Decoupling Analysis of CO 2 Emissions in the Industrial Sector from Economic Growth in China

: China has become the largest CO 2 emission country since 2014. The industrial sector is the largest contributor to CO 2 emissions in China. This paper uncovers the spatiotemporal characteristics of the decoupling status of industrial CO 2 emissions from economic growth at the provincial level during 1995–2019 in China and analyzed the structural characteristics of the industrial CO 2 emissions. The results suggested that 2010 is an important turning point. Since 2010, the decoupling status of industrial CO 2 emissions from economic growth has kept a continuously improving trend. During 2016–2019, all provinces achieved decoupling of the industrial CO 2 emissions from economic growth. More than 20% achieved absolute strong decoupling. Four subindustries, including raw chemical materials and chemical products, production and supply of electric power and heat power, petroleum processing and coking products, and smelting and pressing of non-ferrous metals, with large CO 2 emissions’ contribution and a continuously increasing trend, should be paid more attention in the future CO 2 reduction policies formulation.


Introduction
During 1996-2019, the economy in China experienced rapid growth, with the GDP (gross domestic product) increasing at an average annual growth rate of 13.2%, much higher than the global average growth rate of 4.7%. However, rapid economic growth causes many problems, such as extensive energy consumption and emissions [1][2][3][4][5], serious environmental pollution [6], and health problems [3]. In 2018, China emitted 10 billion tons of CO 2 and accounted for approximately 28% of the global total emissions [7]. The industrial sector is the largest contributor (more than 60%) and has great potential in carbon abatement [4]. To achieve the CO 2 mitigation commitment in the Paris Agreement, uncovering the spatial-temporal and structural characteristics of the industrial CO 2 emissions in China is of great significance.
Many studies suggest that economic growth is an important driving factor of CO 2 emissions, especially in developing countries. For example, Chong et al. [8] proposed that economic growth (GDP per capita) contributed 50.5% (13.3 Mt), 56.5% (35.3 Mt), and 48.4% (63.7 Mt) of energy-related CO 2 emissions in Malaysia during 1987-1990, 1990-2002, and 2002-2014, respectively. Zhao et al. [9] indicated that with rapid economic development in China, energy consumption increased from 734.4 Mt to 2755.1 Mt during 1992-2012. This study also found that the industrial sector accounted for the largest proportion of all sectors in CO 2 emissions. Therefore, the industrial sector attracted much attention in the research Industry and Information Technology in China proposed the Industrial Green Development Plan (2016-2020). The Industrial Green Development Plan (2016)(2017)(2018)(2019)(2020) proposed that optimizing the structure of the industry and energy consumption is an important approach to promote energy saving in the industrial sector. Further investigating the structural characteristics of the CO 2 emissions in the industrial sector is necessary to provide scientific references to the structural optimization of the industrial sector. In terms of the industrial subsectors, the National Development and Reform Commission proposed the Modern Coal Chemical Industry Innovative Development Layout Plan in 2017, and Implementation Opinions on Ultra-Low Emissions in the Steel Industry in 2019. From a regional perspective, the Ministry of Industry and Information Technology put forward the Guidance Opinions on Strengthening Green Industrial Development of the Yangtze River Economic Belt in 2017. The national-level policies have provided macro direction for the carbon reduction of the whole nation. Identifying the provinces or cities where there are good local practices in both the economic development and the CO 2 reduction in the industrial sector is essential to further mitigate climate change and achieve carbon neutrality in the next step.
This study uncovers the spatiotemporal characteristics of the decoupling status of CO 2 emissions in the industrial sector from economic growth during the last two decades. It can help identify when and where there are good local CO 2 reduction practices and provide scientific references to propose more reasonable reduction policies, especially in the industrial sector. The structural characteristics of the CO 2 emissions in the industrial sector in China is investigated to identify which subsectors of the industrial sector have larger reduction potential. Paying more attention to the subsector with large CO 2 reduction potential in advance is more efficient when formulating the relevant policies and implement the reduction measures.

