Barchans of Minqin:quantifying migration rate of a barchan

The migration speed of a typical barchan on the border of Minqin oasis,Gansu Province,northwestern China,was estimated by means of two methods.One is on the basis of a simple physical model and short-term field measurements.The other comes from the combination of the barchan internal structure detected by ground-penetrating radar and optical/radiocarbon dating techniques.The upper limit of migration speed given by conventional C-14 dating is 3.42 m/yr.The optically stimulated luminescence dating indicates that the time-average migration speed of the studied barchan was 1.78 m/yr in 28 years prior to 2007.The physical estimation further suggests that the annual migration speed has increased in recent years.

Coupled Pacific Rim megadroughts contributed to the fall of the MingDynasty’s capital in 1644 CE

Historical documents provide evidence for regional droughts preceding the political turmoil and fall of Beijing in 1644 CE,when more than 20 million people died in northern China during the late Ming famine period.However,the role climate and environmental changes may have played in this pivotal event in Chinese history remains unclear.Here,we provide tree-ring evidence of persistent megadroughts from1576 to 1593 CE and from 1628 to 1644 CE in northern China,which coincided with exceptionally cold summers just before the fall of Beijing.Our analysis reveals that these regional hydroclimatic extremes are part of a series of megadroughts along the Pacific Rim,which not only impacted the ecology and society of monsoonal northern China,but likely also exacerbated external geopolitical and economic pressures.This finding is corroborated by last millennium reanalysis data and numerical climate model simulations revealing internally driven Pacific sea surface temperature variations and the predominance of decadal scale La Ni?a-like conditions to be responsible for precipitation decreases over northern China,as well as extensive monsoon regions in the Americas.These teleconnection patterns provide a mechanistic explanation for reoccurring drought spells during the late Ming Dynasty and the environmental framework fostering the fall of Beijing in 1644 CE,and the subsequent demise of the Ming Dynasty.

Reconciling East Asia’s mid-Holocene temperature discrepancy through vegetation-climate feedback

The term“Holocene temperature conundrum”refers to the inconsistencies between proxy-based reconstructions and transient model simulations,and it challenges our understanding of global temperature evolution during the Holocene.Climate reconstructions indicate a cooling trend following the Holocene Thermal Maximum,while model simulations indicate a consistent warming trend due to icesheet retreat and rising greenhouse gas concentrations.Various factors,such as seasonal biases and overlooked feedback processes,have been proposed as potential causes for this discrepancy.In this study,we examined the impact of vegetation-climate feedback on the temperature anomaly patterns in East Asia during the mid-Holocene(~6 ka).By utilizing the fully coupled Earth system model EC-Earth and performing simulations with and without coupled dynamic vegetation,our objective was to isolate the influence of vegetation changes on regional temperature patterns.Our findings reveal that vegetation-climate feedback contributed to warming across most of East Asia,resulting in spatially diverse temperature changes during the mid-Holocene and significantly improved model-data agreement.These results high-light the crucial role of vegetation-climate feedback in addressing the Holocene temperature conundrum and emphasize its importance for simulating accurate climate scenarios.

The δ^(15)N values of foxtail millet(Setaria italica)and common millet(Panicum miliaceum)are reliable indicators of manuring practices

