Abstract: As the top carbon dioxide(CO₂) emitter, China has drawn global attention for its accelerated growth of CO₂ emissions in the past few decades, and international effort to stabilize the global climate depend greatly on the carbon emissions footprint of China. Recently, government officials, industry entrepreneurs and academic researchers have acknowledged that addressing climate change requires a balance between economic development and environmental sustainability. Moreover, this balance requirement has made the aggregate carbon emissions intensity(CEI), defined as CO₂ emissions per unit of gross domestic production, has been used to characterize the overall performance of climate change mitigation. In order to reduce CO₂ emissions, China promised to cut CEI by 60%~65% by 2030 compared with the 2005 level. Furthermore, the Chinese government aimed to peak CO₂ emissions no later than 2030 and increased the proportion of non-fossil fuels in primary energy consumption to 20% by 2030. In order to achieve these goals, we need to know what factors are driving the CEI change and their relative importance. Therefore, how to effectively decompose the driving factors of CEI in China has been an urgent problem.
In this study, a decomposition method of CEI is proposed, which is based on the production-theoretical decomposition method and index decomposition method. The CEI change can be decomposed into eleven driving factors in our approach, including energy mix change, potential economicoutput structure change, potential energy intensity change, potential carbon emission coefficient change, economic output gap change, technical efficiency and technological change ofeconomic output, technical efficiency and technological change of CO₂, technical efficiency and technological change of energy inputs. In addition, an efficiency measurement method that considers the materials balance principle is proposed to measure the technical efficiency of energy, economic output and CO₂, which can scientifically quantify the impact of technical factors on CEI.
Based on our proposed method, we decompose and analyze the driving factors affecting the CEI change of the transportation industry in China, with a panel data of 30 provinces during 2009~2017. The main results are as follows. From the national level, the CEI of the transportation industry declined by 18.65% from 2009 to 2017. Technological change of energy and CO₂ were the most critical driving factors decreasing CEI. In contrast, potential carbon emission coefficient change, energy technical efficiency change and CO₂ technical efficiency change led negative impacts to CEI decrease. At the provincial level, twenty-two provinces contributed positively to aggregate CEI. Shandong had the largest contribution to CEI decrease, while Anhui and Xinjiang were the top two for CEI increase. The specific suggestions are as follows: (1)The transportation sector needs to accelerate the optimization of the energy structure. They should focus on clean energy with low carbon content, gradually change the petroleum-dominated energy structure and form an energy structure with petroleum as the main body and joint development of multiple clean energy. (2)China has some rooms for improvements in reducing CEI by technical efficiency change. Transportation sector cannot just be limited to the investment of hardware technology but should pay more attention to the investment of management technology. They should rationally adjust the transportation structure, improve transportation management and dispatch, strengthen the technical training of traffic practitioners, and improve the operational level and transportation efficiency. (3)Technology progress is the essential measure to achieve CEI targets in the future. The Chinese government can formulate some policies to promote the development and application of advanced technologies in the transportation industry, gradually reduce the proportion of vehicles that use diesel and gasoline as the primary energy consumption. In addition, due to the different levels of technology in each region, the government can promote technological exchanges among regions and provinces to achieve diversified technologies.

Key words: carbon emissions intensity, production-theoretical decomposition, index decomposition, materials balance principle, transportation industry

摘要： 探索影响碳强度变化的因素对于制定科学的减排措施、实现减排目标具有重要意义。本文基于生产理论分解法和指数分解法提出了一种新的碳强度变化分解方法,该方法除了提供能源结构、经济产出结构等因素对碳强度的影响信息外,还提供了能源、经济产出、CO₂排放的技术因素对碳强度的影响信息。此外,本文构建了一种考虑物质守恒原则的效率测量方法,以测量能源、经济产出、CO₂排放的技术效率,从而科学量化技术因素对碳强度的影响。最后,本文使用2009年至2017年间中国交通运输行业的面板数据,从国家和省级层面来探究交通运输行业碳强度变化的影响因素。实证结果表明,能源技术进步和CO₂技术进步是降低碳强度的关键因素,而潜在的碳排放系数是阻碍碳强度降低的主要因素。

关键词: 碳强度, 生产理论分解法, 指数分解法, 物质守恒原则, 交通运输行业