Evaluating coupling coordination between urban smart performance and low-carbon level in China’s pilot cities with mixed methods

Evaluating coupling coordination between urban smart performance and low-carbon level in China’s pilot cities with mixed methods | Scientific Reports

Abstract

The construction models of smart cities and low-carbon cities are crucial for advancing global urbanization, enhancing urban governance, and addressing major urban challenges. Despite significant advancements in smart and low-carbon city research, a consensus on their coupling coordination remains elusive. This study employs mixed-method research, combining qualitative and quantitative analyses, to investigate the coupling coordination between urban smart performance (SCP) and low-carbon level (LCL) across 52 typical smart and low-carbon pilot cities in China. Independent evaluation models for SCP and LCL qualitatively assess the current state of smart and low-carbon city construction. Additionally, an Entropy–TOPSIS–Pearson correlation–Coupling coordination degree (ETPC) analysis model quantitatively examines their relationship. The results reveal that smart city initiatives in China significantly outperform low-carbon city development, with notable disparities in SCP and LCL between eastern, non-resource-based, and central cities versus western, resource-dependent, and peripheral cities. A strong positive correlation exists between urban SCP and overall LCL, with significant correlations in management, society, and economy, and moderate to weak correlations in environmental quality and culture. As SCP levels improve, the coupling coordination degree between the urban SCP and LCL systems also increases, driven primarily by economic, management, and societal factors. Conversely, the subsystems of low-carbon culture and environmental quality show poorer integration. Based on these findings, this study proposes an evaluation system for smart and low-carbon coupling coordination development, outlining pathways for future development from the perspective of urban complex systems.

Introduction

Cities, as centers of population and economy, play crucial roles in cultural exchange, social integration, transportation, communication, and disaster response in modern societal development 1, 2. According to the United Nations Human Settlements program’s “2022 World Cities Report”, as of 2021, the global urbanization rate has reached 56%, and it is projected that by 2050, an additional 2.2 billion people will live in cities, increasing the urbanization rate to 68% 3. North America and European countries are approaching urbanization saturation, with little fluctuation expected, while urbanization in Asia and Africa will accelerate notably 4. Particularly in China, the world’s second-largest economy, as of 2022, the urbanization rate is only 64.7%, ranking 96th globally, indicating significant potential for growth compared to developed countries like the USA and the UK 5. The Chinese government places high importance on urbanization development. It was clearly stated in the “2020 State Council Government Work Report” that new urbanization is a key measure for achieving China’s modernization. Moreover, in the “14th Five-Year Plan (2021–2025) and the Long-Range Objectives Through the Year 2035”, detailed strategies are outlined for optimizing the urban layout and promoting urban–rural integration, among other policies to advance urbanization 6. However, urbanization, as a process of continuous concentration of population and industrial elements in cities, while bringing opportunities for economic growth and social development, also presents a series of challenges such as environmental pressure, resource constraints, and increased demand for services 7, 8.

In 2008, the American company IBM introduced the concept of a “Smart Planet”, which garnered widespread attention globally 9. The concept of a smart city, as a specific application within this framework, aims to enhance urban management and service efficiency through the integration and innovative application of Information and Communication Technology (ICT), thereby improving the quality of life for residents, optimizing resource use, reducing environmental impact, and promoting economic development and social progress 10, 11. Currently, the smart city construction model is seen as one of the effective means to advance global urbanization, improve urban governance, and solve major urban issues 12. In 2009, IBM released the “Smart Planet: Winning in China” plan, outlining China’s five major thematic tasks in constructing a “Smart Planet” (sustainable economic development, corporate competitiveness, energy efficiency, environmental protection, and social harmony) 13. The construction of smart cities, as a key measure to achieve these thematic tasks, has received significant attention from the Chinese government. In 2014, the Chinese government elevated smart city construction to a “national strategy”, considering it a cornerstone of China’s future economic and urban development strategies. By 2016, over 500 Chinese cities had initiated or announced smart city pilot construction plans, accounting for nearly half of all such projects planned or underway globally 14. In recent years, with the continuous release of policy benefits related to smart city construction in China and substantial capital investment, China has become a leader in driving global smart city initiatives 15. However, an undeniable fact is that while smart city construction models promote economic development and improve the quality of life for residents, the new infrastructure supporting the operation of smart cities, such as big data centers, 5G shared base stations, and Beidou ground-based augmentation stations, result in substantial energy consumption and significant carbon emissions 16. Research shows that in 2018, the total electricity consumption of data centers in China supporting IT infrastructure reached 160.9 billion kilowatt-hours, exceeding the total electricity consumption of Shanghai for that year and accounting for about 2% of China’s total electricity consumption, with carbon emissions nearing 100 million tons 17. The Environmental Defense Fund (EDF) predicts that by 2035, the total electricity consumption of China’s data centers and 5G base stations will reach 695.1–782 billion kilowatt-hours, accounting for 5–7% of China’s total electricity consumption, with total carbon emissions reaching 230–310 million tons 18.

In 2022, global energy-related CO2 emissions increased by 0.9%, reaching a record high of over 36.8 Gt. Concurrently, atmospheric CO2 concentrations continued to rise, averaging 417.06 parts per million, marking the eleventh consecutive year with an increase exceeding 2 ppm 19. According to the World Meteorological Organization (WMO), the global surface temperature in September 2023 was 1.44 °C higher than the twentieth century average, setting a new historical record 20. The continuous rise in global temperatures has led to frequent occurrences of disastrous events such as extreme heat, torrential rains, floods, forest fires, and hurricanes in recent years, causing significant loss of life and property damage 21. World Health Organization (WHO) data indicates that in 2022, there were at least 29 weather disaster events globally causing billions of dollars in losses, with approximately 61,672 deaths in Europe due to heatwave-related causes 22. As global climate issues become increasingly severe, the call for global carbon emission reduction is growing louder. Cities, as highly concentrated areas of population and economic activities, according to the Global Report by the United Nations Human Settlements Programme (UN-Habitat), consume 60–80% of the global energy and contribute to over 75% of global CO2 emissions 23. As the largest global emitter of carbon, China’s CO2 emissions in 2022 accounted for 27% of the global total 24. Given China’s influence in the global economy, technological innovation, and international cooperation, international organizations and global climate policies generally believe that China’s efforts in carbon reduction are crucial to achieving the global 1.5 °C climate goal 25. In recent years, the Chinese government has actively promoted the construction of low-carbon pilot cities. To date, three batches of low-carbon pilot cities have been implemented in China, bringing the total number of such cities to 81 26.

