As a major frontier scientific field in climate change research, climate change detection and attribution aim to reveal the causes of climate change and quantify the impact of external forcing on climate change. These issues are not only the core of scientific research on climate change, but also the hotspot and focus of the international negotiations on climate change. China started relatively late in the field of detection and attribution, but in the past decade, with the efforts of Chinese scientists, we have achieved a number of breakthroughs in the understanding of regional climate change and the attribution of extreme events in China, and made remarkable research progress in the field of detection and attribution of climate change in China. This review shows that since the middle of the 20th century, human activities, mainly greenhouse gas emissions, are the major driver of regional warming and changes in the frequency, intensity and duration of temperature extremes in China. Human activities have a clear influence on changes in extreme precipitation, and signals of human activity can also be found in changes in some types of drought. At century scale, anthropogenic signals can be detected in the change in both mean and extreme temperatures. For major high-impact extreme events, anthropogenic forcing increases the probability of hot extreme events and decreases the probability of cold extreme events. The attribution conclusions of human influence on heavy precipitation events, drought events and complex events have low consistency, and are affected by event definition and attribution methods, etc. It is still very difficult to assess the general conclusions on the extent of human activities’ influence on these events. In the future, it is necessary to strengthen the detection and attribution on changes in precipitation, drought, atmospheric circulation, compound events, etc., to understand and improve the reliability of extreme event attribution results.

From the perspective of the energy framework, related research on Earth’s energy budget, effective radiative forcing, climate feedback, and climate sensitivity is systematically reviewed. Since the 1980s, Earth’s energy budget has increased by 0.28-0.52 W/m², primarily due to a sustained reduction in reflected solar radiation at the top of atmosphere. This is a crucial factor driving global warming during this period. These changes in the energy balance are closely linked to anthropogenic forcings and their effects on the climate. The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) indicates that during the period of 1750-2019, the best estimate of total anthropogenic effective radiative forcing is (2.72±0.76) W/m², which is projected to result in a global surface temperature increase of approximately 1.29 (1.00-1.65) ℃. Overall, climate feedback can offset the comprehensive disturbance caused by radiative forcing to the Earth system, helping to stabilize the climate state. The best estimate of net feedback provided by IPCC AR6 is -1.16 (-1.81--0.51) W/(m²·℃). To project future climate change, the IPCC AR6 provides best estimates for equilibrium climate sensitivity and transient climate response as 3.0℃ and 1.8℃, respectively, with very likely ranges of 2.0-5.0℃ and 1.2-2.4℃. Based on the forcing-feedback framework under the energy budget balance, the scientific community has clarified the impact of external forcings, such as anthropogenic and natural factors, on climate change by quantifying the Earth’s energy budget and its long-term changes, and by distinguishing between radiative forcing and climate feedback. Based on the best estimates of climate feedback parameters and climate sensitivity, the magnitude of the climate response to forcing can be quantified, enabling reasonable projections of the future climate.

In order to respond to climate change and to conduct systematic globalized observations of atmospheric constituents and their related physical and chemical properties, the Chinese government, in cooperation with the WMO and the United Nations Global Environment Facility (GEF), established the first global atmospheric baseline observatory (the Waliguan Baseline Observatory) in the Eurasian hinterland at Waliguan Mountain, Qinghai province, in September 1994, and has also conducted long-term observations of key atmospheric constituents, including greenhouse gases, aerosols, ozone, radiation, and acid rain, which are closely related to weather, climate, the environment and human health. After 30 years of construction and development, the Waliguan Baseline Observatory has accumulated a large amount of first-hand and globally representative atmospheric background observational data, which provide fundamental support for in-depth research, assessment and prediction of changes in atmospheric composition and their impacts on weather and climate changes, and also serve as an early warning and monitoring of future changes in atmospheric composition. This paper systematically reviews the Waliguan Baseline Observatory’s development history, major observing programs, and research results over the past 30 years. It also looks forward to future development direction and research focus.

