening.（4）Comparison of the spatial-temporal patterns of urban carbon emissions showed differences in the spatial pattern at different scales.Smaller research scales can better reveal the spatial pattern characteristics.Therefore,when conducting carbon emission related research,its scale effect should be fully considered.（3）Research on the spatial-temporal coupling relationship between urban expansion and carbon emissions:In order to measure the relationship between the overall urban expansion and carbon emissions,this study first analyzed the spatial-temporal patterns of carbon emissions and urban expansions in Zhejiang Province.Then,the gravity center model was used to analyze the spatial relationship between the carbon emission and the urban land.The coupling coordination degree model was used to measure the coordinated development degree of urban expansion and carbon emission over a long time series.And on this basis,the coordinated development trend was predicted by 2020.The results showed:（1）In terms of the growth rate,the temporal trend and spatial distribution patterns were consistent of carbon emissions and urban expansion.The growth rate first raised,and then decreased.In space,the locations with large urban areas had higher carbon emissions.（2）The distance between the gravity center of carbon emissions and that of urban land showed a decreasing trend,indicating that the spatial coupling between them was gradually increasing.（3）The level of coupling coordination between carbon emissions and urban expansion presented an inverted“U”curve,which was consistent with the Environmental Kuznets Curve（EKC）.（4）The prediction results showed that from year 2015 to 2020,with the effective regulation of urban land expansion and carbon emissions,all the municipal administration will transform to land intensive and low-carbon development pattern.（4）Research on the impact of multi-dimensional urbanization on carbon emissions and emission reduction strategies:In view of the spatial autocorrelation of carbon emissions,this study chose spatial lag model（SLM）to measure the impact of multidimensional urbanization structure（land,economy,population and society）on carbon emissions.The results showed:（1）Each dimension of urbanization had different effects on carbon emissions in Zhejiang Province:Land urbanization exacerbated carbon emissions through the expansion and fragmentation of urban land,while enhancing the connectivity between urban land can suppress carbon emissions.As for economic urbanization,the increase of secondary industry proportion significantly increased carbon emissions,but the impact of economic growth weakened with the transformation of economic development pattern.Population urbanization played a role as suppressing carbon emissions by increasing the urban population ratio and population density.On the one hand,social urbanization promoted carbon emissions through consumption behavior,and on the other hand,it slowed down carbon emissions through the improvement of residents’awareness.（2）Under the demand for low-carbon development,the future urban land planning in Zhejiang Province should enhance the functions of the existing urban region and formulate compact urban land use forms,so as to improve urban land use efficiency.In addition,Zhejiang Province should continue the task of economic reform,optimize the industrial structure,and continue to emphasize the quality of economic growth rather than quantity and scale.As population urbanization continues,in the process of urbanization,raising public awareness of low-carbon life and green consumption is also an inevitable requirement for low-carbon development.