However, the report “China’s Digital Infrastructure Decarburization Path: Data Centers and 5G Carbon Reduction Potential and Challenges (2020–2035)” indicates that compared to peak carbon emissions expected around 2025 in key sectors like steel, building materials, and non-ferrous metals in China, the “lock-in effect” of carbon emissions from digital infrastructure poses a significant challenge to achieving China’s peak carbon and carbon neutrality goals 27, 28, 29. Given the urgency of global climate change, it raises the question of the correlation between smart cities and low-carbon cities: is it positive, negative, or non-existent? Should the pace of smart city development be slowed to achieve sustainable urban development goals, considering the significant carbon dioxide emissions resulting from current technological choices, social habits, and policy frameworks? To address these practical issues, it is first essential to conduct an objective and accurate assessment of urban SCP and LCL. However, due to the complexity and diversity of urban carbon emissions sources, current measurement and estimation techniques fail to capture all emission types. This limitation hampers the ability to obtain comprehensive, accurate, and timely city-level carbon emission data 30, 31. To address this challenge, this paper decomposes smart cities and low-carbon cities into their interdependent and interactive subsystems (i.e., economic, political, cultural, social, and ecological) viewed through the lens of urban complex systems. It then develops evaluation models for both city types and conducts empirical analyses in 52 representative Chinese pilot cities. Based on these analyses, the paper elucidates the coupling coordination degree between SCP and LCL and proposes a specific pathway for their coordinated development.

This paper is therefore structured as follows: “ Literature review” section offers an overview of the relevant literature, laying the foundation for the introduction of SCP and LCL. Subsequently, SCP and LCL are identified clearly, and measurement based on a mixed method for the coupling coordination degree is established in “ Methodology” section, followed by a case demonstration for the introduced method in “ Results” section and the demonstration results analysis in “ Discussions and implications” section. Finally, “ Conclusions” section summarizes the study’s main findings and contributions, discusses its limitations, and suggests directions for future research.

Literature review

Evaluation of smart city: contents, methods, and subjects

The evaluation of smart cities is a central research area within the smart city development field. Developing standardized evaluation criteria serves the dual purpose of defining smart city development boundaries and scientifically measuring its effectiveness. This, in turn, facilitates the achievement of development goals centered on evaluation-driven construction, improvement, and management 32. We conducted data collection on “smart city*” AND “evaluation”, resulting in the selection of 82 articles. This involved an extensive search of the Wos Core Collection database for articles published in the period from January 2019 to January 2024.

To facilitate a clearer understanding for readers of current research on smart city evaluation, we have categorized it by evaluation contents, evaluation methods, and evaluation subjects.

Cluster1-evaluation contents (what to evaluate), including smart city evaluation dimensions and indicators. By analyzing the article content, it’s clear that most smart city evaluation approaches align with six core dimensions: economy, quality of life, governance, people, mobility, and environment 13, 15. Centered around these six dimensions, international organizations (ISO, ETSI, UN, and ITU) and scholars have established various sets of smart city evaluation indicators, considering the interdependencies among urban economic, environmental, and social factors, all in alignment with the goals of sustainable urban development 32, 33, 34. Notably, Sharifi 35 compiled a comprehensive list of indicators incorporating a wide range of assessment schemes. This list not only covers the scope of the evaluation indicators (project/community/city) and their data types (primary/secondary) but also considers the stages of smart city development (planning/operation) and stakeholder involvement 36. Subsequent research predominantly utilizes the same criteria as Sharifi 35 to identify indicator sets, taking into account the specific needs of each city and defining the spatial and temporal scales of the indicator sets 37.

Cluster 2-evaluation methods (How to evaluate), including smart city evaluation methods and tools. Research in this field focuses on three main areas: identifying evaluation indicators for smart cities, computing composite index, and developing evaluation models 38, 39. Methods for indicator identification mainly include literature review, case studies, brainstorming, the Delphi method, and data-driven techniques 40, 41. The Analytic Hierarchy Process (AHP) is commonly used for calculating composite indices, yet it faces issues like subjective biases and data size limitations 42. Alternative methods, such as the Analytical Network Process (ANP) and the Decision-Making Trial and Evaluation Laboratory (DEMATEL), are used to address these drawbacks by simulating inter-indicator interactions. Additionally, techniques like Principal Component Analysis (PCA) and Data Envelopment Analysis (DEA) are applied for indicator weighting. Finally, smart city evaluation models are constructed to aggregate various dimensions and indicators into a unified score, facilitating project comparison and ranking, and highlighting areas needing improvement 43, 44.

Cluster 3-evaluation subjects (Who performs the evaluation), including smart city stakeholders and participants. Smart city evaluations involve various stakeholders and participants. These complex processes see each entity, including government agencies, international organizations, academic institutions, industry sectors, and NGOs, contributing to the smart cities’ planning, development, and management 45, 46. Key organizations in this realm are the International Organization for Standardization (ISO), International Telecommunication Union (ITU), United Nations Human Settlements Programme (UN-Habitat), Smart Cities Council, European Institute of Innovation and Technology (EIT Urban Mobility), and World Council on City Data (WCCD). Additionally, numerous countries have established their own smart city evaluation standards to direct and review smart city progress 11. Notable examples are the “One New York: The Plan for a Strong and Just City” in the USA, the “BSI PAS 180” in the UK, Singapore's “Smart Nation Initiative”, and China’s “National New-type Smart City Evaluation Indicator System”.

Evaluation of low-carbon city: contents, methods, and subjects

As more countries integrate low-carbon city development into their national strategies and plans, conducting scientific evaluations of cities’ current low-carbon development levels to encourage them to adopt corresponding measures for improvement has become a key strategy in advancing cities towards a low-carbon future 47. In the Wos Core Collection database, we conducted a search for studies spanning January 2018 to January 2023 with “low-carbon city*” AND “evaluation” as keywords, subsequently identifying 98 pertinent articles through two rounds of screening.

This section, maintaining the research framework of “ Evaluation of smart city: contents, methods, and subjects” section (evaluation contents, methods, and subjects), organizes low-carbon city research to enable comparison with smart city evaluations.

Cluster 1-evaluation contents (what to evaluate), including low-carbon city evaluation systems, dimensions, and indicators. Current research focusing on low-carbon cities primarily spans six key domains: urban low-carbon scale, energy, behavior, policy, mobility, and carbon sinks. The evaluation dimensions for low-carbon cities are mainly divided into two types: single-criterion systems concentrating on specific low-carbon aspects (such as low-carbon economy, low-carbon energy, etc.), and comprehensive multi-criteria systems assessing the overall urban low-carbon development 48, 49. Compared to single-criterion evaluation systems, comprehensive and multi-criteria evaluation systems are increasingly gaining attention from scholars. These scholars share the view that low-carbon city construction is a diverse, dynamic, interconnected process that requires comprehensive consideration of various urban aspects, including economy, society, and environment, and involves coordinating the actions of different stakeholders to achieve sustainable urban development 50, 51. Additionally, international institutions and many national governments have also published low-carbon city evaluation frameworks from the perspective of comprehensive and multi-criteria evaluation systems. The most notable examples include the United Nations Commission on Sustainable Development, which set 30 indicators from four dimensions: social, environmental, economic, and institutional, to evaluate the level of urban low-carbon development. The Chinese Academy of Social Sciences proposed the “China Low Carbon City Indicator System”, covering 8 dimensions such as economy, energy, facilities, and 25 specific indicators including energy intensity, per capita carbon emissions, and forest coverage rate.

