Compared with carbon dioxide, methane has a shorter lifetime and higher global warming potential (GWP) and also acts as a key ingredient of ground-level ozone pollution, so it is of great significance to control its emissions regarding climate change and air pollution mitigation. However, methane emissions are still growing up, in which livestock and oil/gas system are key categories. Regarding emission by parties, it shows a downward trend in Annex I parties to the United Nations Framework Convention on Climate Change while non-Annex I parties face challenges. The major policies and measures (PaMs) implemented and adopted are regulatory ones (e.g. standards) to control methane emissions, supplemented by market-based measures. In the meantime, voluntary agreement and partnership are critical to find the most cost-effective options. China has achieved effectiveness in methane controlling by bunches of PaMs, as low growing rate of overall emission and even declining in some sectors is observed. Nevertheless, challenges are ahead, including high cost, emission growing induced by structural factors and weak supporting systems. Based on these findings, policy recommendations are raised.
The status, trends and key sources of CH4 emissions in Annex I countries are explored, based on GHGs emissions data from Parties submitted by Annex I countries to the United Nations Framework Convention on Climate Change (UNFCCC) from 1990 to the most recent inventory year (2020). The results show that: (1) In 2020, the total CH4 emissions of the 42 countries in Annex I of the UNFCCC were 1872231.01 kt CO2-eq, and the combined CH4 emissions of the United States, the Russian Federation and Australia accounted for 60% of the total emissions. (2) Compared with 1990, the overall CH4 emissions of Annex I countries/groups of UNFCCC showed a downward trend in 2020, of which United States, the Russian Federation, Australia, the European Union (Convention) and the European Union (Kyoto Protocol) decreased by 14.79%, 29.69%, 24.01%, 40.56% and 40.34% respectively, while Turkey, Spain, New Zealand and Ireland increased by 50.62%, 2.49%, 3.97% and 7.91% respectively. (3) CH4 emissions in major developed countries mainly come from the agricultural and energy sectors, followed by the waste sector. Among them, in the agricultural sector mainly from enteric fermentation, followed by manure management; CH4 emissions from the energy sector come mainly from escape emissions from fuels; The main source of emissions in the waste sector is solid waste landfills.
The coal sector, which is the largest anthropogenic methane source in China, accounts for 38% of the country’s total anthropogenic methane emissions. Studies have identified significant uncertainties in existing inventories, indicating the urgency to enhance the accuracy of China’s coal methane inventory. Using a self-built dynamic mine-level database and high-tier methodologies in emission calculation recommended by IPCC (Intergovernmental Panel on Climate Change) inventory guidelines, this work improved China’s coal methane inventory and revised the estimation of coal methane emissions in 2012 and 2014. The results show consistency of coal methane emissions in 2012 between this work (23.33 Tg) and China’s national greenhouse gas inventory (23.85 Tg). However, it is important to note that the consistency observed in 2012 does not guarantee the accuracy of China’s national inventory due to significant discrepancies among sub-sources. In fact, coal methane emissions in 2014 were found to be 25.87 Tg, or 23% higher, compared to the national inventory. Further analysis reveals that abandoned mine methane (AMM) is the most significant source of this discrepancy, which has emerged as the second largest contributor of coal methane emissions, accounting for a share of 10%?20%, but has been substantially underestimated in previous studies. Additionally, this work identifies the dynamic variation of key parameters, such as the emission factor, as having a significant impact on inventory accuracy. It highlights the importance of timely updates to fundamental data, such as the timely measurements of mine gas gushing rates. Overall, this work makes significant contribution to improving the accuracy of coal methane inventory, supporting policy decisions of methane mitigation, and ensuring high-quality compliance.
Based on the meteorological data of 119 national meteorological stations in Henan province in recent 55 years (1968-2022), the daily precipitation phase was labeled by daily weather phenomena, and the standardized snowfall fields were divided by the REOF (Rotated Empirical Orthogonal Function) method. A local regional snowfall identification method was established by using the double temperature threshold method fitted with the exponential equation. After obtaining more accurate snowfall amount through snowfall identification, the response of snowfall to temperature and precipitation under the background of climate change was quantified. The results show that the double temperature threshold method fitted with the exponential equation has a high accuracy in snowfall identification in Henan province. The exponential equation can estimate the annual snowfall well. The correlation coefficient in each region is more than 0.97, and the absolute value of the average relative error is less than 2.7%. The increase of temperature contributed positively to the decrease of snowfall, and the effect intensity gradually weakened from south to north, and the decrease of precipitation contributed positively to the decrease of snowfall. Under the background of climate warming, the significant increase of temperature after 1994 played a major role in the influence of snowfall, and the probability of low temperature precipitation decreases, resulting in the overall decreasing trend of snowfall in Henan province.