Millet agriculture,which originated in northern China,alongside rice agriculture,have nurtured the Chinese civilization.Prehistoric manuring practices likely promoted and maintained sustainable millet agricultural production in the loess area of northern China.However,ongoing controversy exists regarding the indicators of prehistoric manuring intensity of foxtail millet(Setaria italica)and common millet(Panicum miliaceum).Here,we present the results of pot and field fertilization experiments on two millet types.Our findings suggest that manuring can significantly increase the δ^(15)N values of foxtail millet,and its δ^(15)N values increase with increasing manuring levels.The δ^(15)N values of foxtail millet leaves are systematically greater than those of grains by approximately 1.6‰.Manuring could have a long-term residual impact on increasing the δ^(15)N values of soil and millet crops.Combined with previous crop fertilization experiment results,we propose that the impact of manuring on the δ^(15)N values of non-nitrogen-fixing crops is roughly consistent.The δ^(15)N value and amount of manure are key factors determining the extent of change in plant δ^(15)N values.The millet grain δ^(15)N values can serve as reliable indicators of manuring practices.Finally,we provide an interpretive framework for assessing the correlation between manuring levels and the δ^(15)N values of archaeological millet remains.The δ^(15)N values of ancient millet grains suggest widespread and intensive manuring practices in prehistoric millet agriculture in northern China,spanning from the early Yangshao period to the Longshan period.

Evidence of hybridization of cattle and aurochs on the Tibetan Plateau3750 years ago

Wild aurochs(Bos primigenius)were once widespread across Eurasia and North Africa but became extinct around the 17th century[1].Aurochs are considered the ancestor of modern taurine(B.taurus taurus)and indicine(B.t.indicus)cattle,which were independently domesticated within regions restricted to Southwest Asia and South Asia,respectively[2,3].Extensive gene flow from local aurochs to domestic cattle has been well documented in Southwest Asia,Europe,and Africa[3,4],raising questions about the mechanisms underlying both the domestication and dispersal of early cattle.

Spatial heterogeneity in the formation of large deserts in midlatitude Asia revealed by drill core evidence

Deserts are the most distinctive landscapes in the arid zones of midlatitude Asia,producing over 600 Tg of dust annually and serving as primary sources of mineral dust for the Northern Hemisphere.This dust is carried by the westerlies and the East Asian winter monsoon to downwind regions including East Asia,the northern Pacific Ocean,and even Greenland,influencing the global climate,global biogeochemical cycles,ocean productivity,Northern Hemisphere glaciations,and human health.

“Mega-sandwich pattern”of interdecadal precipitation variations and its regional manifestation in the Asian summer precipitation region

The Tibetan Plateau(TP)is an important link between the South Asian monsoon(SAM)region,the East Asian monsoon region,and the drylands of Central Asia.Climate changes within these regions are dominated by both the monsoon and the westerlies.This has prompted the scientific community to adopt a broad spatial perspective,proposing concepts such as the"Pan-Third Poleoor"Asian summer precipitationo,to better understand the regional climate dynamics,their driving mechanisms,and the resulting major ecological and environmental impacts.

Estimation of China’s terrestrial ecosystem carbon sink:Methods,progress and prospects

China announced its national goal to reach the peak of carbon emission by 2030 and achieve carbon neutrality by 2060,during the General Assembly of the United Nations in September 2020.In this context,the potential of the carbon sink in China’s terrestrial ecosystems to mitigate anthropogenic carbon emissions has attracted unprecedented attention from scientific communities,policy makers and the public.Here,we reviewed the assessments on China’s terrestrial ecosystem carbon sink,with focus on the principles,frameworks and methods of terrestrial ecosystem carbon sink estimates,as well as the recent progress and existing problems.Looking forward,we identified critical issues for improving the accuracy and precision of China’s terrestrial ecosystem carbon sink,in order to serve the more realistic policy making in pathways to achieve carbon neutrality for China.

Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects

The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective.

Early human occupation of the Tibetan Plateau

The Tibetan Plateau,the world's "Third Pole",has an average elevation above 4,000 masl (meters above sea level)and an area of over 500×10^4km^2,It is the highest and largest plateau on earth and is very sensitive to global climate change [1,2].The cold,dry and hypoxic high-altitude environment of the plateau presents a major challenge to human survival.Therefore,the history and mechanisms of prehistoric human history on the Tibetan Plateau-from brief hunting expeditions to seasonal hunting-gathering and finally to permanent settlements-has attracted both general interest and substantial scientific debates [3-6].Archaeological studies indicate that humans probably first explored the plateau at the end of the late Pleistocene.They practiced intensive seasonal hunting-gathering from 15 ka BP [6],and permanently settled regions above 3,000 masl after 3.6 ka BP,which was facilitated by the development of an agropastoral economy [3].However, the early part of the human history of the Tibetan Plateau is still poorly documented,due to the lack of well-preserved archaeological sites and reliable dating results (Fig.la).