Cluster 2-evaluation methods (How to evaluate), including low-carbon city evaluation methods and tools. Firstly, identifying evaluation indicators as the initial step in constructing a low-carbon city evaluation model, current research methods not only include traditional methods like literature review and expert interviews but also increasingly involve scholars using dynamic perspectives based on urban complex systems, applying models like DPSR (Driving forces-Pressures-State-Response), STIRPA (Stochastic Impacts by Regression on Population, Affluence, and Technology), the Environmental Kuznets Curve (EKC), and STEEP (Social, Technological, Economic, Ecological, and Political) for indicator identification 52, 53. Secondly, weighting evaluation indicators, an essential part of model construction, typically involves methods like subjective weighting (expert scoring, Delphi method, AHP) 54, objective weighting (PCA, Entropy weight method, variance analysis), and combined weighting (DEA) 55. Each method has its characteristics and suitable scenarios and should be selected according to specific circumstances. Additionally, quantitative assessment of regional carbon emissions using methods like carbon footprint analysis, baseline emission comparison, and Life Cycle Assessment (LCA) is also becoming a research focus 56.

Cluster 3-evaluation subjects (Who performs the evaluation), including low-carbon city stakeholders and participants. The evaluation of low-carbon cities also involves multiple stakeholders (government, enterprises, residents, etc.) 57. Among them, international organizations like the International Organization for Standardization (ISO), the International Energy Agency (IEA), and the World Meteorological Organization (WMO) have played significant roles in establishing low-carbon city evaluation standards and promoting global low-carbon city development. Additionally, due to economic, policy, and perception factors, current low-carbon city construction relies primarily on government financial input, with social capital and public participation in low-carbon city construction noticeably lacking 58. Therefore, how to enhance the awareness of enterprises and residents as main actors in low-carbon city construction has become a current research focus.

Coupling coordination analysis between SCP and LCL

Smart cities and low-carbon cities, as important urban development models for the future, have seen an increasing focus on their interrelation by scholars in recent years, becoming an emerging research hotspot in the field. In the Wos Core Collection database, we searched for studies from January 2018 to January 2024 using the keywords “smart city*” “low-carbon city*” “correlation analysis” “coupling coordination analysis” and “urban sustainability”. After two rounds of screening, 24 related studies were selected for analysis.

From the perspective of research results, the current research conclusions about the correlation between low-carbon cities and smart cities primarily include two main points: (i) SCP and LCL cannot achieve coupling coordination development. Some scholars argue that SCP and LCL differ in their focus: SCP emphasizes urban technological and economic development, while LCL focuses more on urban ecological construction 17. Particularly, De Jong identified 12 urban development concepts, including smart city, low-carbon city, eco-city, and green city. He believes that a clear distinction must be made in the conceptual definition of these types of cities to more accurately guide future urban planning 59. Furthermore, some scholars argue that the relationship between SMC and LCC is negatively correlated. Deakin believes that the direct environmental benefits of IoT technology are insufficient to achieve urban sustainability goals 60. Barr et al. argue that the logic of smart cities often leads city administrations to prioritize superficial changes and promote individual behavioral shifts, detracting from the crucial task of reconfiguring urban infrastructure for low-carbon lifestyles 61, 62. (ii) SCP and LCL can achieve coupling coordination development. Some scholars believe there is a positive correlation between SCP and LCL, with SCP potentially promoting the development of LCL. Specifically, the intelligent systems built by SCP can effectively match urban energy supply and demand, reducing urban carbon emissions, such as through smart grids and intelligent transportation networks 18. It is worth noting that most of the studies on the coupling coordination relationship between urban SCP and LCL are based on perspectives of individual urban subsystems such as technology, economy, management, industrial structure, and society. They lack a comprehensive consideration of the city as a complex system 59, 61, 63.

From the perspective of research methodologies, coupling coordination analysis is a fundamental statistical approach for examining relationships between two or more variables. This analysis typically employs techniques such as Pearson’s correlation coefficient, Spearman’s rank correlation coefficient, Kendall’s tau, partial correlation, point-biserial correlation, and multiple correlations. Each technique offers unique insights into the nature and strength of the interdependencies among variables 61. The selection of an appropriate method depends on the data type (continuous, ordinal, or categorical), its distribution (e.g., normal distribution), and the specific objectives of the research.

In summary, although existing research has made significant contributions to the independent evaluation and advancement of smart cities and low-carbon cities, including their relevant construction content, main actors, as well as some specific measures such as empowering cities with data intelligence for low-carbon economic development and transitioning industrial structure to low-carbon, there are still some important knowledge gaps. On the one hand, current research primarily analyzes the coupling coordination relationship between urban SCP and LCL from the micro-perspective of individual urban subsystems such as economic and energy systems. This approach lacks a macroscopic perspective from the complex urban system, which is detrimental to the comprehensive development of cities 60, 64, 65. On the other hand, current studies often only conduct basic qualitative comparisons of the relationship between the development levels of urban SCP and LCL from a quantitative or qualitative perspective. They lack a comprehensive analytical approach that integrates both qualitative and quantitative analyses for further exploration of the coupling coordination relationship between urban SCP and LCL. This shortfall hinders the sustainable development of cities.

To fill these knowledge gaps, this study employs a mixed-methods approach, combining qualitative and quantitative analyses, to examine the model of coupling coordination between urban SCP and LCL. It also develops recommendations to enhance this coupling coordination, aiming to support sustainable development goals. Furthermore, this research selects 52 typical low-carbon and smart pilot cities in China as case studies, ensuring both scientific validity and practical applicability of the findings. Additionally, to enhance the logical coherence and readability of this study, we posit that a coupling coordination relationship exists between urban SCP and LCL and thus propose Hypothesis 1.

Hypothesis 1

There is a substantial degree of coupling coordination between the overall urban system’s SCP and LCL, yet there are disparities in this coordination degree among the subsystems of economy, society, politics, culture, and ecology.

Methodology

Research framework

The construction of low-carbon and smart cities, as key pathways to urban sustainability, necessitates examining their interplay and fostering their collaborative development for achieving sustainability goals 66. This research employs a sequential framework, including Conceptual, Data, Analysis, and Decision-making Layers, to methodically explore the coupling coordination relationship between SCP and LCL, with the framework illustrated in Fig. 1.

Research framework.

