Apparent temperature (AP) describes the actual temperature felt by the human body. Based on meteorological data such as temperature, relative humidity, and wind speed from 1960 to 2019 in China, the spatiotemporal variation patterns and high temperature risks of AP were estimated and analyzed in four typical climate zones (humid zone, transitional zone, arid zone, and Qinghai-Tibet Plateau). The results showed that: (1) In terms of spatial distribution, AP decreased from the southeast coastal area to the northwest inland area, and the average AP value gradually decreased from the humid area (about 17.0℃) to the arid area (about 7.0℃) and the Qinghai-Tibet Plateau area (about 0.6℃). (2) The national AP showed a significant upward trend, with the rates in four typical climate zones being 0.29℃/(10 a), 0.27℃/(10 a), 0.15℃/(10 a), and 0.13℃/(10 a), respectively. (3) The contribution rate of temperature changes to AP was the highest, about 92.4%, followed by wind speed and relative humidity, about 5.6% and 2.0% respectively. (4) 70% to 80% of humid areas are defined as risk areas, and the number of days with high temperatures is increasing year by year. The 1.2% regional risk increase in the Qinghai Tibet Plateau is significant (0.22 d/a). Drought and transitional zones account for 30% to 40% of risk areas, and the risk gradually increases. The variation of high temperature risk days in typical climate zones showed spatial heterogeneity, with significant growth trends observed in most areas of humid regions and the Qinghai-Tibet Plateau.

Based on four dynamical downscaling simulations by the regional climate model RegCM4 (i.e., CdR, EdR, HdR, and MdR) and population projection dataset under SSP2-RCP4.5, the characteristics of the cluster high temperature events (CHTE) in China under 1.5℃ and 2℃ global warming were projected. The multi-model ensemble (MME) mean projection indicates the annual frequency increases by 31% and 44% respectively at the 1.5℃ and 2℃ warmer worlds compared with the reference period, and the extreme CHTE increases by 4.2 and 6.8 times respectively. Besides, the proportion of the CHTE indicators such as the cumulative intensity, duration, frequency falling into ‘large value range’ is expected to increase substantially. Compared with the CHTE under the 2℃ warming, a significant decrease of CHTE metrics across the country is projected at the 1.5℃ target, with remarkable regional differences. The reduction in frequency increases gradually from north to south. The duration decreases significantly by more than 6 days in Xinjiang and south of the Yangtze River (national averaged value is 0.2 days). The cumulative intensity decreases by more than 20℃ in the east-central China, and by more than 50℃ in the eastern part of Xinjiang (national averaged value is 0.6℃). In addition, under global warming of 1.5℃ and 2℃, MME projects that a widespread increase can be clearly found in the population affected by the CHTEs, with a significant decrease in the Inner Mongolia region and an increase in the central and eastern regions. The national population affected by the CHTEs increases by 1.4 times and 1.8 times, respectively. The urban population affected by the CHTEs increases more significantly (by 2.9 times and 3.8 times respectively), particularly with the most significant increase in the Beijing-Tianjin-Hebei region, Yangtze River Delta, Pearl River Delta, and Central China. The intensity exposure shows a significant increasing trend (by 2.2 and 5.2 times respectively) under the 1.5℃and 2℃ global warming, the same as the comprehensive exposure (by 1.2 and 1.8 times respectively). By contrast, the CHTE intensity exposure and comprehensive exposure on the urban population increase by up to 10 and 4 times respectively under the 2℃ global warming.

Under a warming climate, frost hazards have become increasingly more frequent in permafrost regions in North of Northeast China. In the studies of engineering design, construction and operation/maintenance in permafrost regions, research on the ground temperature fields of engineered foundations is key to analyzing and solving problems due to frost hazards. In this paper, the finite element method was used to investigate the impacts of refilling of clean gravels on the ground temperature fields of runway foundation soils, and to predict the temperature fields of the foundation soils under the runway over a 30-year period of runway operation. The results indicate that the gravel refilling of runway foundation soils can significantly increase the maximum-depth of seasonal frost-penetration (MSF). The horizontal thermal influence of the refilling on the MSF of the foundation would extend laterally to about 30 m at each side. Then, by comparing the changes in ground temperature fields of the foundation structures with different refilling depths (1.5 (top of the refill) to 3.5, 4.5, 5.5 and 6.5 (bottom) m), it is found that the rate of change in MSF would gradually decrease when the bottom of refilling depth reaches 4.5 m. Finally, by simulating the values of MSF under no-refilling and different filling depths for different climate warming rates over the next 100 years as indicated by the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC), it is found that by 2100, the MSF under the SSP2-4.5 scenario would be 1.63, 1.86, 1.84, 1.84 and 1.84 m, respectively. Therefore, when using the refilling of clean gravels to mitigate frost hazards of runway foundation soils, the refilling bottom depth should be no smaller than 4.5 m. At the same time, the well-managed construction and good maintenance of drainage and/or barrier facilities for surface and subsurface waters near the runway should be considered in cases of abnormally rainy and/or snowy summers and falls. This study is helpful to understand the influences of gravel refilling on the thermal state of permafrost foundation soils, and can provide an important scientific basis for solving the problems of frost heave and thaw settlement of runway foundation soils in permafrost areas.

