The response of cryospheric hydrological processes to climate change, and its impacts has become a key issue in global change research. On a global scale, the mass loss of glaciers (i.e., the amount of meltwater from glaciers) has shown an accelerating trend over the past 20 years, ranging from (48±16) to (57.6±13) Gt/(10 a), while significant regional differences exist. At the watershed scale, the response of glacier meltwater to climate change varies among different watersheds, primarily depending on the size of the glaciers within each watershed and the compositional characteristics of glaciers of varying sizes. Although there are still differences in understanding the future trends of glacier meltwater across various glacier regions, particularly regarding the timing of critical inflection points, there is a consensus on the overall pattern of spatial changes in glacier meltwater. The future trend in global glacier meltwater is expected to be controlled by the rate of change in ice sheets and large glaciers at high latitudes. Global warming has led to significant changes in the intra-annual distribution of runoff during the snowmelt period, with a notable advance in the timing of snowmelt in most watersheds by up to 20 days. Additionally, early snowmelt runoff has significantly increased, with peak flow occurring earlier. It is projected that an increase in the rain-to-snow ratio in the future will lead to a reduction in snowpack storage, while simultaneously increasing sublimation, further advancing the timing of snowmelt runoff and reducing its contribution to watershed runoff. Climate change affects permafrost hydrological processes in several ways, including changes in the hydrological effects of the underlying surface, the runoff regulation function of the active layer, and variations in the supra-permafrost water. In terms of the hydrological effects of the underlying surface, enhanced freeze-thaw cycles, the expansion of thermokarst, and the deepening of the active layer directly impact surface runoff generation and flow processes, thereby affecting the intra-annual distribution of surface runoff. Regarding the runoff regulation function of the active layer, changes in the active layer not only influence surface runoff processes but also affect vertical and horizontal subsurface flow within the active layer, as well as the recharge and runoff generation capacity of the supra-permafrost water. The most important aspect is that the freeze-thaw dynamic and depth variation of the active layer play a role in regulating hydrological processes both within the year and over the long term. In terms of supra-permafrost water changes, various studies have shown that permafrost degradation has already impacted subsurface runoff to some extent, with the most significant effect being the direct contribution of permafrost degradation to river flow. In some watersheds, this contribution even reaches a substantial magnitude. The role of cryosphere hydrology at the watershed scale mainly manifests in three aspects: water source conservation, runoff replenishment, and hydrological regulation. Climate change has led to significant changes in the elements of the cryosphere, which in turn have altered the watershed functions of cryosphere hydrology. However, these changes vary greatly across different watersheds.

Climate change has led to rapid cryosphere changes in the Qinghai-Xizang Plateau, resulting in the increasing of the scale and frequency of cryosphere disasters. Consequently, cryosphere changes impose considerable threaten to the engineering safety, impacting the regional sustainable development and people’s well-being in the Qinghai-Xizang Plateau. This paper reviews the challenges faced by engineering in the cryosphere regions of Qinghai-Xizang Plateau, and expounds the cryosphere changes in recent years and its future change trends. From the perspective of the types of cryosphere disasters and the observed influence of cryosphere disasters on engineering, the influence of cryosphere disasters caused by cryosphere changes on engineering design and safe operation, as well as the economic cost of engineering construction and maintenance are discussed. The coping strategies to mitigate the cryosphere changes and disasters under climate change are put forward, and the coping strategies and technical measures of engineering are discussed.

