To respond to global climate change, reducing carbon dioxide emissions is one of the vital goals of China's medium- to long-term development. Based on the extremum condition of function, this paper studies the theoretical conditions of carbon peak, and verifies the results based on examples of some main developed countries. It also analyzes present situation in China according to the above conditions, and finally forecasts China's carbon dioxide emissions during the process of carbon neutrality in 2060 after carbon emission peak in 2030 under baseline and enhanced scenarios. The results are shown as follows: (1) Based on an IPAT approach, carbon dioxide emission function is divided into three factors of population, per capita GDP and carbon intensity. The year of carbon peak emerges when the sum of the annual growth rates of the three factors changes from positive to negative. This conclusion has been verified by the historical data of selected main developed countries. (2) According to the historical data of China's population, per capita GDP and carbon intensity, the sum of the annual growth rates of the three factors has declined since 2003 and fluctuated between 0.01 and 0.02 in recent years, which indicates that there is a positive trend towards carbon emission peak generally. Moreover, according to the expected development goals of the three factors, the upper limit of China's carbon dioxide emission peak in 2030 is 11.22 billion tons. If the compound annual per capita GDP growth rate keeps unchanged from 2021 to 2035, the absolute value of compound annual growth rate of carbon intensity needs to be 0.14% higher than that of per capita GDP. (3) Given the premise condition that the total energy consumption decreases gradually, in 2060, the proportion of non-fossil energy is about 65% and the carbon dioxide emission is about 3.14 billion tons under the baseline scenario, while it is about 70% and 2.66 billion tons respectively under the enhanced scenario. However, carbon sequestration technologies such as carbon sink and CCUS are still uncertain, and the task of carbon neutrality is still arduous. To achieve carbon peak and carbon neutrality, it is crucial that energy consumption should be controlled and low-carbon consumption behavior should be advocated.

China puts forward the strategic goal of achieving carbon peaks by 2030 and carbon neutrality by 2060. Improving carbon emission efficiency and promoting green and low-carbon development are important ways to achieve the "dual carbon" goal. The study uses the Super-SBM model that includes undesired output to measure the carbon emission efficiency of 68 low carbon cities in China from 2003 to 2018 and analyzes their spatio-temporal evolution characteristics. The panel regression model is used to analyze the influencing factors of urban carbon emission efficiency. The following conclusions are drawn: (1) The carbon emission efficiency of low carbon city has shown an overall upward trend over time, from 0.169 to 0.423, with an average annual growth rate of 6.31%, and there is still room for improvement. (2) Regional differences in the carbon emission efficiency of low carbon cities show a trend of shrinking first and then gradually expanding, and a declining distribution pattern of "from eastern to central and western region" in space; the carbon emission efficiency of pilot city at various levels is characterized as "megacity > supercity > large city > medium-sized city > small city". (3) Economic development level, industrial structure, urbanization level, green technology innovation and carbon emission efficiency of a pilot city are significantly positively correlated, and the intensity of foreign investment has restrictions on urban carbon emission efficiency. There are some differences in the degree of influence of each factor on the three regions and cities of different sizes. The paper puts forward countermeasures and suggestions from the aspects of innovation input, industrial structure and regional differentiation, which has certain reference significance for promoting urban green and low-carbon development and the construction of ecological civilization.

