Significant changes of extreme cold events in China have occurred in the background of global warming. There are few studies focusing on the characteristics of extreme cold event change in the last century due to the limitation of observation data. By comparing the ETCCDI (Expert Team on Climate Change Detection and Indices) and the newly extended ET-SCI (Expert Team on Sector-specific Climate Indices) calculated from observations and two century-scale reanalysis datasets (NOAA-20CRv2 and ERA-20C), we analyzed the characteristics of the changes of extreme cold events in China. Consisting with global warming, the intensity, frequency, and duration of extreme cold events in China showed a decreasing trend since the early 20th century. Meanwhile, the number and duration of cold wave defined based on the ECF (Excess Cold Factor) presented the trend of reduction, and the decrease in Heating Degree Day (HDD) reflected the decreasing trend of heating energy demand in China. Trends of the characteristics of extreme cold event were more pronounced after 1951 in China, with trends of some indices significantly exceeding the century trends. The above showed that cold events had decreased rapidly since the mid-20th century. It’s worth noting that the two sets of centennial scale reanalysis data can be used to study the changes of regional extreme cold events in China, but the uncertainties are large in areas with insufficient spatio-temporal coverage of site observations, and the deficiencies caused by spatial coverage and quality issues need to be carefully considered.
Using the daily observational dataset of the surface air temperature in China from 1961 to 2020, and considering their probability density distribution and spatial extent, three kinds of temperature extremes were defined: the spatially consistent cold days, spatially consistent warm days, and extreme days with north-south dipole temperature in China during winter. The results show that a total of 960 days of the winter temperature extremes occurred in China. Among them, there are 358 consistent cold days, 271 consistent warm days, and 331 extreme days with north-south dipole temperature. Before the 21st century, the days and intensities of the consistent cold days showed decreasing and weakening trends respectively, and the cold days of winter and February decreased abruptly in the 1980s. Meanwhile, increasing and strengthening characteristics can be seen in consistent warm days, but only consistent warm days in December increased abruptly in the late 1970s. The decline (rise) of spatially consistent cold (warm) days during this period was most affected by changes of February. After entering the 21st century, it was the variations of the spatially consistent cold and warm days in January that led to the small increase of cold days and the increase of warm days in winter. Except for December, extreme days with north-south dipole temperature in winter and other months all showed abrupt decline in the 1970s and 1980s. Before the 2010s, the decline of the extreme days with north-south dipole temperature in winter was mainly influenced by the variation in February, after then, the variation in January played a dominant role.
Human activities have been thought as the key factors for the urban heat island effect. However, the impacts of anthropogenic factors on the intensity of the urban heat island effect at the city scale are still unclear. The intensity of daytime surface urban heat island (SUHI) at the city scale in China from 2012 to 2018 was calculated based on multi-source geographic data. Then the spatial and temporal patterns at the city scale were analyzed, following which the relationship between the driving factors and SUHI was discovered. Coupled with the shared socioeconomic pathways (SSPs) proposed by IPCC, the intensity of human activities under different scenarios were used to project the SUHI from 2020 to 2100. The spatial distribution of the annual mean SUHI at the city scale in 2012-2018 showed an obvious positive spatial autocorrelation. The southern China experienced higher SUHI than the northern China in general, and the strongest SUHI occurred in the southeast coast, with the weakest SUHI occurring in the northwest during 2012-2018. The mean value of SUHI slightly increased from 2012 to 2018 by 0.08℃ and was influenced by both anthropogenic and natural factors, among which GDP and ΔNDVI presented the largest contributions. From 2020 to 2100, the SUHI in most Chinese cities under the five SSPs scenarios will increase significantly, with the mean value of SUHI under the SSP5 scenario increasing by 0.67℃. In addition, the future SUHI in large cities varies largely under different scenarios. In terms of driving factors, the GDP will be the main anthropogenic driver of SUHI growth for most cities. Meanwhile, the comparative analysis for typical cities suggests that the fluctuations of SUHI in Shanghai urban agglomeration, Tianjin city, Urumqi and Nanning city may reach 4.83-8.98℃, 3.24-4.95℃, 1.11-1.55℃ and 2.61-4.05℃ at the end of the 21st century, respectively. The results of this study reveal the possible temporal and spatial changing trend of SUHI under the SSPs in future. The conclusions are important for achieving healthy development of urban ecological environment.