Urbanization under local climate change often has a significant impact on the occurrence and development of heavy precipitation. In order to explore the role of urbanization and thermal environment on heavy precipitation in Kunming, the hourly precipitation data of Kunming station in the urban area and Jinning station in the suburban area during the wet season (May to October) from 1991 to 2021 were used for analysis. On the basis of revealing the difference and change trend of heavy precipitation at urban and suburban stations in different urbanization stages, combined with MODIS land surface temperature remote sensing image data, further exploration was made on the spatio-temporal distribution of urban thermal environment and its quantitative relationship with urban heavy precipitation in the daytime and nighttime during the wet season in the main urban area of Kunming. The results are as below. In the past 31 years, the heavy precipitation amount (HPA) and heavy precipitation frequency (HPF) at urban and suburban stations have shown an upward trend. Among them, the overall growth rate of HPA and HPF in urban areas is greater than that in suburbs, with significant differences between urban and suburban areas. The contribution rates of urbanization to HPA and HPF in urban areas reach 47% and 40%, respectively. Since the beginning of the 21st century, the total precipitation in Kunming urban area has decreased, and the contribution rate of HPA and HPF in the urban area has been continuously increasing, with their linear trends showing higher significance during the rapid urbanization stage. The heavy precipitation in Kunming urban area is mainly active from 19:00 to 05:00, belonging to a single peak pattern with a nighttime activity. The peak of heavy precipitation occurs at 04:00, and the “night rain” characteristic is significant. HPF has the main contribution to HPA. During the period from 1991 to 2021, there was no significant trend in heavy precipitation at urban and suburban stations during the daytime, while the contribution rate of heavy precipitation and frequency at night at urban station showed an upward trend, which was significant in the rapid urbanization stage of the past 17 years. From 2005 to 2021, the nighttime urban thermal environment index significantly increased compared to the daytime, indicating a significant urban thermal effect. Through correlation analysis, it is found that the urban thermal environment has a positive promoting effect on heavy precipitation in urban areas, and the high significance of this effect is mainly manifested at night.
Rainstorm disaster is a common kind of disaster that threatens the safety of urban life and property, and the historical relics exposed therein are faced with the great inundation risk. Scientifically predicting the inundation risk of historical relics and carrying out rescue work in time can effectively improve the rescue efficiency. Taking 154 historical relics in Henan province as the research object, based on SCS-CN model and GIS spatial analysis technology, 65 catchment areas containing historical relics were extracted through hydrological analysis to study the risk of historical relic inundation under rainstorm scenarios. Firstly, the critical rainfall of historical relics submerged was calculated in each catchment area. Then, comparing with the actual rainfall scenarios during the “July 20 Henan Rainstorm” period, from 8:00 on July 20 to 6:00 on July 21, from July 20 0:00 to 21 24:00, and from July 18 0:00 to 21 24:00, the areas with inundation risk were identified respectively. Finally, the inundation risk of historical relics was systematically evaluated. The results show that: (1) Extreme rainfalls for many consecutive days can easily create widespread ponding in the catchment area, and as the duration of continuous rainfall increases, the threat of inundation of historic relics becomes more severe; (2) The catchment areas with low critical rainfall are more likely to be flooded when rainstorm comes, and the inundation risks of historical relics in these areas are relatively high; (3) Topographic conditions and development degree have become important factors affecting the inundation risk of historical relics under extreme rainfall scenarios, so that areas with high risk are mostly located in low-lying areas with high development degree; (4) The planning should focus on high-risk points and their corresponding catchment areas by implementing classified prevention and control, building a flood control and disaster relief system, and establishing a risk early warning mechanism to effectively improve the urban resilience. The research results are expected to provide useful reference for the emergency management of historical relics under the rainstorm disaster scenarios.
In the context of China’s carbon peaking and carbon neutrality target, it is important for building sector to establish a roadmap to achieve these targets. Many countries have already committed to carbon peaking and neutrality goals to tackle climate change. The global comparison of building energy use and carbon emissions is an essential tool to understand the current state, predict future developing trend and design a carbon neutrality pathway for building sector in China, which can also provide guidance for other developing countries to establish similar pathways. In this paper, a method for calculating and comparing building operation energy use in different countries is proposed. The method applies the electricity-equivalent method to calculate the total energy use of building operation, and uses energy conversion factor benchmark to decouple building energy use and energy conversion system. Additionally, a comparative method for building operational carbon emissions is presented. The method is applied to conduct a global comparison of building operation energy use and carbon emissions in various countries. Then, the dominant factors of carbon emissions and the main issue in achieving carbon neutrality are analyzed. The results indicate that building operation energy use per capita or per unit floor area and carbon emission intensity in China are still relatively low compared to developed countries. However, carbon emissions per capita and carbon emission per unit equivalent electricity consumption of building operation in China are both higher than the global average. Finally, policy recommendations are proposed for carbon neutrality pathway in China’s building sector. On the one hand, it is important to maintain a green and low-carbon lifestyle and keep building energy demand reasonable. On the other hand, it is suggested to promote the electrification of building energy use, as well as promoting the low-carbon transition of energy system to increase the proportion of renewable electricity generation.