Subalpine forests, playing an important role in maintaining biodiversity and regional water and carbon balance, are highly sensitive to global climate changes. In the context of global climate change, response and adaptation of subalpine forests are among the key scientific issues of terrestrial ecosystems. Tree growth is an important reflection of changes in forest ecosystems. This paper summarizes the diverse patterns of subalpine tree growth along altitudinal gradients, and sums up potential mechanisms underlying the different growth responses of subalpine trees, which included “temperature and precipitation effect hypothesis”, “carbon supply limitation hypothesis”, “carbon utilization limitation hypothesis” and “the influence of underground ecological processes”. Finally, the shorting-comings of these existing hypothesizes are discussed, the importance of hydraulics character of trees in regulating ecological processes is disclosed, and the future research directions are prospected.

The glacier is one of the most important components of the cryosphere, and the glacier mass balance is the most direct response to climate change. The Qinghai-Tibet Plateau (QTP) is known as the “Water Tower of Asia”. It is important to explore changes in the mountain glacier mass balance in the plateau to assess changes in sea level and water resources and provide early warning of the risk of ice-snow disaster. As a result of the “plateau amplification effect”, the QTP is warming at a rate higher than the global average. It continues to warm, and the plateau climate is becoming warmer and more humid. The westerlies and monsoon are the determining factors of climate and environmental change on the QTP; the glaciers in the monsoon-influenced area retreat strongly, the glaciers in the westerlies influenced area tend to stable or even advance in part of the glaciers, and the degree of glacier retreat in the westerlies-monsoon transition area is weakened. The loss of glacier mass is accelerated in the south-east of the QTP, while the shrinkage rate of the north-west glaciers is smaller, and the total glacier area will continue to decrease in the future. Most of the glaciers on the QTP are more sensitive to temperature changes than to precipitation, and extreme weather and large-scale circulation also have an important influence on changes in glacier mass balance, but research on the mechanism of their influence needs to be further strengthened. Researching changes in glacier mass balance in the QTP still faces many challenges and is a future frontier scientific issue and priority for cryosphere science.

The medium- and long-term supply and demand structure of China’s hydrogen energy were simulated and predicted under different scenarios. Firstly, a baseline, positive, and enhanced scenarios were set up, and Low Emission Analysis Platform (LEAP) model was constructed to predict the medium- and long-term demand for hydrogen in transportation, industry, and construction terminal sectors under multiple scenarios. Secondly, the levelized cost of hydrogen (LCOH) for 8 types of hydrogen production methods that account for carbon emissions was calculated, and future cost trends were predicted based on cost learning curves. Lastly, a hydrogen supply structure optimization model was constructed with the objective of minimizing hydrogen production costs, and the proportion of various hydrogen production methods from 2025 to 2060 was derived, simulating the evolution of carbon emissions. In terms of consumption structure, the industrial sector dominates hydrogen consumption, accounting for 65% in the positive scenario in 2060, and transportation is an important point of growth for hydrogen consumption. In terms of supply structure, fossil energy-based hydrogen production will still be the main source in the short term, with CCS technology playing a significant transitional role, and a hydrogen supply structure dominated by green hydrogen will gradually form in the long term, with renewable energy-based hydrogen production expected to reach 75% by 2060. In terms of carbon emissions, thanks to the clean transformation of the hydrogen production industry structure, carbon emissions will decrease from 618 Mt in 2023 to 103 Mt in 2060, with more significant carbon emission reductions at key points in 2030 and 2060 compared to other times. Based on the above research results, policy suggestions are put forward to promote the high-quality development of China’s hydrogen energy industry.

Carbon metering is a fundamental means of implementing carbon emission dual control management and achieving the “Dual Carbon” goal. The industrial sector still has a relatively high carbon emissions ratio, and the structure and characteristics of industrial carbon emissions will maintain in the near future, so the effectiveness of the industrial facility carbon metering system should be further enhanced. The current industrial facility carbon metering methodology has the following shortcomings: carbon accounting methods still dominate the metering method, but the uncertainty of emission factors are high; the satellite and radar remote monitoring method of carbon emissions is affected by a lot of factors and there are many difficulties in reverse calculation; the continuous emission monitoring or on-site monitoring method has some implementation obstacles and high costs; emission verification is mainly manual and slow, and is easily affected by subjective factors. Therefore, a carbon metering methodology framework based on the digital combination of “Satellite-Radar-CEMS-Carbon Floating” is proposed, which clarifies the path for its implementation, including: promoting standardization of basic data monitoring and detection based on the international measurement transfer system; promoting scientific positioning of industrial carbon emissions by combining “satellite-radar” monitoring means and carbon emission data base; promoting precise calculation of industrial carbon emissions by combining CEMS and carbon emission flow simulation; innovating industrial carbon emission digital management to promote rapid verification of industrial carbon emissions; and completing the carbon metering system by applying it in multiple scenarios, fields, and levels. Finally, the time schedule and key tasks are proposed for the carbon metering methodology.