Firstly, in the Conceptual Layer, this study aligns with the United Nations’ objectives for sustainable cities, encompassing economic growth, social equity, better life conditions, and improved urban environments. Integrating these with China’s “Five-Sphere Integrated Plan (economy, politics, culture, society, and ecological environment construction)” for urban development, the research dissects the components of smart city systems (such as information infrastructure, information security, public welfare services) and low-carbon city systems (including low-carbon construction, transportation, and industry), with the aim to collect indicators. Secondly, in the Data Layer, this research develops smart city and low-carbon city evaluation systems, grounded in national standards and official statistics, to qualitatively examine the correlation between SCP and LCL from a macro perspective. Thirdly, in the Analysis Layer, this study selects 52 cities, both smart and low-carbon pilot cities in China, as samples for quantitative analysis. The process involves standardizing indicators, scoring and ranking the cities based on their smart performance and low-carbon levels, followed by employing Pearson’s correlation coefficient and coupling coordination degree model to scientifically analyze the correlation between SCP and LCL. Finally, in the Decision-making Layer, the study examines the coupling coordination relationship between urban smart performance, the overall low-carbon level, and the low-carbon level across five dimensions, which is key for us to test Hypothesis 1. It also formulates development paths for the coupling coordination of smart and low-carbon cities.

SCP index system construction

Since the concept of smart cities was introduced in 2008, many national governments have established smart city evaluation standards. Due to varying national conditions, SCP evaluation indicators differ across countries. As the sample cities in this study are Chinese smart pilot cities, the selection of SCP evaluation indicators primarily references relevant Chinese national standards. As a global pioneer in smart city development, China released the “Evaluation indicators for new-type smart cities (GB/T 33356-2016)” in 2016 and revised it in 2022. This national standard, with its evaluative indicators, clearly defines the key construction content and development direction of new smart cities, aiming to specifically enhance the effectiveness and level of smart city construction, gaining significant recognition within the industry.

This study, grounded in the concept of a city’s “Five-in-One” sustainable development, is guided by three principles of “Inclusive well-being & Ecological harmony”, “Digital space & Physical space”, and “New IT technologies & Comprehensive services”. It also adheres to the “people-oriented concept” and adopts an “urban complex dynamic perspective” in the process of smart city construction. Additionally, it follows the principle of “similar attributes of evaluation objects”. Based on these foundations, the study establishes three criteria for selecting evaluation indicators, including scientific, coordination, and representation. Drawing on the Chinese government’s smart city evaluation standards and utilizing a literature review methodology, this research constructs an SCP evaluation indicator system for cities, as detailed in Supplementary Appendix Table A1. The SCP index system includes six primary indicators, including smart public service (SPE), precise governance (PG), information infrastructure (II), digital economy (DE), innovative development environment (IDE), and citizen satisfaction (SCS). It also features 24 secondary indicators, such as traffic information services, grassroots smart governance, and spatio-temporal information platforms. Importantly, to explore the correlation between smart cities and low-carbon cities more effectively, the study deliberately omits “Internet + Green Ecology” related indicators from the smart city evaluation system. To ensure the accuracy and representativeness of these indicators, they were validated through expert consultation, public participation, and comprehensive statistical methods.

LCL index system construction

Current international organizations and academic perspectives on low-carbon city evaluation systems are predominantly based on the urban complex systems approach, considering the interplay and interaction of aspects such as low-carbon society, economy, and technology. Consistent with the principles for selecting SCP evaluation indicators, the choice of LCL evaluation indicators in this study primarily adheres to relevant Chinese national standards and related literature.

As a proactive practitioner in global low-carbon city development, in 2021, the Chinese government released the “Sustainable Cities and Communities—Guides for low-carbon development evaluation (GB/T 41152-2021)”. This national standard evaluates the level of urban low-carbon development, clarifying the key directions for such development, and serves as a current guide for low-carbon city construction in China. Thus, this study, grounded in the “Five-in-One” sustainable urban development framework and guided by the principles of “carbon reduction & pollution reduction”, “green economic growth”, and “enhanced carbon sequestration capacity”, combines the previously established principles of scientific, coordination, and representative for selecting evaluation indicators. It establishes an LCL index system based on the Chinese government’s evaluation standards and relevant literature. Specifically, the LCL evaluation index system constructed in this study includes five primary indicators, including low-carbon economic (LCE), low-carbon society (LCS), low-carbon environmental quality (LCEQ), low-carbon management (LCM), and low-carbon culture (LCC), as well as 22 secondary indicators such as energy consumption per unit of GDP and carbon emission intensity, as shown in Supplementary Appendix Table A2. Similarly, to ensure the accuracy and representativeness of the indicators, the specific indicators were validated through expert consultation, public participation, and comprehensive statistical methods.

Analysis model construction

In this study, an Entropy-TOPSIS-Pearson correlation-Coupling coordination degree (ETPC) analysis model is constructed to quantitatively analyze the coupling coordination relationship between Urban SCP and LCL. The entropy method is first applied for objective weighting of evaluation indices, ensuring data objectivity and reducing subjective bias, thus enhancing the model’s accuracy and fairness. Next, the TOPSIS method is used to rank sample cities based on their smart performance and low-carbon levels, providing a straightforward and intuitive ranking mechanism. The Pearson correlation method then examines the correlation between SCP and LCL, offering data-driven insights into the dynamic relationships between these variables. Finally, the coupling coordination model calculates the degree of coordination between SCP and LCL, providing a theoretical basis for subsequent enhancement pathways and policy recommendations. The ETPC model constructed in this study has several advantages and complementarities, allowing for a comprehensive analysis and evaluation of the research question from various perspectives. Additionally, the ETPC model can be broadly applied to other multidimensional evaluation and decision analysis issues, such as the coupling coordination between various public health interventions and community health levels, and the comprehensive effects of different economic policies on regional economic development and environmental impact. Specific analysis steps are outlined as follows.

Step 1: Conduct the data normalization process.

where xij and yij represent respectively the original and standardized value for the indicator j in referring to the sample case i (i = 1,2,3,…,m; j = 1,2,3,…,n), max(xj) and min(xj) denote respectively the largest and smallest value among all m samples for the indicator j, Pij represents the value proportion of indicator j in the sample case i to the summation value of the indicator from all cases.

Step 2: Calculate the weight and measure the comprehensive level based on entropy method.

The entropy weight method, an objective approach deriving weights from sample characteristics, mitigates expert bias, enhancing the objectivity and credibility of indicator weighting 67. This study employs this method, determining weights through the calculation of each indicator’s information entropy, and measure the comprehensive level of the subsystem.

where m is the total number of sample cases, \({e}_{j}\) demonstrates the entropy value of the j indicator and \({\omega }_{j}\) denotes the weight of indicator j, and V represent the comprehensive level.

Step 3: Conduct a ranking of evaluation objects based on TOPSIS method.