A review on the spread of prehistoric agriculture from southern China to mainland Southeast Asia

The origins and spread of agriculture was one of the milestones in human history.When and how prehistoric agriculture spread to mainland Southeast Asia is highly concerned,which contributed to the formation of modern Austroasiatic in this region.Previous studies mainly focused on the time and route of rice agriculture’s introduction into Southeast Asia while millet agriculture was not paid proper attention.Here we analyze 31214C dating data yielded from charred seeds of rice(Oryza sativa),foxtail millet(Setaria italica)and broomcorn millet(Panicum miliaceum)from 128 archaeological sites in China and mainland Southeast Asia.The result shows that millet farming was introduced to mainland Southeast Asia in the late third millennium BC and rice farming was in the late second millennium BC.The agriculture of mainland Southeast Asia might originate from three areas,Southwest China,Guangxi-West Guangdong and coastal Fujian.The spread route of ancient agriculture in Southwest China is close to the“Southwest Silk Road”recorded in literature,which implies there was possibly a channel of cultural exchanges on the eastern margin of Tibetan Plateau already in the late Neolithic period,laying the foundation for the Southwest Silk Road later.

Holocene dust storm variations over northern China:transition from a natural forcing to an anthropogenic forcing

Asian dust storms have long been a major environmental concern in China,affecting the lives of about one billion people.However,it is unclear whether the mechanisms responsible for Asian dust storms during the Holocene varied on different timescales,and thus it is unclear whether there was a shift from a natural forcing to an anthropogenic forcing of dust storms.We reconstructed a high-resolution Holocene record of dust storms from the sediments of an undisturbed alpine lake on the Chinese Loess Plateau.We found that Asian dust storm activity generally increased during the Holocene,with the largest fluctuations occurring during the past 2000 years.The increase in dust storm activity was in contrast to the decrease in East Asian winter monsoon(EAWM)intensity during the Holocene,indicating that the EAWM played a limited role in modulating dust storms.By contrast,the increase in dust storms corresponded to a decrease in East Asian summer monsoon(EASM)precipitation.This demonstrates that EASM precipitation was the dominant control of dust storm activity on a millennial timescale,because decreased EASM precipitation expanded the desert area and thus increased the dust storm activity.The increasing intensity of human activity in the region since the Bronze Age resulted in an acceleration of dust storm activity against the background of decreased EASM precipitation.As human disturbance continued to intensify,beginning at least at~2 cal ka BP,increased dust storms were closely linked to increasing human populations in the dust source regions,and there is a strong temporal coherence between increased dust storms and higher EASM precipitation.This was completely different from when natural processes are dominant.During that period,fewer dust storms occurred during periods of a strengthened EASM.Therefore,there was a shift from a natural forcing to an anthropogenic forcing of dust storms on a multi-decadal to centennial timescale,and was a mode in which‘‘human activity overtook the EASM as the dominant control of the Earth surface system”.

The Tibetan Plateau as the engine for Asian environmental change:the Tibetan Plateau Earth system research into a new era

The Tibetan Plateau(TP),as the world’s highest plateau,has almost all the key elements of the entire Earth system,including interconnected lithosphere,atmosphere,cryosphere,biosphere and anthroposphere[1-3].This completeness makes the TP an ideal natural laboratory for studying multispheric interactions within the Earth system,and for cultivating key breakthroughs in geoscience of the 21st century[2,3].