The decomposition plan and evaluation adjustment of carbon reduction targets are crucial for achieving China’s goals of carbon peaking and carbon neutrality. In this paper, a decomposition method was proposed considering the principles of fairness, efficiency, sustainability, feasibility, and differentiation. On this basis, a decomposition model considering the reference value and adjustment value was established. The adjustment value was determined by the weighted sum of six indicators, including carbon emissions of key projects, according to the decomposition principle. Secondly, a case study was conducted on the decomposition of carbon intensity reduction targets in Chengdu to various districts. The 14th Five-Year Plan period’s carbon intensity reduction targets for these districts were categorized into five levels: 19.0%, 19.5%, 20.0%, 20.5%, and 21.0%. Furthermore, an analysis was provided on the reasons behind the variations in carbon intensity reduction targets among different regions. Finally, to promote the implementation of the decomposition plan, an evaluation and adjustment mechanism was proposed to achieve the established carbon reduction goals.

The rapid acceleration of global warming has led to an increase in extreme weather events, resulting in widespread and highly destructive power outages and shortages that occur with alarming frequency. This has prompted concerns about the safe and stable operation of the power system. With the accelerated transition of new power system, the scale of climate-sensitive grid-connected renewable energy sources continues to expand rapidly, posing unprecedented challenges to the power system. Climate resilience has become an essential characteristic of the system, crucial to ensuring its safe operation and vital to promoting the low-carbon transition of energy resources and mitigating climate change. This paper provides a comprehensive overview of the current research status of climate resilience in power systems. It introduces a novel analytical framework for assessing climate resilience and explores the climate resilience characteristics of power resources at the source, grid, and load levels. Additionally, it highlights the challenges associated with enhancing climate resilience in power system operation and planning and outlines potential pathways. It is suggested to strengthen macro policy guidance on climate resilient power system, continuously reinforce basic theory research, innovate key technologies, optimize resource allocation, and improve management mechanisms to enhance the climate resilience of new power system through diversified ways.

Climate warming has greatly increased the instability of the climate system, which in turn intensified the induced climate extremes. A tipping point occurs when changes in a part of the climate system become self-sustaining without the need for an external driver. Crossing tipping point of climate tipping elements will have significant and wide-ranging impacts on the planet and its inhabitants, ranging from sea level rise unprecedented on human timescales to extreme weather that is uninhabitable and beyond the current capacity to adapt. Thus, for policymakers, the key question now is not only how to mitigate climate change, but also, increasingly, how to build resilience to cope with the irreversible effects of tipping points.

Starting from the basic concept of the tipping point, this paper systematically summarizes the status and trend of tipping elements in the climate system, comprehensively analyzes the tipping points of four tipping systems with global influence, namely the Amazon Rainforest, the Atlantic Meridional Overturning Current (AMOC), the Greenland Ice Sheet (GrIS) and the Antarctica Ice Sheet (AIS), and their possible cascading effects, especially the possible effects and threaten to China’s climate security. The analysis shows that the collapse of the Amazon Rainforest has a negative impact on the wind and light resources and the stability of the cryosphere in China, mainly through affecting the temperature and precipitation over the Qinghai-Tibet Plateau (QTP), while the collapse of AMOC has an impact on food production, mainly by influencing the patterns of Asian summer monsoon rainfall, and is likely to have adverse impacts on food security and energy security by raising regional sea level, intensifying land heat waves and coastal storm surges. The collapses of the GrIS and AIS impact on China not only through contributing to global sea level rise, which has a negative impact on marine and coastal ecosystems, but also through injecting more fresh water into the Atlantic and the Southern Ocean, hence contributing to the weakening of AMOC and the lower limb of the abyssal overturning circulation around Antarctica, which in turn affects climate anomalies, sea level height and the productivity of marine ecosystems that directly or indirectly affect food availability and diversity.