A key limitation of the entropy method is its tendency to neglect the significance of indicators. The TOPSIS method, addressing this issue, is an ideal-solution-based ranking technique that aids in multi-objective decision-making among finite options 68. In this approach, the study first determines positive and negative ideal solutions, measures each objective’s distance to these ideals, and subsequently ranks the subjects by the proximity of each objective to the ideal solution.

where \({ V}^{+}\) and \({V}^{-}\) respectively represent the best ideal solution and the worst ideal solution, \({D}_{i}^{+}\) and \({D}_{i}^{-}\) represent the distances from the objective to the positive and negative ideal solutions, respectively. \({C}_{i}\) indicates the closeness of the evaluation objective to the optimal solution, with \({C}_{i}\in \left[\text{0,1}\right]\). A larger \({C}_{i}\) value suggests stronger smart and low-carbon development capabilities of the sample city.

Step 4: Analyze the correlation based on Pearson correlation method.

The Pearson correlation method is commonly used to measure the correlation coefficient between two continuous random variables, thereby assessing the degree of correlation between them 69. In this study, based on the results from Steps 1–3, two sets of data are obtained representing the smart development level and low-carbon development level of sample cities, \(A:\left\{{A}_{1},{A}_{2},\dots ,{A}_{n}\right\}\) and \(B:\left\{{B}_{1},{B}_{2},\dots ,{B}_{n}\right\}\). The overall means and covariance of both data sets are calculated, resulting in the Pearson correlation coefficient between the two variables.

where \({A}_{i}\) and \({B}_{i}\) respectively represent the SCP and LCL of sample cities. \(E\left(A\right)\) and \(E\left(B\right)\) are the overall means of the two data sets, \({\sigma }_{A}\text{ and }{\sigma }_{B}\) are their respective standard deviations, \(cov(A,B)\) is the covariance, and \({\rho }_{AB}\) is the Pearson correlation coefficient. When the correlation coefficient approaches 0, the relationship weakens, as it nears − 1 or + 1, the correlation strengthens.

Step 5: Analyze the coupling coordination degree based on the coupling coordination model.

The coupling coordination degree characterizes the level of interaction between different systems and serves as a scientific model for measuring the coordinated development level of multiple subsystems or elements 70. This study has developed a model to measure the coupling coordination degree between two systems.

where C defines the coupling degree, \({f}_{1}\) and \({f}_{2}\) are the evaluation values of SCP and LCL respectively. CPD represents the coupling coordination degree. \(\alpha\), \(\beta\) are the coefficient to be determined, indicating the importance of the systems. This study assumes that each system is equally important. Thus \(\alpha =\beta =1/2.\)

In this study, building upon the framework established by a preceding study, a classification system for the coupling coordination degree was developed. This system delineates the various types of coupling-coordinated development among SCP, LCL, LCS, LCM, LCEQ, and LCC. Current research on the division of coupling coordination degree intervals often uses an average distribution within the [0, 1] range 70. However, due to the large sample size and the wide distribution range of coupling coordination degrees in this study, we have categorized these types into ten distinct levels based on their rank, as detailed in Table 1.

Selection of sample cities and data collection

The Chinese government has prioritized the development of smart and low-carbon cities. Since 2010, it has launched 290 smart city pilots and 81 low-carbon city pilots across various regions, reflecting different levels of development, resource allocations, and operational foundations. To maintain the scientific integrity of our study, we established stringent criteria for selecting sample cities: (i) each city must be concurrently identified as both a smart and a low-carbon city pilot, and (ii) their government agencies must have issued data on key performance indicators for these initiatives. Following these criteria, our research has ultimately selected 52 cities as samples, as detailed in Fig. 2. It is noteworthy that these 52 typical case cities are almost all provincial capitals in China, mostly located within the Yangtze River Delta, Pearl River Delta, Jingjinji (Beijing–Tianjin–Hebei), and Western Triangle economic regions. Additionally, according to the “Globalization and World Cities Research Network (GaWC) World Cities Roster 2022 (GaWC2022)”, these cities are ranked within the top 200 globally. Therefore, given the scope of this research, these case cities offer significant representativeness and can serve as valuable models for promoting development in other urban areas. The data for this paper were sourced from the “China Low-Carbon Yearbook (2010–2023)”, the “China Environmental Statistics Yearbook (2010–2023)”, and low-carbon city data published by the governments of the sample cities. Additionally, this study addressed any missing data by averaging the data from adjacent years and applying exponential smoothing.

52 sample cities and their geographic locations.

Results

Weighting values between evaluation indicators

The entropy weighting values between the 20 indicators of SCP and the 19 indicators of LCL are calculated by applying the data described in “ Weighting values between evaluation indicators” section to formula ( 1)–( 5), and the results are shown in Supplementary Appendix Tables A3 and A4. Specifically, within the SCP evaluation framework, SPE and II are assigned the highest weights, while LCS and LCM are allocated the highest weights within the LCL evaluation framework. Conversely, SCS and LCC have attributed the lowest weights in their respective contexts.

Evaluation of SCP and LCL in sample cities

Utilizing the data from “ Selection of sample cities and data collection” section and the weighting values derived in “ Weighting values between evaluation indicators” section, we can determine the SCP and LCL of sample cities using the TOPSIS method, as outlined in formulas ( 6)–( 9). The results are illustrated in Supplementary Appendix Table A5 and Fig. 3. In this study, the value of the closeness coefficient (Ci) is used to indicate the relative closeness of a particular sample city to the negative ideal point 71. The negative ideal point represents the worst solution of the ideal, where the individual attribute values reach their worst in each alternative. Therefore, a larger value of closeness indicates better smart city performance or a lower carbon level of a sample city 72. CLCL and CSCP respectively represent the low-carbon level closeness coefficient and the smart city performance closeness coefficient. In referring to Supplementary Appendix Table A5, the best three cities of SCP are Shenzhen, Shanghai, and Hangzhou, whilst the worst three cities are Yan’an, Jincheng, and Xining. Furthermore, Chengdu, Qingdao, and Beijing are the best there low-carbon level performers. Whilst Jincheng, Urumqi, and Huhehaote are the three worst.

TOPSIS-based analysis of SCP with LCL in 52 sample cities.

In referencing Fig. 3, this study considers SCP data of sample cities as the control variable and ranks them in ascending order based on TOPSIS results. We then examine changes in LCL data to ascertain the correlation between these variables, yielding two key research conclusions: on one hand, analysis of 52 sample cities demonstrates a general ascending trend in both SCP and LCL data curves. This trend suggests a positive correlation between these two parameters. On the other hand, the LCL data, in contrast to the consistent rise in SCP, exhibits notable fluctuations and wider dispersion. This indicates that the positive correlation between SCP and LCL, while present, is not markedly robust.