Under the background of climate warming and humidity increase on the Qinghai-Tibet Plateau, atmospheric water vapor is increasing. The impact of atmospheric water vapor on land surface radiation will inevitably affect the energy distribution and thermal stability of permafrost. Based on the meteorological and hydrothermal data of the Beiluhe station located in the central Qinghai-Tibet Plateau, the effects of relative humidity at the height of 2 m and typical summer rainfall events on land surface albedo and radiation components were analyzed. The results are as below. Atmospheric water vapor can effectively weaken short-wave radiation, absorb long-wave radiation from the ground, increase downward long-wave radiation, and thus reduce surface albedo. The influence of atmospheric water vapor on land surface radiation has obvious seasonal characteristics. In summer, atmospheric water vapor has the most obvious weakening effect on solar short-wave radiation, and releases more downward long-wave radiation. In winter, the weakening effect of atmospheric water vapor on solar short-wave radiation is relatively weak, and less downward long-wave radiation is emitted. During the study period, for every 10% increase in the relative humidity of the atmospheric in the Beiluhe region in summer and winter, the daily average value of solar short-wave radiation will decrease by 54.9 and 9.8 W/m², respectively. At the same time, the daily average value of downward long-wave radiation will increase by 14.8 and 3.9 W/m², respectively. In autumn, the change in atmospheric water vapor has the most significant impact on the surface albedo. When the relative humidity in the atmosphere decreases by 10% in autumn, the surface albedo increases by 0.15. In contrast, the impact in spring is the smallest. When the relative humidity in the atmosphere increases by 10% in spring, the surface albedo only decreases by 0.01. Different typical rainfall events in summer lead to an increase in near-surface water vapor density and soil moisture content at shallow depths, which reduces surface albedo, and the reduction is positively correlated with rainfall intensity. The research results provide a reference for the analysis of surface energy balance in permafrost regions on the central Qinghai-Tibetan Plateau under the background of climate warming and wetting.

The refined evaluation of flexibility resources under different permeability of wind power and photovoltaics contribute to clarifying the key phased tasks of the new power system flexibility enhancement. Based on the multi-time scale time chronological operation simulation model, the cost composition of power system flexibility enhancement was refined, and the new energy consumption promotion effect and system operating cost difference of a single flexible resource were quantitatively evaluated at different stages of new power system construction. The results show that the flexible transformation of coal power and pumped storage are more prominent in terms of economy and new energy consumption, respectively under low permeability of wind power and photovoltaics, at the present stage. In the future, under high wind power and photovoltaic permeability, the flexible transformation of coal power gradually loses its cost advantage, and the regulating efficiency and economy of gas power are better reflected, electrochemical energy storage and pumped storage have the best benefit for improving new power system flexibility. Therefore, at the present stage, the focus of the power system flexibility enhancement is the flexible transformation of coal power and pumped storage deployment, to promote the large-scale deployment of energy storage while using the gas power as transitional resources.

Since industrialization, methane (CH₄) has caused a global mean surface temperature rise of about 0.5℃, and a reduction in CH₄ emissions is critical to achieving the Paris Agreement’s long-term temperature goal. According to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), the relative contribution of CH₄ to total effective radiative forcing (ERF) was 11% from 1960 to 2019, compared with the decrease in the relative contribution of CH₄ to total ERF from 1750 to 2019. It was related to the change in the growth rate of CH₄ concentration in the atmosphere since the 1970s. Projections show that global CH₄ emissions are expected to be reduced by up to 45% by 2050, which will benefit reducing peak warming levels and global surface ozone concentration and helping to improve air quality. The report also points out that there is still a large uncertainty in the source and sink of CH₄, and it is still challenging to accurately quantify the CH₄ flux and attribute its changes. With the release of the Methane Emission Control Action Plan in China, the academic community needs to strengthen the research on CH₄ source and sink estimations and make progress in the inversion algorithm for satellite monitoring of atmospheric CH₄ concentration, to provide data support for CH₄-related mitigation policies in China.