Beijing-Tianjin-Hebei (BTH) is not only one of core economic regions of China, but also the key area of energy consumption and air pollution of the country. The carbon emissions of this region account for about 1/5 of the country's total. The proposal of China's "carbon peak and carbon neutrality" target has aroused widespread concern from the domestic and international community. Therefore, exploring the carbon emission trend and reduction potential of the BTH region under different scenarios is of great significance for China to achieve the carbon peak goal by 2030 on schedule. By analyzing the relationship between carbon emission and its influencing factors, this paper constructs a dynamic model of carbon emission system in the study region. On this basis, six scenarios are set up from the perspective of industrial structure, energy intensity, energy structure, environmental regulation, science and technology investment, and comprehensive regulation to predict the impact of different schemes on the peak time and peak value and reduction potential of carbon emissions in Beijing, Tianjin and Hebei respectively. The results show that under the baseline scenario, according to the existing system behavior law, Beijing has reached its carbon peak, Tianjin is expected to reach its carbon peak in 2023, and Hebei is unlikely to reach its carbon peak before 2035. In the coordinated development scenario, that is, the comprehensive regulation policy, compared with the single measure scenario, the effect of carbon emission reduction in each region is the best. Among them, the carbon emissions of Beijing from 2020 to 2030 will decrease by 13.52% on average compared with the baseline scenario. The carbon peak time of Tianjin can be advanced to 2021, and the carbon emissions of Hebei can reach the peak in 2030. Under the single measure scenario, the environmental protection scenario has the most significant effect on carbon emission reduction in Beijing, while the energy conservation and emission reduction scenario is the best development model to achieve the carbon emission peak in Tianjin and Hebei. Meanwhile, considering the differences in the peaks of carbon emissions in Beijing, Tianjin and Hebei, China should formulate differentiated carbon peaking strategy and emission reduction path.

China's carbon emission peak is an important agenda for global climate governance. The research on carbon emission peak in China by province has important influence and practical support for the national carbon mission peak and path arrangement. Based on the Hybrid-units Energy Input-Output model, this paper built a carbon emissions peak prediction model. Under 9 combined scenarios of economic development and carbon emission intensity improvement, the total carbon emissions of 30 provincial-level regions from 2020 to 2040 were predicted (except Tibet, Hong Kong, Macao and Taiwan). Then, this paper compared the peak values of different periods to estimate the carbon emission peak time. On this basis, the Probit model was used to analyze the influencing factors of whether regions can reach carbon emission peak before 2030. The results show that: (1) The carbon peak time varies significantly among provincial regions of China with a north-south strip aggregation in the spatial pattern. (2) The improvement of carbon emission intensity has a greater impact on the emission peak time, and the improvement rate of 4% per year is most favorable for reaching the peak by 2030. (3) Industrial structure, the degree of government intervention, and the degree of openness have a significant impact on whether the carbon peak target can be achieved by 2030.

Carbon neutrality is a common problem faced by all countries in the world. Against the background of economic globalization and trade liberalization, the total volume of international trade grows rapidly. With the deep international division of labor and industrial transfer, producers and consumers of trade objects have caused serious spatial displacement on the land surface. The bibliometric software CiteSpace is applied to analyze relevant literature on carbon neutrality under the theme of international trade and reveal the trend of "carbon neutrality" in international trade. The results show that: (1) The spatiotemporal evolution of greenhouse gases on a global scale has made trans-regional and multi-scale global carbon governance more complex. The developed countries have transferred high-pollution and low-value chain industries to the developing countries, and the principle of carbon accounting based on producer responsibility is no longer applicable to international trade cooperation. (2) Import and export trade is gradually becoming the driving force for the economic development of emerging economies. Global carbon governance should gradually move closer to the globalization of economic cooperation and regional integration. The global climate policy design should start from the fairness of the international carbon market, continuously optimize the carbon emission accounting system, improve the carbon accounting method, and analyze the expected effect of global carbon emission reduction through modeling. It is necessary to improve the awareness of the carbon emission reduction responsibility of industrial sectors, improve the utilization efficiency of industrial clean technology and energy, and to change the capacity of an ecological system to increase carbon sink and reduce emissions. While receiving technical assistance from the developed countries, emerging economies should focus on their energy industries, develop renewable energy industries, improve energy efficiency, and use economic policies and financial instruments to promote the development of their climate change investment and financing industries. Global carbon governance should pay more attention to equity, economic development, and environmental and resource differences among countries, and encourage more countries to participate in global or regional integration of carbon governance by using various carbon governance tools and ways of consultation and cooperation. The Chinese goverment must improve the carbon market mechanism, raise the level of carbon governance, and provide the "greatest common divisor" for international cooperation on carbon governance through domestic multi-industry and multi-sector emission reduction and international carbon emission reduction and carbon neutrality practices.