Correlation results of SCP and LCL in sample cities

1. (1)
Correlation analysis of urban SCP and overall-LCL. This analysis employs the closeness coefficient (Ci) to assess SCP and overall-LCL in sample cities for Hypothesis
1 in Eqs. ( 10) and ( 11). The results are presented in Table 2. Additionally, a linear regression analysis is conducted to determine the presence and magnitude of the relationship between SCP and LCL in these cities, as shown in Fig. 4.

The scatter and regression of SCP and LCL: (A) SCP & Overall-LCL; (B) SCP & LCM; (C) SCP & LCS; (D) SCP & LCE; (E) SCP & LCQE; (F) SCP & LCC.

Considering the closeness coefficient range, correlation is categorized into five levels: very weak (\(\left|{\rho }_{AB}\right|<0\).1), weak (\(0.1\le \left|{\rho }_{AB}\right|<0\).3), moderate (\(0.3\le \left|{\rho }_{AB}\right|<0\).5), strong (\(0.5\le \left|{\rho }_{AB}\right|<0\).7), and very strong (\(0.7\le \left|{\rho }_{AB}\right|<1.0\)) 73. Table 1 indicates a strong positive correlation between SCP and overall LCL. Linear regression analysis in Fig. 4 A demonstrates a significant correlation between SCP and urban LCL (R2 = 0.42, p < 0.001), with notable differences exist among cities, consistent with Hypothesis 1.

1. (2)
Correlation analysis of SCP and each low-carbon dimension. Pearson correlation analysis effectively measures the strength of linear relationships between two variables, but it does not identify causal relationships between them. To address this limitation and explore the interaction between the two variables, this study sets and solves the closeness coefficient for each low-carbon dimension, which are low-carbon economy (CLCE), low-carbon society (CLCS), low-carbon environmental quality (CLCEQ), low-carbon management (CLCM), and low-carbon culture (CLCC). It then calculates the correlation analysis results for SCP and each low-carbon dimension for Hypothesis
1, as shown in Table 4.

In detail, strong correlations exist between SCP and LCM, LCS, and LCEQ. The correlation is moderate with LCE and weak with LCC. Furthermore, linear regression analysis shows that the links between SCP and low-carbon levels across five dimensions are significant with minimal variance. Cities with higher SCP typically show higher values in LCM (R2 = 0.38, p = 0.000), LCS (R2 = 0.35, p = 0.000), and LCE (R2 = 0.32, p = 0.000) as depicted in Fig. 4 B–D. However, this trend is less pronounced in LCEQ (R2 = 0.17, p = 0.000) and LCC (R2 = 0.06, p = 0.001), which exhibit greater dispersion as shown in Fig. 1 is robust.

Coupling coordination degree of SCP and LCL in sample cities

The degree of coupling coordination comprehensively considers multiple aspects of urban complex systems, including economic, social, and environmental dimensions. By systematically evaluating the coordinated development level of urban SCP and LCL, this approach enables the analysis of the coupling and coordination relationships between SCP and LCL, as well as among various subsystems such as LCM, LCS, LCE, LCEQ, and LCC. This reveals the dynamic interactions and causality between SCP and LCL within urban complex systems. The coupling coordination degrees of SCP and LCL, along with their subsystems, in 52 typical smart and low-carbon pilot cities in China, are illustrated in Fig. 5.

Coupled coordination degree of SCP and LCL, LCS, LCEQ, LCE, LCM, LCC.

1. (1)
Characteristics of objective changes in the coupled coordination degree between SCP and LCL. Based on the coupling coordination model and Eqs. (
12) to ( 14), the coupling coordination degree of the urban complex system in SCP and LCL regions is calculated for Hypothesis 1, as illustrated in Fig. 5.

From the holistic perspective of urban complex systems, as the level of urban SCP continuously improves, the coupling coordination degree between SCP and LCL among 52 pilot cities in China shows an upward trend. This indicates that as the functional indices of urban SCP and LCL both strengthen, their interaction and coordination also enhance. Among these, Jincheng has the lowest coupled coordination degree at 0.5201, while Beijing boasts the highest at 0.8622. Within the 52 pilot cities, 5.78% exhibit a barely coupling coordination level, 51.93% display a primary coupling coordination level, 25% achieve an intermediate coupling coordination level, and 17.31% reach a good coupling coordination level. Moreover, the average coupling coordination degree of the 52 pilot cities is 0.598, suggesting that the SCP and LCL of the pilot cities can achieve coupled coordinated development.

1. (2)
Characteristics of objective changes in the coupled coordination degree among SCP, LCM, LCS, LCE, LCEQ, and LCC for Hypothesis
1 are illustrated in Fig. 5.

From the perspective of urban subsystems, the coupling coordination degrees of LCS & SCP, LCE & SCP, and LCM & SCP all exhibit characteristics of steady fluctuations with an upward trend, while the coupling coordination degree of LCC & SCP shows greater volatility in its upward trend. The coupling coordination degree of LCEQ & SCP demonstrates a trend of initially rising and then declining. Furthermore, the average values of the coupling coordination degrees for LCS & SCP, LCE & SCP, LCM & SCP, LCEQ & SCP, and LCC & SCP are 0.478, 0.761, 0.779, 0.710, and 0.485, respectively. Among these, the pilot cities’ subsystems of LCE, LCM, and LCEQ with SCP exhibit an intermediate level of coupling coordination, while the coupling coordination degrees of LCS and LCC with SCP are on the verge of a dysfunctional recession. This indicates that the causal relationships between urban SCP and the subsystems of urban LCM, LCS, LCE, LCEQ, and LCC vary. Overall, Hypothesis 1 holds true both from the perspective of the city's overall system and from the perspective of its various subsystems.

Discussions and implications

Relationship between SCP and LCL of different cities

Considering the evaluation results of the urban SCP and LCL, four grades of the overall points can be classified, namely, excellent (0.7–1.0), average (0.5–0.7), below average (0.4–0.5), and poor (0–0.4). Subsequently, the sample cities in Supplementary Appendix Table A5 were classified based on these gradations. In the sample, cities with excellent SCP constitute 9.62%, about double the proportion with excellent LCL. Cities with average SCP account for 48.08%, whereas those at average LCL represent only 26.92%. Notably, cities with poor LCL comprise 26.92%, nearly triple the rate of those with poor SCP. The findings suggest that China’s SCP currently outperforms its low-carbon city initiatives, largely attributable to the rapid advancement of the Internet and Information and Communication Technology (ICT) in recent years. What’s more, Fig. 4 illustrates that urban SCP significantly positively influences the urban LCL, though substantial variations exist among different cities. The relevant types can be summarized into the following four categories.