Megadrought and cultural exchange along the proto-silk road

Arid Central Asia(ACA), with its diverse landscapes of high mountains, oases, and deserts, hosted the central routes of the Silk Roads that linked trade centers from East Asia to the eastern Mediterranean.Ecological pockets and ecoclines in ACA are largely determined by local precipitation. However, little research has gone into the effects of hydroclimatic changes on trans-Eurasian cultural exchange. Here,we reconstruct precipitation changes in ACA, covering the mid-late Holocene with a U-Th dated, ~3 a resolution, multi-proxy time series of replicated stalagmites from the southeastern Fergana Valley,Kyrgyzstan. Our data reveal a 640-a megadrought between 5820 and 5180 a BP, which likely impacted cultural development in ACA and impeded the expansion of cultural traits along oasis routes. Instead,it may have diverted the earliest transcontinental exchange along the Eurasian steppe during the 5 th millennium BP. With gradually increasing precipitation after the megadrought, settlement of peoples in the oases and river valleys may have facilitated the opening of the oasis routes, ‘‘prehistoric Silk Roads", of trans-Eurasian exchange. By the 4 th millennium BP, this process may have reshaped cultures across the two continents, laying the foundation for the organized Silk Roads.

2060年中国实现碳中和所面临的挑战:现状与展望

China’s high ambitions to reach peak CO_(2) emissions by 2030 and carbon neutrality by 2060 make carbon mitigation an urgent issue with widespread societal consequences.To develop an achievable roadmap and an effective portfolio of climate policies,it is essential that a clear picture of the magnitude and uncertainty of China’s current carbon balance is available,at both national and regional levels.

The northern boundary of the Asian summer monsoon and division of westerlies and monsoon regimes over the Tibetan Plateau in present-day

Precipitation patterns and their variations over the Tibetan Plateau(TP) are mainly dominated by the Asian summer monsoon, westerlies, and their interactions. The exact extent of the Asian summer monsoon’s influence, however, remains undetermined. Referencing the climatological northern boundary index of the East Asian summer monsoon, we demonstrate that the 300 mm precipitation isoline from May to September can be utilized as an indicator of the northern boundary of the Asian summer monsoon over the TP, allowing for an analysis of the spatial distribution characteristics of the climatological and interannual northern boundary. Our results indicate that the climatological northern boundary of the Asian summer monsoon over the TP lies along the eastern Qilian Mountains-Tanggula Mountains-Qiangtang Plateau-Gangdise Mountains-Western Himalayas during 2001–2020. This position corresponds well with the position of the convergence of westerly(westerlies) and southerly wind(monsoon) in the lower troposphere, representing the interface between dry and wet regions in the rainy season over the TP. There is a significant positive correlation between changes in the zonal/meridional water vapor budget and variations in precipitation to the north/south of the climatological northern boundary, respectively. Additionally, a close relationship exists between the interannual fluctuation range of the northern boundary and the distribution of vegetation across the TP. Compared to the northern boundary of the summer monsoon defined by meteorological criteria, which is established based on 5-day(pentad)mean precipitation(exceeding 4 mm day^(-1)), our climatological northern boundary offers a more objective portrayal of the region that experiences persistent influence from the summer monsoon. These indicate that climatological northern boundary has a clear significance for natural geographical distribution such as the westerlies-monsoon circulation, ecology, and climate. Based on the interannual fluctuation range of the northern boundary, we divided the TP into domains of westerlies, monsoon, and westerliesmonsoon transition. This study could serve as a foundation for further investigation into the interactions between westerlies and monsoon, variations in precipitation patterns and hydrological-ecological systems over the TP.

