The carbon emissions of electricity in the Yangtze River Economic Belt increased by 353.96 million tons, 352.24 million tons, 50.22 million tons and 151.56 million tons, respectively, in 2000–2005, 2005–2010, 2010–2015 and 2015–2020. During the period from 2010–2015 the incremental carbon emissions of electricity decreased significantly, and the carbon emissions of electricity increased from 2015–2020. In the lower reaches, the increment of power carbon emissions decreased from 2005 to 2010, 2010 to 2015 and 2015 to 2020, but the increment of power carbon emissions was greater than that in the middle and upper reaches. Since the implementation of the strategy for the rise of central China in 2004, the increment of carbon emissions in the middle reaches increased slightly from 2005 to 2010. In the upper reaches, the increment of power carbon emissions showed a negative growth from 2010–2015 and a positive growth from 2015–2020.
4.2.2. Absolute Factor Analysis
From 2000–2005 the economic scale of the Yangtze River Economic Belt contributed 70.36 million tons of power carbon emissions (
Figure 14,
Figure 15,
Figure 16 and
Figure 17). The contribution of economic scale to carbon emissions increased continuously from 2000 to 2005, reaching 19.9 million tons from 2014–2015. From 2000 to 2005, the proportion of thermal power in the power production structure of the Yangtze River Economic Belt reached more than 70%. With the rapid development of various industries, the demand for electricity has increased, and the economic scale and power carbon emissions have maintained simultaneous growth. The cumulative contribution of economic scale from 2005–2010 was 142.24 million tons, and the economic scale continues to drive the increase in carbon emissions. Regional GDP growth from 2007–2008 was at its lowest level from 2005–2010, during which the contribution of economic scale was below 3% (
Table 6) for the first time, contributing 26.71 million tons. From 2010 to 2015, the cumulative contribution of economic scale to carbon emissions was 141.69 million tons, and the contribution of economic scale gradually decreased to 23.87 million tons from 2014–2015. The proportion of tertiary industry in GDP increased from 42.84% in 2010 to 48.25% in 2015. The secondary industry saw the original 48.52% fall to 44.01% in 2015, with deepening economic restructuring, and the service industry development accelerated significantly. In the upper, middle and lower reaches economic scale is also the main driving factor, with a cumulative contribution rate of more than 50%. The cumulative contribution of lower reaches economic scale to power carbon emissions is 261 million tons, which is much higher than the cumulative contribution of upper and middle reaches economic scale to carbon emissions of 106.16 million tons and 84.62 million tons. The cumulative contribution of upper and lower reaches economic scale showed an upward–downward–downward state in 2000–2005, 2005–2010, 2010–2015 and 2015–2020. In 2000–2005, 2005–2010, and 2010–2015, the cumulative contribution of economic scale in the middle reaches showed a gradual increase. Overall, the contribution intensity of economic scale to power carbon emissions has weakened, but it is still the main factor driving carbon emissions. The contradiction between economic development and carbon emission reduction still exists.
From 2000 to 2005, the cumulative contribution of energy consumption in the Yangtze River Economic Belt was 90.20 million tons, and the rapid expansion of thermal power led to an increase in power energy consumption. The cumulative contribution of energy consumption from 2005–2010 was 81.66 million tons. From 2007 to 2008 the total energy consumption decreased from 347.78 to 340.49 million tons of standard coal (
Figure 18), and the contribution of energy consumption was inhibited for the first time. In the 2010–2015 period, with the promulgation and implementation of energy-saving emission reduction policies and increase support for renewable energy generation, the scale of hydropower and other clean energy power generation has expanded, and thermal power has stopped expanding rapidly. From 2013–2015, the total energy consumption gradually decreased, and the contribution of energy consumption scale slowed down. The continuous growth of social electricity consumption from 2015–2020 meant that the scale of thermal power generation expanded, driving the consumption of energy. During this period, the cumulative contribution of energy consumption was 33.23 million tons. In the four periods, the cumulative contribution of lower reaches energy consumption scale gradually decreased. The cumulative contribution of upper and middle reaches energy consumption in 2005–2010, 2010–2015 and 2015–2020 shows a downward–upward state. Energy consumption is the main positive driving factor for the increase in carbon emissions in Yangtze River Economic Belt and its regions. The reduction in energy consumption directly affects the carbon emission reduction.