Quadrant I-high SCP and high LCL, including only six cities (Shenzhen, Shanghai, Beijing, Ningbo, Xiamen, and Qingdao). These cities are not only among China’s earliest smart city pilots but also recent focus areas for the government’s “Carbon Peak Pioneer Cities” initiative. By actively exploring innovative models, systems, and technologies for smart and low-carbon co-development, these cities provide valuable practical experiences for others. For instance, Shenzhen has developed a multi-level, multi-component greenhouse gas monitoring network and technology system for “carbon flux, carbon concentration, carbon emissions”, while Ningbo has constructed a “smart zero-carbon” comprehensive demonstration port area.

Quadrant II-poor SCP and poor LCL, numerous cities in Fig. 4 A, such as Jincheng, Lhasa, and Urumqi, exhibit poor SCP and LCL. Despite China having the most smart and low-carbon city pilots globally, its development level in these areas still lags significantly behind typical developed countries. While China’s infrastructure like networking and computing power has reached a certain scale, issues persist with insufficient integration and intensity in infrastructure construction and operation, as well as problems with aging infrastructure and low levels of intelligence. Furthermore, although China’s low-carbon pilot cities have made positive progress in promoting low-carbon development, most still have incomplete carbon emission statistical systems and inadequate operational mechanisms, leading to generally poor overall low-carbon development levels.

Quadrant III-high LCL but poor SCP, such as Kunming, Xining, and Guiyang. These cities possess resources conducive to low-carbon development, such as Kunming and Guiyang with their rich forest carbon sinks, and Xining with abundant clean energy sources like solar and wind power. However, they are mostly situated in China’s central and southwest areas with underdeveloped physical and economic conditions. Leveraging their abundant low-carbon resources, and utilizing big data and IoT technology, achieving sustainable green economic growth through carbon credits and trading markets, as well as green finance, represents a significant future development direction for these cities.

Quadrant IV-high SCP but poor LCL, including Suzhou, and Jinhua Zhongshan, decoupling economic development from carbon emissions presents a significant development challenge for these cities. Specifically, for Suzhou, one of the world’s largest industrial cities, the main challenge is achieving decarburization in the energy sector and transitioning high-emission manufacturing industries to low-carbon alternatives.

What’s more, as illustrated in Fig. 5, the degree of interaction between SCP and LCL across the 52 pilot cities in China positively impacts the balanced and comprehensive performance of these cities. This, in turn, fosters the coordinated development of urban systems as a whole. Moreover, the continual increase in the coupled coordination degree between SCP and LCL with the enhancement of SCP in pilot cities indicates that smart city construction contributes to urban low-carbon development. Future urban development in China should fully leverage the industrial upgrading effect, carbon sequestration effect, and energy utilization effect of smart city construction. However, the increasing slope of the SCP & LCL coupled coordination degree curve in Fig.

Relationships between SCP and LCL in each urban subsystem

The relationship between urban SCP and LCL across five dimensions is illustrated in Fig. 4 B–F. There is a strong positive correlation between SCP and LCM, LCS, and LCE, while a moderate correlation is observed with LCEQ, and a weak correlation with LCC. Furthermore, the degree of coupling coordination between SCP and subsystems such as LCS, LCEQ, LCE, LCM, and LCC is examined in Fig. 5. The results of the coupling coordination vividly illustrate the synergistic interactions and developmental harmony between urban SCP and various systems.

Among these, the coupling coordination degree curve fluctuation between SCP & LCM is stable, situated at an intermediate coupling coordination level, indicating the dominant role of the Chinese government in the construction of smart cities and low-carbon cities, as well as the effectiveness of policy implementation. However, this also suggests that in promoting urban smart and low-carbon construction, China faces the risk of adopting “one-size-fits-all” mandatory policies, neglecting to advance construction in phases with emphasis, tailored to the city's resource endowment and economic development status. The coupling coordination degree curve changes between SCP&LCE and SCP&LCL show the highest degree of fit, indicating that low-carbon economic development brought about by digital empowerment and upgrading of the urban industrial structure is a key driving factor for promoting the coupled coordination development of urban smart and low-carbon initiatives. Transforming traditional industrial structures and pursuing low-carbon upgrades of the economic structure present challenges for urban development in China today. The coupled coordination degree of SCP & LCS is on the verge of a dysfunctional recession, highlighting the imbalance in the development between China's SCP and LCS, especially in terms of new infrastructure construction, such as smart transportation and logistics facilities, smart energy systems, smart environmental resources facilities, etc. The current construction of new infrastructure in China is far from meeting the living needs of the broad masses of people.

It is noteworthy that with the continuous improvement of the SCP in sample cities, the coupling performance degree between SCP and LCEQ exhibits two phases: an initial stage of synergistic enhancement followed by a stage of diminished synergy. In the early phase of synergistic development, the SCP and LCEQ systems of cities, driven by shared goals of sustainable urban development, strategy adjustments, resource sharing, and technological progress, facilitated effective collaboration and integration between systems. However, upon reaching a certain stage, intensified resource competition, declining management efficiency, and environmental changes led to internal system fatigue, resulting in weakened synergy. This indicates that once the technological effects generated by smart city construction reach a certain level, it becomes crucial to enhance the city's capacity for autonomous innovation. Addressing the bottleneck issues of core technologies and transforming the development mode of smart low-carbon technology from “imitative innovation” represent significant breakthroughs for further promoting the coupled coordination of SCP and LCEQ in China’s future.

Moreover, as the SCP of sample cities continuously improves, the coupled coordination degree between SCP and LCC shows two phases: initial stable fluctuations and subsequent rapid growth. The turning point in the curve change occurs at a coupled coordination degree of 0.6, denoted as the primary coupling coordination point. Among these, the low-carbon awareness rate of urban residents, as a key indicator of LCC, shows that the majority of urban residents in China are still in the cognitive awakening stage regarding low-carbon consciousness. At this stage, residents begin to recognize the severity of climate change and environmental degradation, along with the importance of smart low-carbon lifestyles in mitigating these issues. The government continuously promotes this awareness through media reports, educational activities, official propaganda, and community initiatives. As residents gain a deeper understanding of the issues, their attitudes shift from initial indifference or skepticism to a stronger identification with and support for the values and concepts of smart low-carbon living. This shift encourages residents to experiment with new smart low-carbon lifestyles, gradually finding suitable smart low-carbon behavioral patterns that become habitual. Ultimately, when smart low-carbon lifestyles are fully internalized as part of residents’ values, they not only practice smart low-carbon living at the individual level but also actively participate in promoting society’s smart low-carbon construction. Therefore, this study posits that the emergence of the coupled coordination degree turning point between SCP and LCC is not only a process of individual behavioral change but also a reflection of social and cultural transformation. This process is time-consuming and influenced by multiple factors, including policy guidance, economic incentives, educational dissemination, and the social atmosphere.

