【作者】 徐丽；

【导师】 曲建升；

【作者基本信息】 兰州大学 ， 地理学·自然地理学， 2023， 博士

【摘要】 碳排放引发的全球气候变化问题已经引起了国际社会的广泛关注。作为碳排放大国,中国政府的节能减排行动可以显著减缓气候变化,有助于实现联合国倡导的可持续发展目标。2020年,中国正式提出争取在2030年实现碳达峰、在2060年实现碳中和的目标,在主动承担和作为的前提下,中国减排的压力持续增加。城市作为人类活动的主要聚集地,贡献了中国约80%的二氧化碳。城市发展的必要性和实现减排承诺的迫切性之间的矛盾使得城市成为绿色低碳发展战略的主阵地。实现城市高质量发展的同时控制碳排放的增长速度就成为城市发展和碳减排过程中必须解决的问题。因此,探究城市发展对碳排放的影响是实现城市低碳发展的前提,这有助于把握中国城市发展阶段及其对碳排放的影响规律,可为中国有效应对气候变化问题,构建城市可持续发展路径提供数据基础与科学依据。基于以上背景,本研究以中国287个地级及以上城市作为研究对象,按照城市发展评价、城市碳排放分析、城市发展对碳排放的影响三条主线展开研究,其中,城市发展评价和城市碳排放分析是基于夜间灯光数据集和城市建成区数据集展开的。在城市发展方面,综合人口、经济、城市建设和社会四个子系统构建城市发展综合评价指标体系,计算了城市发展综合得分和发展类型,并对其发展类型的时空变化特征、子系统组合和持续时长进行分析。在城市碳排放方面,在确定碳排放总量和分部门碳排放数据精度的基础上,分析了城市碳排放的时空变化和分布特征。在城市发展对碳排放的影响方面,针对工业、交通、建筑能耗和电力四个方面碳排放,采用(有调节的)多重中介模型分析了城市发展的碳排放影响,并得出城市发展对碳排放的传导路径和路径的传导效应。最后,考虑到城市类型可能会使城市发展的碳排放影响产生偏差,在城市发展的碳排放影响和传导效应已经明确的基础上,进一步分析了扩张城市和收缩城市的发展对碳排放的影响及其差异。主要结论如下:(1)基于夜间灯光数据改进的城市建成区提取流程能够有效降低夜间灯光过饱和现象和城市外围植被区灯光溢出问题,可以批量化快捷实现城市建成区范围提取。通过与已发布的中国多时期土地利用遥感检测数据集和中国城市建成区数据集进行建成区面积的时间检验和空间检验,以及建成区形状精度检验,结果显示最低相关性为0.85,平均总体精度为83.25%,平均Kappa系数为0.7413,本文提取的城市建成区平均紧凑度为0.24,平均形状指数为5.66,接近两类验证数据的平均值,提取结果在建成区面积和形状方面具有较高的准确度。(2)地级及以上城市发展呈现正常波动为主,扩张与收缩并存,发展状态以短期为主的特征。通过构建城市综合发展评价体系对地级及以上城市的综合发展、人口、经济、城市建设和社会子系统发展的类型、时空变化、组合情况和长短期进行分析,结果显示,城市综合发展以正常波动为主,扩张与收缩并存;变化率高/低值空间聚集在发展水平较低的资源枯竭型城市、老工业城市和偏远的山区型城市。人口和经济子系统以正常波动和收缩为主,分别空间聚集在人口高基数区,经济欠发达地区以及人口流出地区和资源富集和重工业为主的区域。社会和后期的城市建设子系统以扩张为主,空间聚集在发展早、水平高的地区。从子系统发展的组合关系和城市发展状态的长短期而言,全子系统组合较少;经济-城市建设-社会多处于扩张状态。城市综合和子系统发展处于长期发展状态的较少。不连续时段变化和阶段性发展是城市发展的主要趋势。(3)碳排放总量和部门碳排放量均呈现增加趋势。通过对全球大气研究排放数据库进行时空分析,结果显示,建成区碳排放总量和部门碳排放量在时间趋势上均呈现增加趋势。在空间分布上,碳排放总量呈现出北方高于南方、沿海高于内陆、省会城市高于周围城市的空间格局。工业碳排放聚集在工业基地和资源省份;电/热力碳排放聚集在人口数量多、经济发展需求大、供暖需求大和城市发展水平高的地区;交通碳排放聚集在城市基础建设好,人口聚集和经济水平高的地区;建筑能耗碳排放聚集在人口数量多,家庭电气化程度高的地区。(4)城市发展的碳排放影响和传导效应。通过中介模型和有调节的中介模型对城市发展的碳排放影响进行分析,结果显示,城市发展无法直接影响工业、建筑能耗、交通、电力碳排放和碳排放总量,需要通过工业生产总值、工业部门固定资产投资、工业碳排放强度、房地产中住宅投资总额、三产占比、社会消费品零售总额、道路密度、道路长度、私家车拥有量、建成区面积和全社会用电量共11条路径分别影响部门碳排放,进而影响碳排放总量,并且在每条路径中均存在调节效应。在不考虑工业碳排放强度的情况下,城市发展的碳排放总效应为-0.0037,抑制效应为-0.0474,促进效应为0.0437。全社会用电量、道路密度、私家车和工业生产总值是抑制碳排放的主要中介因素。三产占比、道路长度、建成区面积和社会消费品零售总额是促进碳排放的主要中介因素。(5)扩张/收缩城市的碳排放影响差异。在工业碳排放方面,城市扩张发展会通过对工业生产总值、二产占比和能源消耗造成负向影响,降低工业碳排放和碳排放总量,城市收缩发展的碳排放影响与之相反且拉动作用更加明显。工业固定资产投入增加会显著拉动收缩城市的工业碳排放,但不一定会造成扩展城市的碳排放增加。社会消费品零售总额和三产占比均会促进扩张城市和收缩城市的建筑能耗碳排放增加,但在处于严重收缩的城市中,可能会由于第三产业发展缓慢而造成建筑能耗碳排放的降低。城市扩张发展会通过提高道路密度,降低对私家车的依赖性在一定程度上抑制交通碳排放,收缩城市与之相反。社会用电量和工业用电量会随城市扩张而轻微下降,但在收缩城市中则增长明显。综合以上结论可以看出,城市高质量发展可以在一定程度上抑制城市碳排放的增加。城市发展过程中可以通过合理控制产业结构,布局产业类型和配置投入-产出比例,倡导合理消费方式,规划道路以实现高通达性和路网连通度等措施控制城市碳排放量,但也存在由于产业结构偏重,城市盲目扩张和低路网密度带来的私家车依赖性高,高消费水平等拉动城市碳排放的增长。虽然我国仅用了30年的时间完成了发达国家几十年的城市化进程,且城市建设范围和基础设施建设已经基本完备并具有长效性,正是因为这一特点,城市在发展方向、发展路径、转型或升级的过程中需要有更远见的意识。相关部门应该根据城市发展阶段和定位、支柱产业类型和特征、人口承载力和活力以及城市吸引力等差别化的定制减排政策,以实现城市绿色低碳转型和可持续发展。更多还原

【Abstract】 Global climate change caused by carbon emissions has attracted wide attention in the international community.As a large developing country,the energy savings and emission mitigation actions from the Chinese government could significantly mitigate climate change and achieve the United Nations promotion of sustainable development goals.In 2015 and 2020,China presented proposed peak carbon dioxide emissions and carbon neutrality targets,respectively,making us great pressure on carbon emission reduction.The city is one of the main gathering places of human activities.As the main gathering place of human activities,the city is an important source of energy consumption and carbon emissions.According to statistics,approximately 80%of China’s carbon emissions were attributed to urban areas,which make the city the focus of carbon emission reduction actions and low-carbon development strategy.A comprehensive understanding of the relationship between urban development and carbon emissions in China can provide a reference for China’s effective response to climate change and the construction of sustainable urban development paths.This paper takes 287 cities above the prefecture level in China as the research object.Through the correction of multi-source night light data and the construction of the night-light data set,the city built-up areas of 287 cities at the prefecture level and above in China during 2000-2020 were identified.Based on city built-up areas and the ERGDR database,we calculate the total carbon emissions and the carbon emissions of the industrial sector,transportation sector,building sector,and the electric and thermal sector in urban built-up areas,and make an