In 2000–2005, 2005–2010 and 2010–2015, the population scale of the Yangtze River Economic Belt increased by 8.86 million, 12.19 million and 2.01 million, respectively. The growth of the total population will lead to the expansion of the consumption scale of residents to a certain extent. Indirect promotion of enterprises will increase capacity supply and stimulate electricity demand, thus the cumulative contribution of population size in these three periods has gradually increased. As China’s coastal areas, the lower reaches have developed rapidly, with a strong population siphon ability. In 2000–2005, 2005–2010 and 2015–2020, the cumulative contribution of lower reaches population scale to power carbon emissions exceeds the cumulative contribution of population size in the Yangtze River Economic Belt. The population scale of the middle reaches in 2015–2020 was negative for power carbon emissions, due to the impact of the pandemic. The year-end population growth rate in the middle reaches was −1.02% from 2019 to 2020. The contribution to carbon emissions from electricity in 2019–2020 was −0.69 million tons, exceeding the sum of the positive driving contribution of population size in 2015–2019.
In 2000–2005 and 2005–2010, thermal power generation accounted for more than 65% of electricity output. Electricity output and carbon emissions growth kept pace. In 2005–2010 the cumulative contribution of electricity output reached 121.63 million tons. In 2010–2015, the pulling effect of output scale declined. In 2006 the renewable energy law promulgated and implemented the power production structure to clean energy generation transformation and development. In 2015 the proportion of thermal power generation was below 60% for the first time. From 2015–2020 the scale of clean energy generation continued to expand, but in order to maintain the safety of power supply and demand thermal power scale has also increased. The cumulative contribution of output scale in this period is basically the same as that in 2010–2015. In 2000–2005, 2005–2010 and 2010–2015, the cumulative carbon emissions of the upper, middle, and lower reaches output scale to the carbon emissions showed a rising–falling state. As one of the main driving factors of power carbon emissions, the optimization of electricity output structure can further reduce the contribution of output scale to carbon emissions.
4.2.3. Relative Factor Analysis
With the rapid economic development of the Yangtze River Economic Belt from 2000 to 2005, many new thermal power units were built to meet the demand for electricity. The cumulative contribution of carbon intensity from 2000 to 2005 was 19.31 million tons. In 2005–2010, 2010–2015 and 2015–2020, the emerging industries in the Yangtze River Economic Belt have further developed, and the economic value of unit power has increased. In addition, the implementation of programs such as Energy-saving Medium and Long-term Special Planning (2004) and Controlling Greenhouse Gas Emissions (2016). Increase the research and development and investment of thermal power emission reduction technology, thus the cumulative contribution of carbon intensity to carbon emissions in 2005–2010, 2010–2015 and 2015–2020 is negative. The cumulative contribution of upper, middle and lower reaches carbon intensity from 2000–2005 was positive. Among them, the upper reaches had the most cumulative contribution. The reason is that the proportion of thermal power to total power generation increased by 5.84% during 2000–2005. The lower reaches economy is large, and the economic level is high. The inhibitory effect of power carbon intensity on the cumulative contribution of carbon emissions is greater than that of the upper and middle. Due to the rapid development of hydropower in the upper reaches, the upper reaches carbon intensity had a greater inhibitory effect on power carbon emissions in 2010–2015 and 2015–2020 than in the middle reaches.
In 2007 China issued Energy Development Plan, and in 2010 introduced the
Strengthen the elimination of backward production capacity notice. The Yangtze River Economic Belt has increased its support for clean energy power generation. By 2015, the installed capacity of hydropower in the Yangtze River Economic Belt was 225.37 million kWh, 4.7 times higher than that in 2000. Clean energy power production has gradually become an important hub of the power system. In addition, the energy consumption per unit of thermal power output has decreased and the electricity efficiency of energy conversion has improved. Compared with 2000, the standard coal consumption of thermal power supply decreased from 381.87 (g standard coal/kWh) to 301.79 (g standard coal/kWh) in 2015 (
Figure 19). Furthermore, in 2000–2005, 2005–2010 and 2010–2015, the output carbon intensity inhibiting carbon emissions increased. The cumulative contribution of upper reaches output carbon intensity to carbon emissions in 2005–2010 and 2010–2015 was greater than that in the middle and lower reaches. This was due to the optimization of the power structure in the upper reaches of the Yangtze River, and the shift to non-fossil energy generation.