The quantitative evaluation system of urban climate carrying capacity, constructed by using climate natural influence factors and socio-economic development factors, was used to quantitatively evaluate the climate carrying capacity changes of Guangxi Beibu Gulf coastal city cluster (Beihai, Fangchenggang and Qinzhou) from 2000 to 2019. The results show that the climate natural capacity of the three cities increases with fluctuations during the study period, and the growth trend of Beihai and Fangchenggang is significant, reflecting the influence of urbanization on climate; the pressure of extreme climate events fluctuates sharply and the overall growth is not significant; the city climate pressure and city coordinated development ability of each city show an increasing trend in the process of urban development, but the growth of city coordinated development ability, is still insufficient to balance the negative impacts brought by natural climate factors and urban economic development. The overall climate carrying capacity of Beibu Gulf urban cluster shows a fluctuating and significant downward trend, reflecting the increasingly obvious constraints of the climate environment on the construction and development of coastal cities; the climate carrying capacity of three cities is sensitive to the changes of climate natural capacity and extreme climate event pressure indicators, and extreme low temperature, strong wind, persistent no rainfall and heavy rainfall events are the main threat factors to the stability of the climate system of the coastal urban agglomeration. In future development planning of the Beibu Gulf urban cluster, it is necessary to enhance the climate carrying capacity to improve the ability of science and technology to protect the environment, and defend against natural disasters, and taking the road of low energy consumption to cope with the pressure brought by climate change.
Based on the data of China’s provincial carbon emission and modernization index from 2000 to 2020, the spatial and temporal evolution characteristics of provincial carbon emission and modernization index were analyzed by traditional statistics and spatial autocorrelation analysis methods, and the influence of modernization level on carbon emission was detected by geographic detector method. The results show that the total carbon emission of 30 provinces in China has shown continuous growth in the past 20 years, while the total carbon emission growth rate has fluctuated down. It is worth noting that total carbon emissions showed negative growth in 2015. From the perspective of different regions, the total carbon emission showed a descending trend from east to west, and the carbon emission gap between east and central regions narrowed. From the perspective of spatial distribution characteristics of carbon emissions, high-value regions of China’s carbon emissions are mainly concentrated in the Bohai Rim region. With 2015 as the turning point, the changes of high-value regions of carbon emissions can be roughly divided into expansion stage and contraction stage. In the spatial correlation analysis, carbon emissions at the provincial scale in China have a significant spatial positive correlation, and the spatial concentration level of carbon emissions at the provincial level shows the characteristics of increasing first and then decreasing gradually. The number of regions with positive spatial correlation is more than that of regions with negative spatial correlation. Carbon emissions of most provinces in China are greatly affected by their neighboring provinces. Hebei is always in the high-high agglomeration area, and Shandong, Henan and Shanxi also show the characteristics of high-high agglomeration for many times. In the aspect of the modernization index research, the time change trend of modernization index is significant, and the spatial distribution evolution characteristics are distinct, which accords with China’s national conditions. From the perspective of influencing factors, transportation, average years of education, informatization level, absolute population size and industrialization level have strong explanatory power for carbon emissions. The combined effect of the two factors on carbon emissions is stronger than that of a single factor. The key interaction factors, including environmental regulation, absolute population size and industrialization level, have strong interaction effects on the spatial differentiation of provincial carbon emissions.
Based on a large number of literature and reports, this paper expounds on the connotation of non-energy use link, and summarizes and compares the core characteristics, construction concept, framework design principle, development process, application scope, advantages and disadvantages of different types of non-energy use and its corresponding GHG emissions accounting models caused by them. The results show that the IPCC-RA method can improve the accounting efficiency of non-energy use and its corresponding GHG emissions, and the IPCC-SA method can identify its source term distribution characteristics. The NEAT model can depict the impact of international trade structure on carbon flow in petrochemical products. The EPA-specific model is only for the United States. IPCC-RA can macroscopically control the evolution law of GHG emission corresponding to the energy consumption of raw materials in China and the distribution characteristics of the contribution of different fossil fuels to GHG emission from non-energy use. Therefore, based on IPCC-RA, the carbon emission and carbon storage of energy consumption for non-energy use purposed in China’s industrial sector were calculated. The results show that the energy consumption for non-energy use purposed from 2010 to 2020 was mainly petroleum, and the contribution of raw coal and naphtha to the carbon emission of energy consumption for non-energy use purposed was higher than that of other fossil fuels. The existing international models cannot effectively describe the effect of China’s unique petrochemical product trade structure on the carbon flow in the non-energy use link. It is suggested that in the follow-up study, the raw material energy consumption database of various process categories of different products at the enterprise level and the localized product-raw material matrix should be developed, and the localized fossil fuels consumption for non-energy use purposed and its corresponding GHG emissions accounting and prediction bottom-up model should be built.
