The development of the AMS 14C dating preparation laboratory has been completed in the Beijing Normal University. Two vacuum lines for sample combustion and hydrolysis and 4 graphitization systems were installed. One miniaturized pyrolysis-combustion device interfaced with online Infrared Gas Analyzer (IRGA) and Fourie Transfer Infrared Spectroscopy (FTIR) is connected to one vacuum system. The other vacuum system with 12 ports is used simply for evacuation. Total of 44 H2/Fe reactors with user friendly semi-automated operating systems have capability for a large sample throughput. Results of the graphitized blanks, intercomparison samples with 1 and 2 half-life of 14C, and OXII standards materials measured at the 1MV multi-element AMS system from the High Voltage of Engineering Europa at the BNU are discussed.

Black carbon, an important component of atmospheric aerosols, has an impact on climate change. When deposited on snow and ice, it reduces surface albedo, accelerating melting and amplifying global warming. Here, we analyzed lake sediment records from China and found that existing bottom-up inventories underestimate black carbon emissions prior to the mid-twentieth century. We incorporated a black carbon emission enhancement scheme based on reconstructed historical biomass burning emissions into a numerical climate model to assess this underestimation. The simulations indicated that increased historical emissions enhanced spring and summer radiative effects north of 60°N, leading to regional surface warming and accelerated Arctic snowmelt. Although the response varies with the strength of emission enhancement, the findings suggested that historical BC emission biases could alter the simulated Arctic energy balance and climate evolution. These results highlight the need for improved constraints on historical BC emissions to better assess their climate impacts. Increases in historical black carbon emissions enhanced spring and summer radiative effects north of 60°N, leading to regional surface warming and accelerated Arctic snowmelt, suggests a study combining climate modeling with lake-sediment records from China.

Soil organic carbon (SOC) comprises particulate (POC) and mineral-associated organic carbon (MAOC), which differ in formation, stabilization, and loss mechanisms. While the current global distribution of POC and MAOC is characterized, their vulnerability under future climate scenarios remains unclear. Using 3284 topsoil (0-30 cm) observations from six continents, we identify high-latitude soils as global hotspots of SOC vulnerability under shared socioeconomic pathway scenarios (SSP126, SSP245, and SSP585). Under a high-emission scenario (SSP585), high-latitude soils are projected to lose substantial POC by 2100, accounting for about 81 ± 10% of total SOC losses. These declines are driven by the high proportion of SOC stored as POC (fPOC) and its high temperature sensitivity. We show that fPOC is a robust indicator of SOC vulnerability to climate change. Globally, the projected POC decline corresponds to a cumulative carbon dioxide (CO2) release of 81.34 Pg CO2-equivalent by 2100, highlighting the importance of preserving POC to mitigate climate feedbacks.

Water resources are crucial for the survival and development of human societies in arid Central Asia. However, our understanding of regional hydroclimate variability and moisture dynamics remains limited. Here, we present a precisely dated, high-resolution speleothem δ18O record from caves in northern Uzbekistan that reconstructs changes in precipitation δ18O over the last 47,000 years. During the glacial interval, relatively low speleothem δ18O values align with precipitation isotope records from high northern latitudes. The close correspondence between the Uzbekistan record and Greenland ice-core δ18O during Heinrich Stadial 1 indicates a strong temperature control on regional precipitation δ18O, although Dansgaard-Oeschger-scale variability is weakly expressed. During the Holocene, speleothem δ18O reached minimum values near 8 ka BP and then increased toward the present, broadly consistent with records from southern Uzbekistan and the Asian monsoon region, but with less coherent centennial- to millennial-scale variability. Supported by model simulations, we propose that during the glacial and mid-Holocene, when winter temperatures were low, the regional precipitation was dominated by northerly and northwesterly moisture transport linked to enhanced high-latitude temperature gradients and southward-shifted westerlies. In contrast, late Holocene hydroclimate increasingly reflected southerly to southwesterly cyclonic moisture transport from the eastern Mediterranean and the Near East, driven by northward-shifted westerlies. These results show that arid Central Asian hydroclimate and precipitation δ18O have been shaped by the position and strength of the westerlies through major reorganizations in moisture-source trajectories, with direct implications for understanding future water availability as subtropical and temperate circulation zones shift northward.