The change in energy consumption carbon intensity reflects the change in power energy consumption structure, the Yangtze River Economic Belt geographical conditions, and resource endowments and other reasons limit; in addition, the high cost of oil power generation, natural gas fuel and high cost of transmission and distribution links. Thus, during the study period, the consumption of electricity production oil decreased, while the consumption of natural gas increased slightly (
Figure 18). Coal consumption accounted for 96.98% and 95.02% of the total energy consumption in 2000 and 2020, respectively. At the present time, the thermal electricity production in the Yangtze River Economic Belt is still dominated by coal energy consumption. Therefore, energy consumption carbon intensity has a slight pulling effect on electricity carbon emissions. The cumulative contribution of carbon intensity of energy consumption in the upper and lower reaches of the Yangtze River Economic Belt in the three periods of 2005–2010, 2010–2015 and 2015–2020 was positively driven.
The cumulative contribution of population carbon intensity in the Yangtze River Economic Belt in 2000–2005 and 2005–2010 was 89.84 million tons and 86.20 million tons, respectively. The living standards of residents in the region have improved and the level of electrification has increased. The rising per capita electricity demand of residents indirectly leads to the expansion of thermal power to meet the power supply. The cumulative contribution of population carbon intensity decreased significantly from 2010 to 2015 and increased slightly from 2015 to 2020. The cumulative contribution of lower reaches population carbon intensity showed a decreasing trend in four periods. The cumulative carbon emission contribution of upper reaches population carbon intensity from 2010–2015 was negatively driven. The cumulative contribution of the middle reaches to population carbon intensity in 2010–2015 was the lowest in its four periods. To further realize the carbon emission reduction, it is necessary to raise residents’ awareness of energy-saving electricity and promote sustainable development among economy, environment and population.
Per capita GDP reflects the level of regional economic development. Objectively, the increase in per capita GDP in the early stage of economic development will promote power carbon emissions, while in the GDIM method, per capita GDP has a weak inhibitory effect on carbon emissions. Vaninsky points out that per capita GDP is correlated with several factors, which are affected by Equation (13). Therefore, the impact of per capita GDP changes on power carbon emissions is only partially attributed to it. The other part is included in the impact of other factors on the carbon emissions such as Equation (15), which may lead to the inhibition of per capita GDP. On the other hand, the two relative factors of per capita GDP and energy intensity are composed of three absolute variables: they are economic, energy consumption and population. Among them, the absolute variables of economic scale are the molecules and denominators of per capita GDP and energy intensity factors, respectively. The absolute factors economy in per capita GDP is distributed not only in the previous economic scale and carbon intensity, but also in per capita GDP and energy intensity. Therefore, in the per capita GDP, the population scale may have a higher degree of carbonization of carbon emissions and play a reverse role as a denominator, resulting in a weak inhibition of per capita GDP. The above reasons may also be the reason why the cumulative contribution of per capita GDP and energy intensity to power carbon emissions is relatively lower than other influencing factors.
During the study period, the power energy consumption of the Yangtze River Economic Belt supported the economic growth rate of 10.22% with an average annual growth rate of 6.16%. With the progress of power technology, power energy efficiency has been improved and power energy consumption caused by unit GDP has gradually declined. Therefore, in the three periods from 2000–2005, 2005–2010 and 2010–2015, the inhibition of energy intensity on carbon emissions increased. The cumulative contribution of energy intensity in the four periods of upper, middle and lower was negative. The upper, middle and lower reaches in 2000–2005, 2005–2010, 2010–2015 energy intensity cumulative negative driving effect of carbon emissions increased. In 2015–2020, the cumulative contribution of upper, middle and lower reaches energy intensity negative driving weakened.