Decoupling Model
Mostly, economic growth is accompanied by energy consumption and carbon emissions. "Decoupling" means the break of the connection of "environmental badness" and "economic goodness" [17]. This research applies the Tapio's decoupling method to analyze the decoupling status of CO 2 emissions in the industrial sector from economic growth. The Tapio's decoupling model is as follows: where c i represents the CO 2 intensity in the industrial sector in year i, and the right side of the equation consists of two parts: CO 2i represents the CO 2 emissions in year i and GDP i represents the gross national product in year i. Within a given time, the relationship between CO 2 emissions and GDP can be given by the following equation: where e i represents the elasticity of ∆CO 2 and ∆GDP. ∆CO 2 represents the change of the industrial CO 2 emissions, and ∆GDP represents the change of GDP. There are two main types of decoupling classifications currently used. Juknys [24] specified three decoupling types: primary decoupling, secondary decoupling, and doubled decoupling. Tapio [20] expanded the decoupling based on the original typology into absolute decoupling and relative decoupling. Based on the Tapio's decoupling typology, this paper refers to the decoupling typology including 12 categories Loo and Banister [25] proposed. The detailed decoupling typology is shown in Table 1.

The CO 2 Emissions Evaluation
According to the IPCC (Intergovernmental Panel on Climate Change) Guidelines for National Greenhouse Gas Inventories [26], we applied the "up-down" method to evaluate CO 2 emissions caused by fossil fuel combustion. The emissions model includes CO 2 emissions caused by fossil fuel combustion and indirect electricity consumption. The calculation equation is as follows: where EC ij represents the industrial CO 2 emissions from province j in year i; E n represents the emission factor of the type n fossil fuel; F nij represents the type n fossil fuel consumption in year i in province j; e uj represents the CO 2 conversion factor of electric power in province j; and U ij represents the electric power consumption from province j in year i. The types of fossil fuel included coke, crude oil, gasoline, kerosene, diesel, fuel oil, liquefied petroleum gas, and natural gas. The calorific value and CO 2 emission factor of each type of fossil fuel are shown in Table 2. The parameters are all collected from the China Energy Statistical Yearbook. The factor of electric power-translated CO 2 referred to China's power grid unit power, which supplied the average emission factor.   Table 3. Since Chongqing was established as a provincial-level municipality in 1997, all analysis of Chongqing is during 1997-2019.

Industrial CO 2 Emissions
The CO 2 emissions in the industrial sector in China from 1995 to 2019 are shown in Figure 1. It mainly shows an increasing trend. The industrial CO 2 emissions in China increases from 2589.5 Mt to 7107.97 Mt, with an average annual growth rate of 4.6%.

Industrial CO2 Emissions
The CO2 emissions in the industrial sector in China from 1995 to 2019 are shown in Figure 1. It mainly shows an increasing trend. The industrial CO2 emissions in China increases from 2589.5 Mt to 7107.97 Mt, with an average annual growth rate of 4.6%.

Structual Characteristics of National Industrial CO 2 Emissions
According to Figure 3 for 22.5% of the total industrial CO 2 emissions during the study period. The smelting and pressing of the ferrous metals sector is an industrial subsector with large CO 2 emissions.
Since the contributions of the top six CO 2 emissions subsectors are above 5%, the temporal variation characteristics of the CO 2 emissions of these six subsectors in the past 25 years are shown in Figure 5. During 1995-2019, the CO 2 emissions of the six industrial subsectors mainly showed an increasing trend. In addition, the CO 2 emissions of the smelting and pressing of ferrous metals and the non-metal mineral products fluctuated at a stable level or even showed a slowly decreasing trend after 2010. During 1995-2010, the period of "9th Five-year Plan", "10th Five-year Plan", and "11th Five-year Plan" in China, China paid more attention to economic growth rather than environmental protection. After 2010, the central government of China put forward a series of macroscopic energy saving, carbon reduction, and climate change mitigation-related policies. The Industrial Actions Plan for Addressing Climate Change (2012-2020) is one of the most important influencing policies during this period. In this document, the governor concentrated more on the ferrous metal, petroleum processing, chemical products, construction materials, textile, and electronic equipment-related sectors. This is the main reason why the slowly decreasing trend of the CO 2 emissions in the two subsectors, smelting and pressing of ferrous metals and non-metal mineral products, appeared during the recent past decade.  Figure 4, the CO2 emissions of smelting and pressing of ferrous metals subsector contributed most, accounting for 22.5% of the total industrial CO2 emissions during the study period. The smelting and pressing of the ferrous metals sector is an industrial subsector with large CO2 emissions.