Implications for promoting coupling coordination development between urban SCP and LCL

Low-carbon and smartness are vital features of modern, sustainable urban development and key supports for it. This study posits that urban low-carbon and smart development should not be disjointed but rather synergistic and complementary. To better achieve sustainable urban development goals, a model should be constructed with “low-carbon” as the cornerstone of sustainable development and “smartness” as the technological assurance for low-carbon growth. Specifically, this study proposes the “urban smart low-carbon co-development model”, which entails a deep integration of intelligent technologies such as the Internet of Things (IoT) and big data with urban construction, governance services, and economic development. This model leverages digitalization to facilitate decarburization, thereby achieving urban sustainable development goals such as energy-efficient and green urbanization, ecological and livable environments, and streamlined governance services.

Furthermore, to better coordinate smart development with low-carbon city construction, enhance low-carbon city building through digitalization, and explore exemplary practices and models of smart low-carbon city construction, this study finds it necessary to establish an evaluation system for smart and low-carbon urban co-development. Therefore, based on the aforementioned urban SCP and LCL evaluation indicator system, this study initially conducted a literature review of past research, selecting 5 primary indicators and 20 secondary indicators from 48 articles to evaluate the degree of coupling coordination development between urban SCP and LCL. Subsequently, the Delphi method was employed to finalize the list of evaluation indicators, with 10 experts from various regions and diverse backgrounds in China refining the list and determining the weights of each indicator, as shown in Supplementary Appendix Table A6. The final Smart Low-Carbon City Coupling Coordination Development Evaluation Indicator System, as presented in Table 3, comprises 5 primary indicators and 18 secondary indicators. This evaluation system aims to emphasize the utilization of next-generation information technologies such as 5G, artificial intelligence, cloud computing, and blockchain to expand urban green ecological spaces, strengthen ecological environment governance, and enhance the level of intelligent urban governance, meeting the development needs of smart low-carbon cities.

The policy implications from the analysis results suggest that actions should be taken by government departments in China to reduce the uneven performance between urban SCP and LCL across various cities. These actions include, for example: Firstly, guiding the innovative development of urban SCP and LCL through policies, such as enhancing government digital services and administrative platforms, continuously promoting the development of emerging industries and the upgrading of traditional industries, and actively promoting green energy technologies. Secondly, categorizing and advancing the coordinated development of smart and low-carbon cities—comprehensive development should be pursued simultaneously in large cities in eastern and central China, while in smaller cities in western China, priorities should include enhancing urban innovation capabilities and improving infrastructure to lay a solid foundation for the coupled coordination of urban SCP and LCL. Thirdly, constructing a multi-stakeholder governance system to maximize the leading role of the government, the main role of enterprises, and the active participation of residents. By fostering a positive social atmosphere and cultural attributes, this will enhance the sense of participation and achievement among different social groups, creating a sustainable development model for urban SCP and LCL coordination. Lastly, emphasizing the development of SCP and LCL coordination in county-level cities is crucial. While large Chinese cities have already begun to form a pattern of coordinated SCP and LCL development, county-level cities, though with weaker infrastructures, possess tremendous potential. Focusing on low-carbon production, circulation, and consumption, and strengthening smart and low-carbon constructions in county-level cities will be a vital task for future urban development in China.

Conclusions

The global urbanization process brings opportunities for economic growth and social development, but also presents a series of challenges, such as environmental pressures and resource constraints 3. The evaluation of urban SCP and LCL creates a link between the policy-making in urban resources environment management and the objectives of sustainable development goals (SDGs 11.4, 11.6, and 11.b) at the city level 74. Currently, there is no unified consensus on the coupling coordination development between urban SCP and LCL. This study proposes a method combining qualitative and quantitative analysis from the perspective of urban complex systems to analyze the coupling coordination relationship between SCP and LCL. This new method clearly interprets a strong positive correlation between urban smart performance and the overall low-carbon level. Specifically, there are strong correlations between SMC and LCM, LCS, and LCE, with a moderate correlation to LCQE and a weak correlation with LCC. Several innovative insights for this method are highlighted: (i) sustainable development based on SCP and LCL assessment; (ii) emphasizing the “people-centric” concept in urban development; (iii) analyzing from the perspective of urban complex systems.

This study selected 52 typical smart and low-carbon pilot cities in China as sample cities to analyze the coupled coordination relationship between urban SCP and LCL. And the main findings from this analysis can be summarized as follows: (i) smart city initiatives outperform low-carbon city development, with notable differences in SCP and LCL effectiveness across eastern, central, and non-resource-based cities versus western, peripheral, and resource-dependent ones in China. (ii) A strong positive link between urban SCP and low-carbon levels, especially between SCP and LCM, LCS, and LCE, with moderate and weak correlations to LCEQ and LCC, respectively. (iii) An increasing urban SCP levels enhance the coupling coordination within the urban SCP and LCL system. SCP & LCE, SCP & LCM, and SCP & LCS subsystems align well with the overall system, driving the coupled coordination of urban SCP and LCL. In contrast, SCP & LCC and SCP & LCEQ have lesser alignment, affected by factors like technology, policy, economic incentives, education, and societal attitudes. Based on the evaluation results, this study posits that the development of urban low-carbon and smart initiatives should not be disjointed but rather synergistic and complementary. This study constructs an evaluation indicator system for the co-development of smart low-carbon cities aimed at better guiding the future coupling coordination development of smart and low-carbon cities.

The novelty of this study not only addresses the practical dilemma of obtaining comprehensive, accurate, and timely urban-level carbon emission data, a challenge due to existing measurement and estimation technologies being unable to capture all types of carbon emissions, but also assesses the urban SCP and LCL. Simultaneously, by combining qualitative and quantitative analysis methods, it fills the research gap on the nature of the coupled coordination relationship between urban SCP and LCL. Moreover, from the perspective of urban complex systems, this study dissects the urban low-carbon level into LCC, LC, LCE, LCEQ, and LCS, exploring their respective coupled coordination relationships with SCP. This clarifies the impact mechanism between SCP and LCL, providing a theoretical basis for smart low-carbon city co-development. The limitations of the study are also appreciated. Firstly, the study only selected a sample of cities in China, and the limited number of samples may not fully substantiate the research conclusions. Secondly, the indicator system constructed by this study is still not perfect, leading to certain inaccuracies in the evaluation results. In this regard, future studies are recommended to conduct a more comprehensive comparison analysis on the coupled coordination relationship between SCP and LCL at city, regional, and national levels, which would be beneficial in better guiding the practice of urban sustainability.

Data availability

All data generated or analysed during this study are included in this published article [and its Supplementary Information files].

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Zhu, X., Li, D., Zhou, S. et al. Evaluating coupling coordination between urban smart performance and low-carbon level in China’s pilot cities with mixed methods. Sci Rep 14, 20461 (2024). https://doi.org/10.1038/s41598-024-68417-4

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DOI: https://doi.org/10.1038/s41598-024-68417-4

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