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China plans to achieve the carbon peaking target by 2030 and will maybe implement a series of environmental regulation policies, primarily including energy supply policy (such as coal consumption constraint and non-fossil energy development) and carbon tax policy. This paper simulates these policies using a computable general equilibrium model. The simulation results indicate that carbon tax policy has a finite impact on the economy, the emissions reduction effect is also limited and carbon tax policy alone is insufficient to achieve China's 2030 carbon peaking target. The coal consumption constraint policy has a good emissions reduction effect, but is not conducive to economic growth. The non-fossil energy development policy can increase energy supply and promote economic growth, but the emissions reduction effect is inadequate. In general, the simultaneous implementation of the coal consumption constraint and non-fossil energy development policies could not only achieve the carbon peaking goal, but also narrow the energy gap and reduce pressure on economic growth. However, it is notable that if carbon tax policy and energy supply policy are implemented simultaneously, the emissions reduction effect of carbon tax policy would be significantly reduced; therefore, it is likely that no carbon tax will be levied in China.

Globally, the power sector must undergo a profound transition to achieve the decarbonization development targets. Various roadmaps are implemented, but only from a macro perspective, lacking the consideration of the electricity market rules. In this paper, we develop and present a market-driven generation and transmission expansion planning (MGTEP) model considering the effectiveness of the electricity market. Specifically, generation and transmission companies incorporate hourly market trading and annual capacity investment into strategic decisions to maximize their profits, with the supply function equilibrium model to analyze bidding behaviors. An equivalent quadratic programming formulation is deployed to solve the trilevel MGTEP model. Meanwhile, the MGTEP model is coupled with decarbonization policies to support the state and federal government in assessing energy transition strategies. We implement the MGTEP model with carbon emission allowance and carbon tax policies for the southern China electricity market to achieve carbon peaking by 2030. Carbon emission allowance adopts an intensity-based cap based on generation companies' historical output. The case study results show that 50 % carbon emission allowance or 400 CNY/t carbon tax is required but with several drawbacks, including unsatisfactory decarbonization effect, excessive economic sacrifice, etc. Finally, the case study is extended to dual-track policies with different combinations of policies. An optimal combination is 70 % carbon emission allowance and 160 CNY/t carbon tax. In this case, the power sector's carbon dioxide emissions and electricity prices in the southern China electricity market would increase to 554.6 Mt and 864.34 CNY/MWh in 2030, respectively, along with a carbon price of 850 CNY/t.

China's ‘dual carbon’ strategy is of strategic importance in leading global climate governance and promoting China's high-quality and green economic development. Cities are the centres of human activities. However, these are also places where high energy consumption and high carbon emissions are concentrated. This study selected data from 192 small and medium-sized cities in mainland China for the period 2000–2020. It classified these into seven categories using the K-means clustering method, calculated the decoupling status of different types of small and medium-sized cities based on the Tapio decoupling index, and analysed the relationship between carbon emissions and economic growth in various types of small and medium-sized cities based on the EKC curve theory. Finally, the backpropagation neural network (BPNN) model was used to classify and predict the time required to achieve carbon peaking for seven types of small and medium-sized cities. The following conclusions were drawn: (1) The development status of small and medium-sized cities shows a ‘geese echelon pattern’. New dynamic small and medium-sized urban areas may reach peak carbon emissions first, while resource-based small and medium-sized urban areas may be the last to do so. (2) The decoupling of carbon emissions from industrial development in small and medium-sized cities has not been completed. This manifests mainly through the states of declining decoupling, absolute decoupling, and strong negative decoupling. (3) A significant inverted U-shaped relationship exists between economic development and carbon emissions in these cities. (4) These cities may have the disadvantage of premature or excessive de-industrialisation. Additionally, these generally have an inefficient and expansionary economic development status. Therefore, this study contended for a more robust integration of a radical political economy and ecological economics to support the development of such cities in China. The paper proposes differentiated development paths and fundamental recommendations for small and medium-sized cities in the implementation of the ‘double carbon’ strategy. The intention is to provide theoretical guidance and implications for promoting green and low-carbon development in urban and rural areas and for the early achievement of the strategy in China.