PEER REVIEW 9 of 15
Since the contributions of the top six CO2 emissions subsectors are above 5%, the temporal variation characteristics of the CO2 emissions of these six subsectors in the past 25 years are shown in Figure 5. During 1995-2019, the CO2 emissions of the six industrial subsectors mainly showed an increasing trend. In addition, the CO2 emissions of the smelting and pressing of ferrous metals and the non-metal mineral products fluctuated at a stable level or even showed a slowly decreasing trend after 2010. During 1995-2010, the period of "9th Five-year Plan", "10th Five-year Plan", and "11th Five-year Plan" in China, China paid more attention to economic growth rather than environmental protection. After 2010, the central government of China put forward a series of macroscopic energy saving, carbon reduction, and climate change mitigation-related policies. The Industrial Actions Plan for Addressing Climate Change (2012-2020) is one of the most important influencing policies during this period. In this document, the governor concentrated more on the ferrous metal, petroleum processing, chemical products, construction materials, textile, and electronic equipment-related sectors. This is the main reason why the slowly decreasing trend of the CO2 emissions in the two subsectors, smelting and pressing of ferrous metals and non-metal mineral products, appeared during the recent past decade.

Industrial CO2 Emissions and Economic Decoupling Analysis
Based on the periodical variation characteristics of the industrial CO2 emissions illustrated above, the period 1995-2019 is divided into five phases according to the period of China's Five-year Plan. The five phases are as follows: first phase (1995-2000), second   Figure 6 describes the spatiotemporal variation characteristics of the CO 2 emissions intensity in the industrial sector at the provincial level during 1995-2019. The industrial CO 2 emissions intensity showed a decreasing variation trend, and "low-east high-west" "low-south high-north" combined spatial pattern. Figure 7 and Table 4 illustrate the decoupling status of the CO 2 emissions from economic growth at the provincial level at the 5 phases covering 1995-2019. In the first phase (1995)(1996)(1997)(1998)(1999)(2000), more than 90% of provincial administrative units achieved decoupling status. Only Hainan and Chongqing did not achieve decoupling. The relationship between industrial CO 2 emissions and economic growth during 1995-2000 in Hainan and Chongqing was relatively strong coupling status. There were 13 provincial administrative units, more than 40%, achieving the absolute decoupling status. In addition, the decoupling status of four provincial administrative units, including Jilin, Hunan, Shaanxi, and Ningxia, were absolute strong decoupling, which is the most desirable decoupling status of CO 2 emissions from economic growth.      Table 4 illustrate the decoupling status of the CO2 emissions from economic growth at the provincial level at the 5 phases covering 1995-2019. In the first phase (1995)(1996)(1997)(1998)(1999)(2000), more than 90% of provincial administrative units achieved decoupling status. Only Hainan and Chongqing did not achieve decoupling. The relationship between industrial CO2 emissions and economic growth during 1995-2000 in Hainan and Chongqing was relatively strong coupling status. There were 13 provincial administrative units, more than 40%, achieving the absolute decoupling status. In addition, the decoupling status of four provincial administrative units, including Jilin, Hunan, Shaanxi, and Ningxia, were absolute strong decoupling, which is the most desirable decoupling status of CO2 emissions from economic growth.  In the second phase (2001)(2002)(2003)(2004)(2005), about 50% of provincial administrative units achieved the decoupling status. Only Anhui achieved the absolute decoupling of the industrial CO2 emissions from economic growth. However, the absolute decoupling status Anhui achieved is weak. The decoupling status of 13 provincial administrative units, including Hebei, Jilin, Jiangsu, Fujian, Jiangxi, Shandong, Henan, Hunan, Sichuan, Guizhou, Yunnan, Ningxia, and Xinjiang, changed from decoupling during 1995-2000 to coupling during 2001-2005. Generally, the decoupling status of the industrial CO2 emissions from economic growth became worse in the second phase.