The green development of civil aviation is the inherent requirement of promoting the high-quality development of China’s civil aviation, and is one of the important manifestations of improving the supply competitiveness of China’s civil aviation industry. China’s civil aviation market has huge demand potential. With the recovery of the market, energy consumption and carbon dioxide emissions will grow rigidly. Among the emission reduction technologies or measures concerned by the civil aviation industry, the use of Sustainable Aviation Fuel (SAF) has huge potential for emission reduction compared with the emission reduction measures such as aircraft and engine technology improvement, flight ground and air operation improvement and market mechanism, but the investment and cost are high. From the perspective of airlines, this paper constructs a model of emission reduction investment value using real option method, focuses on SAF investment strategies, including investment threshold, investment time, blending ratio, optimal investment conditions, etc., and analyzes the impact of market mechanism, fuel cost and other uncertain factors on the emission reduction investment behavior of airlines. It also puts forward the conditions for encouraging investment under carbon emission constraints and the mixing proportion to be used when airlines carry out emission reduction investment, which will provide some reference for the formulation of emission reduction strategies of airlines and relevant government policies.
Based on the established demand-emissions-cost model, combined with scenario analysis, this paper presents an assessment of the potential and cost of synergistic GHG mitigation in the room air conditioner sector in Hainan province. The results show that the room air conditioner sector in Hainan province can significantly reduce both direct and indirect emissions and achieve near-zero emissions by promoting energy efficiency improvements while converting HFCs refrigerants, as well as gain relative benefits through electricity saving. In the Kigali energy efficiency scenario and accelerated transformation energy efficiency scenario, the room air conditioner sector in Hainan province will achieve cumulative emission reductions of 50-62 Mt CO2-eq and 77-94 Mt CO2-eq from 2021 to 2060, with direct emission reductions accounting for about 30% and 55%, and average emission reduction costs of CNY -219.3 to -219.1/t and CNY -115.6 to -112.8/t, respectively.
In order to avoid double counting of emission reduction benefits, the market mechanisms established in Article 6 of the Paris Agreement, including the cooperation approaches referred to in Article 6.2 and the Article 6.4 mechanism, require corresponding adjustment of the emissions of participating Parties. The Glasgow Climate Change Conference adopted guidance for the implementation of the Article 6 mechanisms, including specific requirements for corresponding adjustment. For participating Parties that have a single-year Nationally Determined Contributions (NDC), the guidance provides two corresponding adjustment methods: the averaging approach and multi-year emissions trajectory approach. The averaging method is more concise and convenient in operation, allowing the Parties to achieve their NDC goal with a more flexible emissions path, while the multi-year emissions trajectory approach reduces the uncertainty in achieving NDC goal, and is less affected by the allowance banking and borrowing rules of emissions trading system (ETS). The analysis of China’s NDC target and possible future emission paths shows that the averaging method is more suitable for China. It is suggested that preparations should be carried out for China’s participation in the market mechanisms under Article 6 from the following aspects: quantifying NDC mitigation target, tracking NDC progress, and establishing a system for tracking and reporting Internationally Transferred Mitigation Outcomes (ITMOs) transactions.
The current global climate governance system is in a diversified pattern of “hybrid driving”, and the Climate Hybrid Institutional Complexes (C-HIC) came into being. The composition system in the C-HIC has informal hierarchy, heterogeneity and two-way compliance, which goes beyond the hierarchy, homogeneity and one-way compliance of the traditional system complex. This advantage makes its constituent systems based on the functional efficiency theory and governance power transfer theory in interaction, showing a higher substantive fit and political fit, which is conducive to promoting global climate governance towards good governance. In the face of the situation and development trend of the global climate governance system, China’s climate diplomacy in the new era should further comprehensively enhance its participation in the C-HIC, systematically enhance the coupling and coordination between its constituent systems, and creatively embed Chinese excellent traditional culture in the C-HIC to provide Chinese wisdom and Chinese contributions.
The number of people displaced by climate disasters is three times that by wars, with half of humanity already in the danger zone. As an effective adaptation measure and low hanging achievement in addressing climate change, the United Nations Early Warnings for All Executive Action Plan was released at the 27th Conference of the Parties to the United Nations Framework Convention on Climate Change. The plan will provide early warning to all people on Earth over the next five years (2023-2027) through the following four pillars: disaster risk knowledge and management, observation monitoring and forecasting, early warning communication and dissemination, and disaster preparedness and response capabilities, resisting increasingly extreme and dangerous weather. Early warning has significant social benefits in disaster prevention and reduction. Developing countries can avoid disaster losses that are ten times the cost of the system every year by spending hundreds of millions of dollars on early warning release systems. It is recommended to strengthen legal planning and streamline the various stages of early warning issuance, in order to improve the timeliness, accuracy, and authority of early warning issuance. It is to increase support for the Global Multi-hazard Alert System-Asia (GMAS-A), make GMAS-A a demonstration project of the United Nations Early Warning for All Executive Action Plan, and is give full play to the role of GMAS-A in disaster prevention and reduction in countries along the “the Belt and Road” and the world. At the same time, under the United Nations Framework Convention on Climate Change, the negotiation topic of “early warning services for developing countries” should be actively established, and China’s best practices and experiences should be exported to promote the construction of a community with a shared future for mankind.