Loess deposits from the Kunlun Mountains provide high-resolution eolian dust archives that allow us to understand past dust emission patterns in the Asian interior, and associated abrupt atmospheric circulation changes during the glacial-Holocene transition. Coarse-grained particles from this area (site AQ16) offer evidence of frequent dust plumes on millennial to centennial timescales in the Tarim Basin. Abrupt dust flux fluctuations during this transition, particularly during the Younger Dryas (YD), exhibit co-variation patterns similar to those seen in dust records from West Asia, East Asia, and Greenland, suggesting intercontinental climate teleconnections through the boreal westerly jet. We observe an anomalously high dust flux during the YD, not correlated with grain size. We attribute this circumstance to a stagnant westerly jet over the Tarim Basin for an extended period, leading to a prolonged duration of dust events. This could be due to a weakened Atlantic Meridional Overturning Circulation that triggered a southward shift and strengthening of the westerly jet, in conjunction with the North Atlantic Oscillation. These findings have broad implications for understanding regional dust emission dynamics and the coupling between dust emissions and atmospheric circulation on a global scale during the transition from the last glacial to the early Holocene.

Given growing concerns about global climate change, it is critical to understand both historical and current shifts in the hydroclimate, particularly in regions critically entwined with global circulation. The Tibetan Plateau, the Earth’s largest and highest plateau, is a nexus for global atmospheric processes, significantly influencing East Asian hydroclimate dynamics through the synergy of the Asian Monsoon and the Westerlies. Yet, understanding historical and recent hydroclimate fluctuations and their wide-ranging ecological and societal consequences remains challenging due to short instrumental observations and partly ambiguous proxy reconstructions. Here, we present a precisely-dated 3476-year precipitation reconstruction derived from tree-ring δ18O data on the Tibetan Plateau, representing one of the few multi-millennia-long annually-resolved terrestrial δ18O records to date. Our findings reveal that the 20th century drought extremes are severe within the past three millennia, and likely linked to the weakening of both the Asian Monsoon and Westerlies due to anthropogenic aerosol emissions. Additionally, our analyses identified three distinct stages (110 BC–AD 280, AD 330–770 and AD 950–1300) characterized by shifts toward arid hydroclimate conditions, corresponding to significant social unrest and dynasty collapses, which underscores the potential societal impacts of severe hydroclimatic shifts. An annually resolved 3476-year tree-ring record from the Tibetan Plateau reveals severe 20th century droughts and highlights the interplay between the Asian Monsoon and Westerlies. Droughts are often linked to the collapse of dynasties.

Speleothem δ18O records from central southern China have long been regarded as a key benchmark for Asian summer monsoon intensity. However, the similar δ18O minima observed among precession minima and their link to seasonal precipitation mixing remains unclear. Here, we present a 400,000-y record of summer precipitation δ18O from loess microcodium, which captures distinct precession cycles similar to those seen in speleothem δ18O records, particularly during glacial periods. Notably, our microcodium δ18O record reveals very low-δ18O values during precession minima at peak interglacials, a feature absent in speleothem δ18O records from central southern China. This discrepancy suggests that the mixed summer and nonsummer climatic signals substantially influence the speleothem δ18O records from central southern China. Proxy-model comparisons indicate that the lack of very low-δ18O values in speleothem δ18O records is due to an attenuated summer signal contribution, resulting from a lower summer-to-annual precipitation ratio in southern China at strong monsoon intervals. Our findings offer a potential explanation for the long-standing puzzle of the absence of 100- and 41-kyr cycles in speleothem δ18O records and underscore the critical role of seasonality in interpreting paleoclimatic proxies in central southern China. These insights also have broader implications for interpreting speleothem δ18O records globally, advocating for a more multiseason interpretive framework.