Industrial CO 2 Emissions and Economic Decoupling Analysis
In the third phase (2006-2010), more than 90% of provincial administrative units achieved decoupling of the industrial CO2 emissions from economic growth. The decoupling status became better during the third phase compared with the second phase. However, the decoupling status achieved during the third phase were mostly the relative decoupling status. Only three provincial administrative units achieved absolute decoupling of CO2 emissions in the industrial sector from economic growth. The decoupling of industrial CO2 emissions from economic growth in Beijing and Zhejiang was absolute weak decoupling. The decoupling status Shanghai achieved was absolute strong decoupling. In 2003, Shanghai proposed an important policy to construct Yangpu Innovation Region and transform the "Industrial Yangpu" to "Knowledgeable Yangpu". The industrial structure shifted to modern design and intelligent manufacturing. The high-tech low-carbon industrial structure shift to local practice in Shanghai is worthy of reference for the developed regions, especially the provinces in the coastal eastern region.
In the fourth phase (2011-2015), the decoupling status of industrial CO2 emissions from economic growth improved further on the basis of the third phase. More than 90% of provincial administrative units achieved decoupling status. In particular, the absolute decoupling proportion increased from below 10% during 2006-2010 to nearly 50% in the In the third phase (2006-2010), more than 90% of provincial administrative units achieved decoupling of the industrial CO 2 emissions from economic growth. The decoupling status became better during the third phase compared with the second phase. However, the decoupling status achieved during the third phase were mostly the relative decoupling status. Only three provincial administrative units achieved absolute decoupling of CO 2 emissions in the industrial sector from economic growth. The decoupling of industrial CO 2 emissions from economic growth in Beijing and Zhejiang was absolute weak decoupling. The decoupling status Shanghai achieved was absolute strong decoupling. In 2003, Shanghai proposed an important policy to construct Yangpu Innovation Region and transform the "Industrial Yangpu" to "Knowledgeable Yangpu". The industrial structure shifted to modern design and intelligent manufacturing. The high-tech low-carbon industrial structure shift to local practice in Shanghai is worthy of reference for the developed regions, especially the provinces in the coastal eastern region.
In the fourth phase (2011-2015), the decoupling status of industrial CO 2 emissions from economic growth improved further on the basis of the third phase. More than 90% of provincial administrative units achieved decoupling status. In particular, the absolute decoupling proportion increased from below 10% during 2006-2010 to nearly 50% in the fourth phase. Fourteen provincial administrative units, including Beijing, Hebei, Liaoning, Jilin, Shanghai, Jiangsu, Shandong, Henan, Hubei, Hunan, Guangdong, Chongqing, Guizhou, and Yunnan, achieved absolute decoupling of the industrial CO 2 emissions from economic growth. The reason for the decoupling status improvement is mainly attributed to the macroscopic climate change mitigation policies.
In the fifth phase (2016-2019), all the 31 provincial administrative units in this research achieved decoupling of the CO 2 emissions in the industrial sector from economic growth. More than 70% of provincial administrative units achieved absolute decoupling status, and more than 20% achieved absolute strong decoupling of the industrial CO 2 emissions