The cryosphere human geography and environment is a discipline to study geographical distribution pattern and evolution law of human activities (population, livelihood, culture, economy, politics, etc.) in the cryosphere, which is closely related to cryosphere science, climate change science, environmental science, sociology and other disciplines. This discipline mainly focuses on human activities in the cryosphere region, how humans adapt to the cryosphere environment, and the comprehensive impact of these environmental changes on human society. The results show that: (1) During 1970-2024, the keyword of indigenous people have the highest frequency and the highest correlation with other keywords, followed by sustainable development, culture, climate change adaptation, community and health. These keywords have a prominent position and are the focuses and hot spots of the research on the human geographical environment of the cryosphere. (2) Keyword clustering forms the 10 most representative clusters of “climate change adaptation, politics, sustainable development, indigenous people, channel, health, food security, resources, culture and tourism”. (3) From 1990 to 2020, the population in the Arctic showed a slight decrease trend, while the population in the Qinghai-Tibetan Plateau showed an increase trend. Due to the restriction of the cryosphere environment, the inter-regional population migration was weak. (4) The cryosphere culture is dominated by the traditional culture of sea hunting, hunting and nomadism; the religion is dominated by primitive polytheism; the ethnic and linguistic diversity; and it is significantly affected by modern lifestyle and climate change. (5) The Arctic cryosphere is dominated by traditional reindeer industry and fishing activities, while the exploitation of mineral, oil and gas resources is mainly operated by enterprises. At the same time, the loss of Arctic sea ice has boosted the import and export trade of Arctic countries. The regional economic structure of the Qinghai-Tibetan Plateau cryosphere is dominated by animal husbandry. (6) Opportunities and risks coexist in cryosphere tourism. As a result of climate warming, its tourism comfort is increasing, the accessibility of tourism around the Arctic is increasing, and the impact on snow and ice resources in middle and low latitudes is significant, which has affected the sustainability of ski tourism. (7) Accelerated melting of polar ice caps and sea ice has enhanced the availability of polar resources. As the interests of many countries are involved, all countries intend to expand their territory or sphere of influence and obtain more resources, which leads to the strengthening of the game between major powers. The geopolitical problems of the middle and low latitudes cryosphere mainly focus on “water conflict”. In view of the significant impact of climate change on the human and geographical environment of the cryosphere, more attention should be paid to three issues in the future: the improvement of the livelihood and welfare level of the indigenous peoples in the cryosphere, the autonomy of the indigenous people in the cryosphere, and the sustainable development goals and realization paths of the polar regions.

This paper systematically reviews major extreme weather and climate events in China’s regions under the intensified global warming background from 2010 to 2023. It focuses on analyzing the characteristics and socio-economic impacts of these events and further summarizes the latest progress in attribution research on these occurrences. Among the annual top ten significant weather and climate events in China from 2010 to 2023, extreme precipitation and flood events, along with typhoons, accounted for the highest proportion at 27% and 15%, respectively. Extreme heat, drought, cold-related low-temperature and snowfall events, as well as pollution events associated with haze and dust, each accounted for 11%-12%, while severe convective weather and other meteorological events accounted for 7% and 6%, respectively. With the intensification of global warming, the frequency and intensity of extreme heat, extreme precipitation, and drought events in China have significantly increased. Trend attribution of extreme events focuses on the impact of climate change on their long-term trends. The increase in extreme heat and drought events is mainly attributed to anthropogenic forcing, while extreme precipitation, drought, wildfires, and other extreme events are also closely linked to human-induced warming. Human activities, particularly greenhouse gas emissions, are the primary drivers of the long-term changes in extreme events in China. Event attribution research focuses on changes in the probability and intensity of extreme events themselves. Studies based on circulation analog methods, atmospheric models, and storyline approaches indicate that human activities have significantly increased the intensity and frequency of extreme heat, drought, wildfire events, and compound hot-dry events, while slightly reducing the probability and intensity of cold events. The impact on precipitation events varies by event type, but most studies suggest that human activities have heightened the risk of extreme precipitation events. Despite significant progress in the attribution of extreme events in recent years, research gaps remain in understanding events like severe typhoons, severe convective weather, and other types of compound extreme events. Additionally, challenges persist due to insufficient observational data and the lag in climate model development. Establishing a real-time detection and attribution system will provide scientific guidance for the formulation and implementation of disaster prevention and mitigation policies, holding great significance.

Severe air pollution events by fine particulate matter (PM_2.5) and ozone (O₃) are the target of air pollution control in China. This paper reviews the research progress on the impacts of climate change on severe pollution events of PM_2.5 and O₃ in China in recent years. The results show that severe PM_2.5 pollution mainly occurs under stagnant weather conditions, while severe O₃ pollution mainly occurs under conditions of high temperature and low humidity. Climate change (including both anthropogenic global warming and the natural variability in the climate system) affects the local meteorological conditions that are conducive to severe pollution through changing large-scale circulation and regional circulation pattern. At present, the research on the impacts of climate change on severe PM_2.5 pollution is quite advanced, with the capability of identifying the impacts of climate factors or global warming on typical severe pollution events or the long-term trends of such events. However, there are few studies on the impacts of climate change on severe ozone pollution.