The manner in which the climate over arid central Asia (ACA) changes in a warming world is an important issue. Due to the region’s complex terrains, most climate models do not perform well in the area. Here, we utilize high-resolution ( 50 km) and PMIP4 simulations to assess the mid-Holocene precipitation changes over the ACA. The results show that only 4 of the 15 models have captured the basic precipitation seasonality over the summer-precipitation-dominated sub-region. Among them, only the high-resolution CESM and the IPSL-CM6A-LR have successfully simulated the summer precipitation dipole. A significant increase occurs in the Tarim Basin, while a decrease takes place across the regions north of the Tianshan Mountains, which is consistent with multi-proxy records. The northern drying is primarily linked to the adjusted wave trains along the weakened mid-latitude westerlies. In contrast, the southern moisture stems from enhanced monsoon penetration into the Tarim Basin, driven by the enhanced Tianshan heat source. This monsoon intrusion in models depends significantly on the strengthened Tianshan heating; thus, the Tianshan heat source is a key factor in shaping the regional hydroclimate, which should be taken seriously in climate models.

How terrestrial mean annual temperature (MAT) evolved throughout the past 2 million years (Myr) remains elusive, limiting our understanding of the patterns, mechanisms, and impacts of past temperature changes. Here we report a ~2-Myr terrestrial MAT record based on fossil microbial lipids preserved in the Heqing paleolake, East Asia. The increased amplitude and periodicity shift of glacial-interglacial changes in our record align with those in sea surface temperature (SST) records. However, its long-term warming trend (1.0 °C/Myr, 95% CI = 0.4-1.7 °C/Myr) during 1.8-0.6 Myr ago diverges from the contemporaneous SST cooling. We propose that the Pleistocene warming in East Asia primarily resulted from regionally enhanced heat input and greenhouse effect of rising water vapor driven by Antarctic ice sheets (AIS) growth, highlighting the important climatic effect of AIS evolution. Such long-term warming across the Mid-Pleistocene Transition might have been beneficial for archaic humans' flourishing in Eurasia.

Soil organic carbon (SOC) is primarily categorised into particulate organic carbon (POC), derived from plants' activities with high decomposition rates, and mineral-associated organic carbon (MAOC), originating from microbial processes characterised by low decomposition rates. However, the interplay of climate, vegetation, and soil properties influencing the regional distribution and driving mechanism of POC and MAOC remains inadequately understood. This study comprehensively analysed topsoil POC and MAOC over the Yellow River Basin (795,000 km2) in northern China, assessing the influence of climatic, vegetative, and pedological variables on these soil carbon forms. Our results reveal that the concentrations of MAOC (average 5.59 g kg- 1) exceeded POC (average 3.05 g kg- 1) across the basin. Spatially, both POC and MAOC levels (5.25 g kg- 1 and 9.74 g kg- 1) were greater in the western part of the basin compared to the east (3.77 g kg- 1 and 5.28 g kg- 1), and topsoil SOC stability (45.32 %) was greater in the southern region than in the north (68.24 %). MAOC exhibited a stronger correlation (R2 = 0.84) with SOC than POC (R2 = 0.57), suggesting its dominant contribution to the topsoil SOC pool. Furthermore, the results highlighted that soil pH and mean annual air temperature emerged as the primary factors influencing the distribution of both POC and MAOC across the basin. Climatic and vegetative factors indirectly shape the regional POC and MAOC distribution patterns by regulating soil properties. These insights underscore the necessity of distinguishing between POC and MAOC to improve our understanding and quantification of SOC distributional patterns, thereby clarifying the specific environmental conditions that influence these distinct carbon pools over the Yellow River Basin, which help to achieve the "dual carbon" strategic goal in China.