The mechanism of utilizing carbon trading to promote deep agricultural emission reductions is a topic of urgent discussion. This article reviews the theoretical foundations of utilizing carbon trading to promote agricultural emission reductions, summarizes relative international practices, experience and obstacles, and provides insights into the pathway for utilizing carbon trading to promote agricultural emission reductions in China. Utilizing carbon trading to promote deep emission reductions in agriculture is theoretically and economically feasible when the transaction costs are lower than the cost savings. However, it faces various obstacles such as high emission uncertainty, lack of technical standards, unstable emission reduction effects, as well as high costs for monitoring, reporting, and verification in practice. The inclusion of agriculture in voluntary carbon markets has made significant progress in innovative organizational methods, constructing risk-sharing mechanisms, and developing accounting standards, while there is currently no successful practice of including agriculture in mandatory carbon markets. To accumulate experience and reduce transaction costs, agriculture should prioritize voluntary carbon markets and gradually transition towards mandatory carbon markets. Agricultural projects verified by Chinese Certified Emission Reduction (CCER) market are an important practice for agriculture to participate in voluntary carbon markets. Only when the policies, methodologies, and operational mechanisms are mature can we expand the quantity and scale of CCER agricultural projects. However, due to the crucial role of agriculture in food security and national economic development, the initiative of including agriculture in mandatory carbon markets must be discussed with utmost caution.
Through the column decomposition of China’s inter-provincial input-output table, this paper calculates the carbon emissions driven by provincial value added and import from the perspective of income-side, and analyzes the carbon emission reduction effects of provincial intermediate trade by using dual Structural Decomposition Analysis (SDA) and counterfactual scenario simulation. The results show that the inter-provincial trade driven by provincial added value and import implies large carbon emissions and carbon transfer during the study period. The carbon emissions cost per unit value added in Beijing-Tianjin region, the eastern coastal region and the southern coastal region are low, and these regions have higher carbon emission efficiency. Provincial value added significantly promotes the increase of provincial carbon emissions; The carbon emission coefficient changes from significant resistance effect to promotion effect; The scale of intermediate trade has promoted the increase of carbon emissions, and the structure of intra-provincial and inter-provincial intermediate trade has gradually shown significant resistance effect since 2012, which has become the main factors to drive provincial carbon emission reduction. From a new perspective of carbon emissions driven by value added, this paper provides a theoretical basis for reducing carbon emissions and achieving carbon neutrality through the adjustment of provincial intermediate trade structure.
The synergistic management of atmospheric pollutant and carbon emission can alleviate the dual pressure of improving environmental quality and reducing greenhouse gas emissions in China. It is crucial to clarify the synergy of carbon emissions trading, which is a key market-based instrument for carbon reduction. This paper examines the synergistic reduction effects of carbon emissions trading pilot policies on CO2, SO2, dust and PM2.5 using panel data of 30 provincial regions in China from 2006 to 2019 based on DID method, and explores the impact mechanism of the policies through mediating effects model. The results show that the policy has significant pollution and CO2 synergistic reduction effects, among which the synergistic effect of CO2 and SO2 is the most significant, but the long-term effects of the policy need to be enhanced. The mechanism analysis shows that carbon market can reduce CO2 and atmospheric pollutant by reducing energy consumption and adjusting energy structure, but the industrial structure does not have this transmission effect yet. In summary, this paper puts forward three suggestions: strengthen the supervision of carbon market and establish a sound long-term mechanism; insist on reducing energy consumption and optimizing energy structure; expand the range of industries covered by the national carbon market.
A core problem of global climate governance is how to reconcile the interest demands of various international actors with international/domestic objectives. Current studies on leadership in international climate negotiations usually start from the structural realism theory, most of which focus on the established or emerging powers, and emphasize the role of large countries and major greenhouse gas emitters in leading the international climate governance process, while paying less attention to the internal logic of small countries to strengthen leadership through institutional designing, knowledge shaping and discourse construction. The Alliance of Small Island States (AOSIS) firmly maintains the multilateral negotiating mechanism under the UNFCCC in its game with major country groups such as the EU, Umbrella Group, BASIC countries, Group of 77 and China. AOSIS promotes its own favorable agenda through diplomatic mediation and alliance strengthening, and constantly expands the moral right of discourse of Small Island States based on historical correction and moral concern. By leveraging the advantages of Small States in institution designing and knowledge shaping, AOSIS has achieved its unique “reverse leadership” in international climate negotiations.