There are usually two kinds of metrics being used to measure emissions, including Global Warming Potential (GWP) and Global Temperature Change Potential (GTP). These metrics are scientific basis for making emission policies and thus have important reference for policy makers in manufacturing and related economic fields. Meanwhile, it is significant to quantitatively understand the effects of emission and its reduction on the past and future climate change. How to accurately calculate and reasonably apply GWP and GTP to assess the impact of emission on global warming is an important scientific issue and a hot topic in climate change. Therefore, it has received extensive attention from the scientific community and related fields. IPCC AR5 and AR6 have set up special chapters for GWP and GTP to summarize and discuss the content of calculation methods and their application development. Based on the discussion of GWP and GTP in IPCC AR5 and AR6, this paper firstly summarizes the basic conceptions of emission metrics and their development in the past 30 years, then introduces the algorithms of common emission metrics of GWP and GTP in detail, finally gives the differences and applicability of the two metrics systematically. GTP is more closely related to global mean surface air temperature change, so it has potential advantages compared with GWP in evaluating the impact of greenhouse gases on surface air temperature. However, GTP also has some uncertainties, such as the influence of climate sensitivity factors, the heat exchange in the Earth system, and the selection of target time points. Then, the values of key emission indicators are summarized in the table for reference, including CO₂, CH₄, N₂O, HFC, CFC, PFC and aerosols. In addition, this paper also introduces some emerging emission metrics, such as Combined-GTP (CGTP) and GWP*. These new metrics are more precise, and more suitable for short-lived greenhouse gases.

This paper elaborates on the definition and origin of climate finance, analyzing its development, current status, challenges, and opportunities both domestically and internationally. Moreover, this paper explores how multilateral development banks are innovating in climate finance and discusses the lessons and value that can be learned from their approaches. Finally, the paper proposes seven recommendations to promote the future development of climate finance in China: improving the policy system of climate finance, establishing diversified financing channels, strengthening the construction of climate finance service systems, enhancing the application of digital technology, building a high-quality climate investment and finance project pool, exploring quantitative methods for climate finance, and intensifying international cooperation and exchanges.

The spatiotemporal heterogeneity at the onset of the Tibetan Plateau (TP) rainy season and its related evolutions of atmospheric circulation were investigated from 1979 to 2019 based on precipitation datasets from the surface observations and ECMWF. Results show that: (1) TP’s rainy season exhibits three precipitation centers respectively in the central-eastern, southern, and northern regions, with significant discrepancies in their rain process, precipitation concentration period, and precipitation. (2) There exists a bimodal distribution in the annual variation of precipitation over the central-eastern TP, with a remarkable increase around the 27th pentad. The onset of rainy season is accompanied by the weakened westerly stream in the mid-latitudes region, the convergence of the Southwest Monsoon from the Bay of Bengal and the west coast of Indian on the southern edge of the plateau, and the enhanced water vapor transport under southwestlies. However, an increase in precipitation appears at the 32nd pentad over the southern TP, manifesting an unimodal distribution. The corresponding atmospheric circulation pattern involves the northward movement of westerlies, convection development in the Indian Peninsula, and water vapor intrusion in the middle troposphere. In the northern TP, the annual change in precipitation is unimodal, and the increase in precipitation starts at the 29th pentad. The onset of its rainy season corresponds to the westward- and northeard-stretching of East Asian westerly jet, and intensive wind shear over the plateau. (3) It should be pointed out that water vapor flux at the onset of rainy season is mainly transported across the south and west boundaries in the central-eastern and southern subregions but north and west edges over the northern part of TP. The increases in the northward transport flux of water vapor and regional moisture budgets in the plateau region jointly have contributed to an earlier onset of the TP rainy season in the past decades.

China is currently facing the dual challenge of addressing climate change and achieving the goal of building a Beautiful China. Synergizing pollution reduction and carbon reduction has become an inevitable choice. This study focused on one of the most representative greenhouse gas control policies: the Carbon Emissions Trading Scheme. Based on panel data from 267 prefecture-level cities in China from 2007 to 2017, the carbon emissions trading pilot was regarded as a quasi-natural experiment. A mixed model with a combination of difference-in-differences method and fixed effects was constructed to analyze the effects of the carbon market pilot on carbon emissions reduction and pollution control. The results indicate that the carbon market polit has effectively reduced carbon emissions and decreased carbon intensity in the pilot areas, while also reducing industrial sulfur dioxide emissions and PM_2.5 concentrations. However, it does not have a significant impact on industrial wastewater and industrial particulate matter emissions. In regions with stricter penalty mechanisms and higher fiscal dependence, the synergistic effect of pollution and carbon reduction is more significant. From the perspective of market mechanisms, trading volume, carbon price, and trading days do not have an impact on pollution and carbon reduction.