The carbon emission factors of regional and provincial power grids are an important basis for accounting of the indirect carbon emissions of enterprise electricity consumption, but official data have problems of discontinuous time and long lag. In this paper, the regional and provincial power grid carbon emission factors from 2005 to 2021 were calculated by using the method published by the National Development and Reform Commission, People’s Republic of China. By comparing official data, the accuracy of the calculation results was verified. In-depth research was conducted on the distribution characteristics, change trends, and differences of emission factors, and application scenario analyses were conducted on the two types of emission factors. The results indicate that the carbon emission factors in regional power grids are higher in the northeast and lower in the southwest, carbon emission factors in provincial power grids are higher in the east and lower in the central and west, with an overall downward trend from 2005 to 2021. However, the inequality in low-carbon development between regions has intensified. The different power generation structures and input power sources in different provinces lead to significant differences in emission factors between provincial power grids and regional power grids. The emission factors of provincial power grids in eastern and central provinces are significantly higher than those of regional power grids, while the emission factors of western provinces are the opposite. To improve the accuracy of carbon emissions accounting for industry enterprises, priority should be given to selecting provincial power grid emission factors; to evaluate the emission reduction effectiveness of enterprises in various industries within the same region, it is necessary to avoid unfair issues caused by power differences in different provinces and prioritize the selection of regional grid emission factors.

To analyze the economics of electrifying heavy-duty trucks (HDT) for container ports’ hinterland transportation, a model was developed to estimate the present value of their generalized total cost of ownership (GTCO). The model considered factors such as purchase tax incentives, subsidies, loans, and emission costs. Next, an indicator was constructed for the economic analysis of electrifying HDT. Then, two electrification plans, namely “buy chassis and battery” (Plan One) and “buy chassis but lease battery” (Plan Two) were analyzed. The results show that two plans are not economical under the case conditions of whether emission costs are considered or not, but considering emission costs can effectively mitigate the cost disadvantage of electrifying HDT. If emission costs are considered and all other factors remain constant, Plan Two will be economical if the battery rental is less than CNY 56100, or the electricity price is less than or equal to CNY 1.28/(kW·h), or the fuel price is greater than or equal to CNY 8.48/L, or the energy intensity of diesel HDT (dHDT) is greater than or equal to 0.40 L/km, or the energy intensity of electric HDT (eHDT) is less than or equal to 1.34 (kW·h)/km. Similarly, if Plan One is made economical, it should satisfy that the battery price is less than CNY 221100, or the electricity price is less than CNY 1.23/(kW·h), or the fuel price is greater than CNY 8.72/L, or the energy intensity of dHDT is greater than or equal to 0.41 L/km, or the energy intensity of eHDT is less than or equal to 1.28 (kW·h)/km. Exempting eHDT from the vehicle purchase tax does not guarantee that either plan is economical, but it can improve the economical indicators of both plans. Although increasing the unit emission cost or subsidy amount of eHDT can ensure that both plans are economical, the required increase ratio is high, which may increase the financial burden on HDT drivers or the government.

To ensure the timely achievement of the “dual carbon” goal, China’s government has accelerated the formulation and implementation of climate related policies. Since the climate policy uncertainty (CPU) has a significant impact on the social economy, an accurate measurement of CPU is of great significance. Based on keywords frequency of climate policy uncertainty from 13 newspapers in China from 2008 to 2023, text mining technique was adopted to construct the China CPU (CCPU) index, whose robustness and effectiveness were tested through time interval replacement and comparisons of domestic and international indices. The results show that China’s policies to address climate change can be divided into four stages: the initial stage, the development stage, the consolidation stage, and the deepening stage. CCPU can accurately reflect the development process of each stage. Compared with the US CPU, CCPU index can reflect not only major global climate policy events related to China, but also China’s unique climate policy changes and development characteristics. This index can provide reference and guidance to government in formulating climate policies, to businesses in adapting climate change, to financial institutions in managing climate risks, and to investors in improving investment efficiency in the future.

New energy enterprises are the main forces of green innovation, and subsidy is a common instrument to encourage innovation. However, the effect of the subsidy on the innovation performance of new energy enterprises has not been systematically explored. This paper innovatively divides the innovation performance of new energy enterprises into innovation intentions and innovation behaviors. Taking the new energy listed companies in Shanghai and Shenzhen stock markets as research subjects, this paper explores the effects of the subsidy on innovation intentions and behaviors, and the moderation effect of the subsidy on innovation intentions transformation, with threshold regression model and moderation model. The results show that subsidy has a significant promotion effect on innovation intentions, an “S-shaped” effect on innovation behaviors, and a positive moderation effect on the transformation of innovation intentions. Besides, the positive effects of subsidy on innovation are more pronounced among small-scale, low-liability, and high-profit enterprises. The findings contribute to formulating and assessing subsidy policies for new energy enterprises.