Spatial-Temporal Variation Of Carbon Dioxide Emissions And Its Rela-Tions To Nighttime Surface Temperature In Yangtze River Delta Region Based On Night Light Imageries

As the largest developing country in the 21st century,China is undergoing a gradual transformation from a planned economy to a market economy,and has achieved amazing economic growth.While economic development has brought prosperity and progress to China,it has also increased the amount of greenhouse gas-es in the atmosphere.China became the world's largest carbon dioxide?CO₂?emitting country in 2008.In the face of huge pressures to reduce emissions,reducing CO₂emissions has become a common concern in the academic community.The Yangtze River Delta region has the highest level of urbanization and eco-nomic growth in China,and is one of the six typical megacities in the world.Such rapid economic growth and urbanization will inevitably lead to a high concentration of energy consumption,which will greatly increase CO₂ emissions.The increase of carbon emissions will bring many impacts on urban environmental health.One of the more significant impacts is the change of surface temperature.How to scientifically and accurately analyze the spatiotemporal evolution characteristics of carbon emis-sions in the Yangtze River Delta region and reveal its inherent relationship with sur-face temperature has important practical significance for the implementation of re-gional emission reduction strategies.However,current statistics on energy consump-tion are based on national or provincial levels,and there is a lack of spatial informa-tion on carbon emissions on a smaller scale.The night light data can reflect the inten-sity of human activity.Studies at home and abroad have proven that it is feasible to use night light data for carbon emissions estimation,but the research is mainly fo-cused on before 2013,mostly at the municipal,provincial or national level Analysis,and relatively little research on the internal relationship between carbon emissions and surface temperature.In order to realize the spatial informationization of carbon emissions,the study selected night light imageries and energy consumption statistics data as data sources,and constructed a carbon emission simulation model in the Yangtze River Delta re-gion from the pixel scale.Secondly,in order to reveal the internal mechanism of car-bon emissions and surface temperature,considering that the surface temperature dur-ing the day is susceptible to the influence of the sun,the study chose the night surface temperature as the data source.Then,using trend analysis and spatial autocorrelation analysis,the time-varying characteristics,spatial distribution characteristics,spatial trend characteristics,and spatial autocorrelation distribution patterns of carbon emis-sions in the Yangtze River Delta region from 2000 to 2017 were analyzed.Finally,the spatial and temporal characteristics of carbon emissions and night-time surface tem-perature are compared and analyzed.The study show that:?1?Carbon emissions in the Yangtze River Delta region increased from 440.88million tons in 2000 to 1315.02 million tons in 2017,but the growth rate has gradu-ally slowed down.The average annual growth rates of 2000-2005,2005-2010,and2010-2017 were 9.42.%,6.79%,and 4.59%.In terms of spatial distribution,the high-value carbon emission areas are mainly distributed in Shanghai,Suzhou and its neighboring cities,which are obviously flaky.The low-value areas are mainly distri-buted in Lishui and Luzhou in Zhejiang,as well as in Lu'an,Anqing and Chizhou in Anhui Province.In terms of spatial trends,the area of carbon emissions in the Yangtze River Delta region,which has remained basically unchanged for the past 18years,accounts for 70.14%,mainly in the western and southern areas of Anhui and Zhejiang.The extremely significant growth area occupies the smallest area,account-ing for only 0.58%,mainly distributed in the periphery of Shanghai's urban center.From the perspective of spatial autocorrelation,the degree of spatial agglomeration of carbon emissions in the Yangtze River Delta region from 2000 to 2010 continued to increase,and the degree of spatial agglomeration of carbon emissions from 2011 to2017 remained basically unchanged.The significant LL concentration area occupies the largest area,mainly distributed in the western and southern parts of Anhui and Zhejiang.The significant HH concentration area is mainly distributed in Shanghai,southern Jiangsu and northern Zhejiang,and its area increased from 7.86%in 2000 to14.69%in 2017,while the HL and LH concentration areas occupy less area.?2?A comparative analysis of the time variation characteristics of carbon emissions and night-time surface temperature shows that the carbon emissions and night-time surface temperature of the Yangtze River Delta region show an upward trend from 2000 to 2017.The correlation coefficient between the two is 0.413?P<0.1?,which is a positive correlation.The cities with the fastest increase in carbon emissions and nighttime surface temperature are Jiangsu Province,followed by Zhe-jiang Province.Comparative analysis of spatial distribution characteristics shows that carbon emissions and nighttime surface temperature have a high consistency in the spatial distribution pattern,with Shanghai,Suzhou,Wuxi,Nanjing,and Zhenjiang being the most obvious.Carbon emissions from low emission areas to high emission areas,the corresponding nighttime surface temperature rose from 25.84?to 28.80?.The comparative analysis of trend characteristics shows that the Slope mean of the corresponding nighttime surface temperature increases from the basic unchanged carbon emission to a significant increase,while the Slope mean of the nighttime sur-face temperature decreases to 0.052 when the carbon emission increases extremely significantly.A comparative analysis of spatial autocorrelation characteristics shows that both carbon emissions and night-time surface temperature in the Yangtze River Delta region show significant positive spatial accumulation characteristics,and the HH and LL accumulation areas both exhibit obvious flaky distributions,but there is a certain difference in the proportion of area occupied.Among them,the local spatial correlation index of Shanghai and Zhejiang's carbon emissions and night-time surface temperature are highly consistent in spatial distribution.On the scale of the year,from2000 to 2017,the carbon emissions in the Yangtze River Delta region had a signifi-cant positive correlation with the maximum,minimum,and average of surface tem-perature at night,and all passed a significance test of 0.01.From an interannual scale,carbon emissions have an important impact on the rise in nighttime surface tempera-ture.The area with positive correlation between carbon emission and night surface temperature accounted for 89%,among which the relatively significant positive cor-relation and the extremely significant positive correlation accounted for 12.08%.