The direct carbon dioxide emissions generated during the operation phase of high-speed railway transportation are minimal. However, the carbon emissions from electricity generation, required to power the trains, cannot be overlooked. This paper comprehensively considers the power generation structure and the carbon emissions levels of different power generation methods. It uses the carbon emission factor during the operation phase of high-speed railway transportation as an assessment indicator of its environmental friendliness. The results indicate that in 2018 and 2019, the carbon emission factors during the operation phase of high-speed railway transportation in China were 27.19 and 27.09 g CO₂ per passenger-kilometer, respectively. High-speed railway transportation has more advantages in terms of low carbon than road and civil aviation. Besides, the high proportion of coal-fired power generation in China’s power structure results in higher carbon emission factors compared to developed countries such as France, Germany, and Japan. By combining predictions of China’s future power generation structure, when the carbon emission factors of each power generation mode remain unchanged, it is estimated that by 2030 and 2050, the carbon emission factors during the operation phase of high-speed railway transportation in China will be 10.87-14.18 and 2.83-9.49 g CO₂ per passenger-kilometer respectively, representing a reduction of 47.66%-59.87% and 64.97%-89.55% compared to 2019. Reducing coal-power carbon emission factor will synchronize with carbon diminution of high-speed railway. Promoting low-carbon production of coal-power and efficiently applying new technologies for clean production are expected to further enhance the low-carbon advantages of high-speed railway transportation. The research results promote the cooperation between transportation industry and energy industry, and boost the “dual carbon” goals.

The 28th Conference of the Parties to the United Nations Framework Convention on Climate Change (COP28) completed the first Global Stocktake under the Paris Agreement. The assessment of the overall progress of pre-2020 global climate action is an indispensable component of this Global Stocktake. Whether to fulfill the pre-2020 climate commitments is the foundation for promoting the sustained and effective implementation of the Paris Agreement and carrying out post-2020 climate action. However, there is still a significant gap between the current global climate action and the long-term goals of the Paris Agreement. Developed countries have not effectively fulfilled their pre-2020 emission reduction commitments under the Cancun Agreement, and developing countries have proposed Nationally Appropriate Mitigation Actions (NAMAs), but it is difficult to assess the general progress in fulfilling these NAMAs. In addition, when developed countries were implementing their pre-2020 mitigation actions, there were some problems, including their mitigation targets were less ambitious, some conturies already achieved part of the mitigation targets when they released the targets, their emission reduction mainly relied on the COVID-19 and the mitigation contribution by economies in transition (EIT) countries, and they failed to fulfill their commitments on financial support and emission reduction. Developing countries face technological barriers and information access barriers in obtaining low-carbon technology support from developed countries. With vigorously developing renewable energy and continuously promoting energy structure optimization, China has exceeded its 2020 climate target and achieved victory in Poverty Eradication in 2020, making great contributions to the global green and low-carbon transition. It is Recommended that all parties focus on concrete actions rather than empty slogans. In particular, developed countries should take the lead in strengthening actions and fill in the pre-2020 implementation gaps, and strengthening the financial, technological and capacity-building support for developing countries, so as to ensure that they contribute to global climate governance based on their national circumstances.

The Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC) serves as the focal point and benchmark for global climate governance. In 2023, global temperature broke instrumental records. The year-end COP28 broke all previous records of the conference, with over 80000 officially registered participants. As an essential platform for global climate governance, both the outcomes of the conference and the participants directly reflected the driving force behind climate governance and the trends of countries’ participation in global climate governance. The focus of China and the USA on global climate governance at the COP28 was explored through the analysis of previous COP participants and their compositions, as well as the delegation makeup of China and the USA at COP28, coupled with the climate policies and the current public perceptions of climate change in both countries. The results indicated that the climate policies and actions of both countries were relevant to the participation of their representatives at this COP. Due to the continuity of policies, the USA government reversed its passive stance during the Trump era and is now actively engaging in the conference. At this COP meeting, the USA focused on political efforts, with federal government officials as the primary participant group. China was actively engaged in political negotiation, and its conference delegated predominantly consist of experts from renewable energy and related technological fields. A review of China and the USA’ climate policies and public perception indicated that strengthened domestic climate policies and heightened public perception of climate change in both nations contributed positively to global climate governance.