There has been a sharp rise in the extent and scale of human activities since the mid-20th century, termed the "Great Acceleration", and nuclear activities are one of the defining technological processes for this period. 239,240Pu released by atmospheric nuclear weapons tests provides an ideal chronostratigraphic marker for labeling this change due to its global fallout feature, temporal mutation, and long half-lives. However, the accumulation dynamics of plutonium from atmospheric deposition to preservation in the sediment is still controversial. Three sediment cores collected from two maar lakes with high-quality chronology were analyzed for 239,240Pu. The first high-yield thermonuclear test (31st October 1952) and the highest global tests in 1961-1962 were identified, respectively, as the first rapidly increased 239,240Pu in 1953 and peaked in 1963. In anoxic Lake Sihailongwan (SHLW), scavenging Pu from the water to sediment was accelerated due to the major particulate associated forms of Pu(III) and Pu(IV) and rapidly elevated dust flux when ice-melting occurred in every spring. The desorption of Pu from beneath sediment to the lake water and resorption by sediment particles were stronger in shallow and oxic Lake Huguangyan. Therefore, the first rapid increase of 239,240Pu in 1953 and peak in 1963 accompanied by rapid scavenging and well preservation of plutonium provide a robust time marker for the "Great Acceleration", and this marker nearly permanently exists in such kind of lake sediment similar to Lake SHLW.

Leaf wax n-alkanes have been widely used to indicate past changes of hydroclimates. However, the responses of hydrogen (delta H-2(wax)) and carbon isotopes (delta C-13(wax)) of leaf wax n-alkanes to hydroclimates still remain unclear. In this study, we systematically investigated leaf wax n-alkane compounds such as n-alkanes, delta H-2(wax), and delta C-13(wax) values in modern plants throughout the spatial Chinese Loess Plateau (CLP; similar to 640, 000 km(2)) across different seasons (spring, summer, autumn), and analyzed the relationships between delta H-2(wax) and delta C-13(wax) values and hydroclimatic factors. Our results showed that, over the regional-scale CLP, the effects of plant types on leaf wax n-alkanes were prominent, but the seasonal differences became muted. These finding indicates that plant type effects should be considered, but seasonal variations might be ignored, when leaf wax n-alkanes were used to reconstruct paleohydroclimates on the CLP. Additionally, the isotopic apparent fractionations (epsilon(app) values for delta H-2(wax); epsilon(wax/bulk) values for delta C-13(wax)) also showed consistent plant type effects, highlighting differences of epsilon(app) values between dicots and monocots and discrepancies of epsilon(wax/bulk) values between C-3 and C-4 plants. Considering plant type effects, delta H-2(wax) and delta C-13(wax) values from the CLP were consistent with expectations from the global contexts, and they well responded to hydroclimatic factors (temperature and precipitation). The delta H-2(wax) values in both dicots and monocots likely responded mainly to temperature, but delta C-13(wax) values in C-3 plants primarily reflected precipitation whereas delta C-13(wax) values in C-4 plants primarily reflected temperature. These findings indicate that delta H-2(wax) and delta C-13(wax) values have great potentials as proxies for paleotemperature and paleoprecipitation on the CLP and globally.

Observational and modeling results show that the frequency and amplitude of extreme climatic events have increased significantly in the context of global warming. However, whether abrupt climate changes intensified during past warm periods remains poorly constrained due to the lack of high-resolution geological records. Here, we report a 512-m predominantly lacustrine sedimentary record from the Weihe Basin (North China), revealing that lake levels fluctuated significantly on suborbital (half- and quarter-precession) and millennial timescales over the last 2 Ma. Grain-size results reveal that magnitudes of rapid lake level fluctuations increased dramatically during Pleistocene interglacials, differing from glacial amplification of abrupt climate events recorded in North Atlantic marine sediments. Model results indicate that summer insolation maxima in low-latitude region of both hemispheres can lead to intensified monsoon precipitation in East Asia. Our proxy-model comparison highlights the importance of low-latitude bihemispheric insolation maxima in driving millennial-scale hydroclimatic variability in a warming future.