It should be noted that the crossing of tipping points by some low-temperature tipping elements, together with feedbacks from some non-tipping elements may push the global mean surface temperature even higher, triggering abrupt changes in tipping elements at higher temperature levels. Without greater efforts to control the level and rate of global warming, humanity will be put in high risks of tipping. However, we are unprepared for the potentially devastating consequences of climate tipping points, and there is an urgent need to develop the capacity to provide early warning of climate tipping points and ensure climate security to build sustainable and resilient societies.

Different from the existing early warning systems, early warning of tipping points requires the establishment of a “climate security early warning system”, which provides response suggestions based on long-term climate predictions and projections, so as to better help governments and communities develop long-term climate change adaptation and mitigation strategies and development plans, and mitigate the negative impacts of abrupt changes of climate system on social and economic structures. By analyzing the early warning signals of tipping points, this study points out the strategic importance of implementing early warning of climate tipping points for ensuring China’s climate security. Combined with the current scientific understanding of tipping points, it is proposed that the QTP can be the starting point for practicing early warning for climate security in China. Taking the QTP as the starting point, on one hand, increasing the research and cognition of the tipping state of the QTP, monitoring and evaluating precursor signals of tipping, and on the other hand, studying the upstream and downstream impacts of climate abrupt change over the QTP, and conducting graded early warning according to the prediction and projection results, should be an operational approach and priority for China to establish an early warning system for climate security and ensure climate security.

On the basis of the unified understanding that the climate system is becoming more and more extreme and the climate tipping point has posed a certain threat to human security, quantifying the tipping point of the QTP and its potential cascading impacts, and monitoring the early warning signals have become the key to establishing a climate security early warning system and realizing truly sustainable development. However, the QTP itself is a complex system, and the data problems caused by sparse ground-based observations, coarse reanalysis and model grids, and limited satellite life cycle make the current scientific understanding on the drivers, interactions and feedbacks of the physical processes on the QTP, such as the hydrothermal cycle and energy balance, insufficient. As a result, the applicability of the parameterization in the climate model is limited in this region, which brings challenges to the research, operational monitoring and decision-making services for the QTP climate tipping point and early warning indicators. To this end, the study puts forward three research suggestions: first, the use of artificial intelligence technology to accelerate scientific understanding of the Earth’s climate system, a typical complex system; second, leveraging the unique role of satellite remote sensing in supplementing space coverage to detect the changing resilience of vulnerable systems and identify the tipping points of the system; third, accelerating the development of physical and AI-driven models that can identify small warning signals and build the ability to detect climate tipping points on the QTP.

Action Plan for Carbon Dioxide Peaking Before 2030 proposes that “The Beijing-Tianjin-Hebei region, the Yangtze River Delta, and the Guangdong-Hong Kong-Macao Greater Bay Area etc. will play their roles as drivers and growth poles for China’s high-quality development and lead the way in promoting an overall green transformation of economic and social development”. To evaluate the climate action capability and progress of green and low-carbon development in the three key regions, and to help each region find a sustainable and high-quality development path that suits itself, a regional climate action capability evaluation system was established based on the Analytic Hierarchy Process, and a regional climate action capability index was set up. The comprehensive evaluation results show that the climate action index in the Yangtze River Delta region is the highest, followed by the Beijing-Tianjin-Hebei region and the Guangdong-Hong Kong-Macao area. The three major regions all have advantages and challenges compared to other regions. For example, the Beijing-Tianjin-Hebei region has the most outstanding performance in terms of dual carbon goals and policies, capacity building and security, the Guangdong-Hong Kong-Macao area has the most advantages in low-carbon development level, while the Yangtze River Delta is ahead of other regions in terms of regional synergy, low-carbon resource and industrial foundation. Policy recommendations have been formed such as strengthening the development of green and low-carbon industries, improving climate legislation and policies, and promoting the development of green finance, etc.