overall evaluation of its temporal and spatial differentiation.Next construct a comprehensive evaluation index system for 287 cities above the prefecture level in China in 2000-2020 from the population,economy,urban construction,and environment using subjective and objective weighting methods,calculate urban development score,and assess the urban development state in four time periods.Then,the impact of urban development on carbon emissions was measured from the aspects of industrial carbon emissions,transportation carbon emissions,residential carbon emissions,and electric heating carbon emissions through a multiple mediation model.The conduction effects of each variable and conduction pathways were analyzed and compared upon this foundation.Finally,considering city type may bias conclusions from the effect of city development on carbon emissions,we further analyzed the impacts and differences of expansion/contraction city development on carbon emissions based on conclusions that the overall impact of city development on carbon emissions.The main conclusions are as follows:(1)Improved workflow of urban built-up area extraction based on night-time light data enables efficient reduce the problem of light supersaturation and light spill-over in vegetation zones at peri-urban,which can also be achieved in urban built-up areas extraction in batch and easily.To test the accuracy of urban built-up areas and urban built-up shape,we compare our results with China’s national land use and cover change and the Dataset of urban built-up areas in China.The spatial and temporal contrasts of the urban built-up area showed that the lowest correlation is0.85,the average Overall Accuracy is 83.25% and the average Kappa coefficient is0.7413.The contrasts of urban built-up shape showed that the average compactness is0.24 and the average shape index is 5.66,which closely matches the average value of two published validation datasets.(2)Urban development at the prefecture level or above presents the features that most cities fluctuate within the normal range,urban expansion development and urban contraction development coexist and the urban developmental state is mainly short-term.The analysis of development types,spatial-temporal variations,subsystem combinations,and long-short term situations of urban and urban subsystems(population,economic,urban construction,and society)was performed by constructing comprehensive urban development evaluation systems.Results of the overall urban development showed that most cities fluctuate within the normal range,some cities are on the expansion and some cities are on the contraction.Their spatial aggregations of high/low change rates are focused on resource-exhaustion cities,old industrial cities,and cities in remote and mountainous zones.Results of the population and economic subsystem showed that most sample cities are dominated by normal fluctuations and contraction.The spatial aggregations of population subsystem are focused on the regions with high population base,economically underdeveloped,or population outflow.The spatial aggregations of the economic subsystem are focused on the regions with enriched resources and heavy industry.Results of the social and late urban construction subsystem showed that most sample cities are dominated by normal fluctuations and expansion.Their spatial aggregations are focused on the region with development early and high-level.Furthermore,the combination of full subsystems was less,and the combination of economic-urban construction-society majority in expansion.Few fully urban subsystems were in the long-term development state.A low number of full cities and subsystems were in the long-term development state.The change of discontinuous periods and phrased development is the major trend of urban development.(3)The total carbon emissions and sector carbon emissions presented increasing trends.Spatial and temporal analysis of carbon emissions from the Emissions Database for Global Atmospheric Research(EDGAR)revealed that the total carbon emissions and sector carbon emissions presented increasing trends.Spatially,the spatial distribution of carbon emission shows a pattern that the north is higher than the south,coastal cities higher than inland cities,and provincial capital cities higher than surrounding cities.The carbon emission from the industrial sector clustered mainly in the industrial bases and resource-based provinces.The carbon emission from the electric sector clustered mainly in the regions with high populations,economic demand,heating demands,and development levels.The carbon emission from the traffic sector clustered mainly in the regions with better infrastructure buildings,intensive population,and high-level economic.The carbon emission in the building sector clustered mainly in high populations and high household electrification.