Hydroclimatic change in the Asian interior plays a key role in regulating regional environmental sustainability, water security, and human-nature relationships. However, the influence of the summer monsoon and westerly circulation on the evolution of hydroclimate over the arid Asian interior remains controversial. Here we present newly collected hydroclimate proxies from loess in the Asian interior, together with transient model simulations, to address the coevolution of monsoon-induced extreme rainfall and significant westerly-affected drying during the mid-Holocene. Our results suggest that a drier mid-Holocene in the southern Tarim Basin was associated with a poleward displacement of the westerly jet due to relatively warm boreal summer temperatures in the mid-latitudes. Strengthened water vapor fluxes associated with the boreal summer monsoon facilitated extreme rainfall events and enhanced mountain erosion. Our proxy-model comparison reveals a drier westerly regime superimposed with strengthened rainfall over the Asian interior during the warm mid-Holocene. Our findings suggest that more summer flash rainstorm events are likely to occur in a warmer world, with enhanced drying in the hyper-arid Asian interior. Mid-Holocene dry climate in the Asian interior was associated with the poleward displacement of the westerly jet due to warm boreal summer temperatures at mid-latitudes, according to hydroclimate, radiocarbon and paleoclimate data and transient model simulations.

Wildfires release large amounts of greenhouse gases into the atmosphere, exacerbating climate change and causing severe impacts on air quality and human health. In this study, based on a bottom-up approach and using satellite data, combined with emission factor and aboveground biomass data for different vegetation cover types (forest, shrub, grassland, and cropland), the dynamic changes in CO2 emissions from wildfires in China from 2001 to 2022 were analyzed. The results showed that between 2001 and 2022, the total CO2 emissions from wildfires in China were 937.7 Tg (522.6–1516.0 Tg, 1 Tg = 1012 g), with an annual average of 42.6 Tg (23.8–68.9 Tg). The CO2 emissions from cropland and forest fires were relatively high, accounting for 45 % and 46 % of the total, respectively. The yearly variation in CO2 emissions from forest and shrub fires showed a significant downward trend, while emissions from grassland fires remained relatively stable. In contrast, the CO2 emissions from cropland fires showed an upward trend, primarily in Northeast China. Hot spot analysis and geographically and temporally weighted regression (GTWR) models revealed significant spatial heterogeneity in emissions across vegetation types. Persistent hot spots of shrub and forest fires were located in Southwest and South China, while Northeast China experienced sporadic but extreme fire events. The GTWR model for shrub fire CO2 emissions exhibited the highest predictive performance (R2= 0.87), and climatic factors (particularly temperature and humidity) were the main influencing factors. Notably, the recent rise in cropland fire CO2 emissions in Northeast China is closely linked to region-specific straw-burning policies. The research results provide valuable references for atmospheric transport models, regional fire management, and national carbon accounting frameworks in the context of climate change.

The 1 MV multi-element AMS system at Beijing Normal University, built by High Voltage Engineering Europa B.V., is now commissioned after some delay. This advanced 1 MV system is uniquely configured to accommodate low background analyses of all elements from tritium to actinides, including an additional detector line dedicated to beryllium ion detection with improved overall ion transmission efficiency. For the main detector line, both the low- and high-energy magnet chambers are electrically insulated so that a rapid sequential isotope selection mode can be used for measuring actinide isotopes at similar to 1 Hz cycling rate. In this report, data covering Be-10, C-14, Al-26, Ca-41, I-129, Pu-239,Pu-240 and U-236 from the recently completed on-site acceptance tests are presented. The initial experiences with routine radiocarbon analyses are also reported.

A mechanistic understanding of the interacting processes governing the ecohydrological cycle is of paramount importance for comprehending the soil-plant-atmosphere continuum (SPAC) in the Critical Zone. The analysis of these processes may necessarily consider the different water types that characterize ecohydrological flux exchanges at the catchment scale but, so far, few studies have disentangled functional interactions among various water types within the Critical Zone. This study leveraged three years of isotope data (delta O-18 and delta H-2) collected from twelve water sources, including precipitation, throughfall, snow, stream water, groundwater, dew water, frost water, mobile and less-mobile soil water, root water, stem water, and leaf water in two catchments with distinct land cover (forestland versus grassland) on the Chinese Loess Plateau (CLP). We infer the main ecohydrological processes controlling water exchange in the Critical Zone under the contrasting vegetation covers. Our results showed new interactions among the several investigated water types, and in particular highlighted that: i) The seasonal isotopic variation in precipitation played a critical role in the seasonal isotopic patterns observed in other water types; ii) Dew water significantly contributed to leaf water uptake, more in forestland (26 +/- 6 %) than in grassland (16 +/- 11 %). Snow and groundwater were more influential for root water of shrubs and grasses in forestland (59 +/- 34 % and 16 +/- 8 % for snow and groundwater, respectively) than in grassland (36 +/- 26 % and 6 +/- 6 %) and they were very important for stem water of trees in forestland (84 +/- 14 % and 45 +/- 22 % for snow and groundwater, respectively); iii) Isotopic values in mobile and less-mobile soil water differed significantly between forestland and grassland (p < 0.05), but those in plant water (root, stem, and leaf water) did not differ significantly (p > 0.05); and iv) There were dynamic exchanges between mobile and less-mobile soil water, and between groundwater and soil water on the CLP. All these observations allowed us to establish a new isotope-based conceptual model of the ecohydrological cycle in the Critical Zone of the CLP that provides the foundation for future research and sustainable water resource management in this region.

Poyang Lake is the largest freshwater lake in China, yet mechanisms controlling its storage capacity variations remain poorly investigated. Here we show that lake storage capacity dynamics are mainly driven by jacking force and outlet channel erosion, based on 39-year daily in situ observations (1980-2018). A lower water level at the lake outlet and a diminished jacking force in the Yangtze River can be attributed to the upstream dams storing water between August and October; consequently, more water from Poyang Lake flows out, causing the impairment of storage capacity. Furthermore, channel degradation near the outlet is likely due to the severe sand mining and hungry-water-driven Yangtze channel erosion, the latter of which implies an enhanced outlet channel scour. As a result, the lake storage capacity has been substantially weakened. Our findings further the understanding of the downstream lake storage capacity responses to dam operation and human activities and have important implications for lake ecology and flood management in large dammed river-lake systems.

Multiple lines of observational evidence have indicated a significant wetting over the arid and semi-arid Northwest China (NWC) during recent decades, coinciding with a simultaneous sharp decline of dust events. Although recent studies have attributed NWC wetting to different anthropogenic and natural forcings, the mechanisms are not definitive and the regional wetting has been greatly underestimated in the Coupled Model Intercomparison Project historical simulations. Based on sensitivity experiments with different dust emission amounts using the NCAR Community Atmospheric Model version 5 (CAM5), here we find that decreasing dusts exert significant impacts on mixed-phase clouds through reducing the concentration of ice nucleating particles, increase the NWC precipitation and thus induce regional wetting through enhancing convection precipitation. A possible convection invigoration mechanism whereby the atmospheric vertical temperature gradient and convective instability are strengthened by reduced dusts, leading to convection invigoration and increased precipitation. These results are reinforced by simulations over the dust region in North Africa where mixed-phase and ice clouds are rare and reduced dusts do not increase precipitation. This study highlights the possible mechanism of dust-ice cloud interactions in recent NWC wetting and future regional climate change.

This is the Executive Summary of a report produced by the membership of the Anthropocene Working Group as part of a submission to the Subcommission on Quaternary Stratigraphy to seek formalisation of the Anthropocene as an epoch of geological time. It summarises the content of two reports and their associated appendices which provide a background to: the history of usage of the term Anthropocene, when the proposed epoch started, the characterisation of the Anthropocene geological deposits and their stratigraphic value, the recognition of the Anthropocene in different sedimentary environments, the rank and duration of the Anthropocene, the proposed Global boundary Stratigraphic Section and Point and supporting Standard Auxiliary Boundary Sections.