(4)We analyzed the impact and conduction path of city development on carbon emission using the mediation model and mediation model with moderating effects.The urban development was unable to directly affect sector carbon emissions(industry,building,traffic,and electricity)and total carbon emissions.However,urban development can impact sector carbon emissions via eleven paths,which in turn affects total carbon emissions.These paths include gross industrial output,fixed asset investment in the industry,the industrial carbon emission intensity,total residential investments,proportion of the tertiary industry,total retail sales of consumer goods,the density of road network,road length,private vehicles possession,build-up area,and the whole-of-society electricity consumption.Moreover,each path was found moderating effects.The total effect of urban development on carbon emission is-0.0037 without considering the industrial carbon emission intensity.The inhibitory effect is-0.0474,and the facilitation effect is 0.0437.The whole-of-society electricity consumption,the density of the road network,private vehicle possession,and gross industrial output was the dominant mediation factors inhibiting carbon emissions.The proportion of the tertiary industry,road length,build-up area,and total retail sales of consumer goods were the dominant mediation factors promoting carbon emissions.(5)We analyzed the impact of city development on carbon emission rate variation from the perspective of expansion/contraction city.In terms of industrial carbon emissions,urban expansion reduces industrial carbon emissions and total carbon emissions by negatively affecting industrial GDP,the secondary sector of economy and energy consumption,while urban contraction has the opposite and more pronounced pulling effect on carbon emissions.The increased industrial fixed asset investment will significantly contribute to industrial carbon emissions in the contracting city,but not necessarily to the increase in carbon emissions in the expanding city.Both total retail sales of consumer goods and the share of tertiary industry contribute to the increase of carbon emissions from building energy consumption in expanding and contracting cities,but in cities in severe contraction,there may be a decrease of carbon emissions from building energy consumption due to the slow development of tertiary industry.Expanding cities will to some extent suppress traffic carbon emissions by increasing road density and reducing the dependence of private cars,while shrinking cities is the opposite.Social and industrial electricity consumption will slightly decrease with urban expansion,but increase significantly in shrinking cities.Based on the above conclusions,it can be seen that high-quality urban development can restrain the increase of urban carbon emissions to a certain extent.In the process of urban development,urban carbon emissions can be controlled by rational industrial structure,the industrial layout and input–output relationship,advocating low-carbon consumption,the road planning to attain high accessibility and road network connectivity.However,urban carbon emissions are likely to continue to grow,driven by industrial structure imbalance,the blind expansion of urban space and low road densities,high-consumption and high private vehicles reliance.China has only used 30 years to complete the process of urbanization in the developed countries for several decades,and infrastructure-making have been basically complete.Due to the long-term effectiveness of urban infrastructure-making,the state and local government should have a forward-looking awareness when planning urban development direction,development path,transformation or upgrading.Relevant departments should describe carbon reduction policies according to the different urban stages,pillar industries,the carrying capacity and vitality of the population,and the attractiveness of the city.更多还原