Discussion of the“warming and wetting”trend and its future variation in the drylands of Northwest China under global warming

Since Shi et al.proposed that the climate in the drylands of Northwest China experienced a significant transition from a“warming and drying”trend to a“warming and wetting”trend in the 1980s,researchers have conducted numerous studies on the variations in precipitation and humidity in the region and even in arid Central Asia.In particular,the process of the“warming and wetting”trend by using obtained measurement data received much attention.However,there remain uncertainties about whether the“warming and wetting”trend has paused and what its future variations may be.In this study,we examined the spatiotemporal variations in temperature,precipitation,the aridity index(AI),vegetation,and runoff during 1950-2019.The results showed that the climate in the drylands of Northwest China and the northern Tibetan Plateau is persistently warming and wetting since the 1980s,with an acceleration since the 1990s.The precipitation/humidity variations in North China,which are mainly influenced by summer monsoon,are generally opposite to those in the drylands of Northwest China.This reverse change is mainly controlled by an anomalous anticyclone over Mongolia,which leads to an anomalous easterly wind,reduced water vapor output,and increased precipitation in the drylands of Northwest China.While it also causes an anomalous descending motion,increased water vapor divergence,and decreased precipitation in North China.Precipitation is the primary controlling factor of humidity,which ultimately forms the spatiotemporal pattern of the“westerlies-dominated climatic regime”of antiphase precipitation/humidity variations between the drylands of Northwest China and monsoonal region of North China.The primary reasons behind the debate of the“warming and wetting”trend in Northwest China were due to the use of different time series lengths,regional ranges,and humidity indices in previous analyses.Since the EC-Earth3 has a good performance for simulating precipitation and humidity in Northwest and North China.By using its simulated results,we found a wetting trend in the drylands of Northwest China under low emission scenarios,but the climate will gradually transition to a“warming and drying”trend as emissions increase.This study suggests that moderate warming can be beneficial for improving the ecological environment in the drylands of Northwest China,while precipitation and humidity in monsoon-dominated North China will persistently increase under scenarios of increased emissions.

Holocene thermal maximum mode versus the continuous warming mode:Problems of data-model comparisons and future research prospects

The Holocene,the most recent interglacial,provides an important time window for evaluating current global warming and predicting future temperature changes.With the development of new temperature proxies and improvements in climate models,significant progress has been made in understanding Holocene temperature changes.However,a major debate persists about whether global temperatures during the Holocene followed a pattern of gradual warming from the end of the Last Glacial Maximum,which culminated in a temperature maximum in the early to middle Holocene,followed by gradual cooling in the late Holocene(the thermal maximum mode);or whether there was a continuous warming trend that continued to the present day(the continuous warming mode).Significant discrepancies exist between different proxy records as well as between proxy records and models,which have resulted in the “Holocene temperature conundrum” that has challenged paleoclimatologists for the past decade.Here,we summarize the progress made to date in the study of Holocene temperature change via proxy reconstructions,climate model simulations,and paleoclimate data assimilation.We emphasize that the current research has limitations in terms of the multiplicity and seasonality of proxy records,the spatial heterogeneity of temperature records,and the incorporation of feedback processes(e.g.,vegetation,cloudradiation feedback) in climate models.These limitations have hindered a comprehensive understanding of the processes and mechanisms of Holocene temperature changes.To solve the “Holocene temperature conundrum”,it is necessary to strengthen theoretical research on climate proxies from the perspective of the underlying processes and mechanisms,elucidate the seasonal response of various temperature proxies,emphasize regional differences in temperature changes,and expand quantitative temperature reconstructions to areas with limited records.However,it is also necessary to improve the simulation performance of complex feedback processes in climate models,reduce simulation errors,and advance the research on data assimilation of Holocene continental temperature records,which may ultimately lead to the optimal integration of paleoclimate records and simulations.

The current and future of terrestrial carbon balance over the Tibetan Plateau

The contemporary carbon balance over the Tibetan Plateau is highly uncertain with a ten-fold difference between various estimates.In a warming world,the potential exists for a large carbon release from its permafrost which could compromise China’s 2060 carbon-neutral goal.Here,we used a satellite-and inventory-based approach,ecosystem models,and atmospheric inversions to estimate that the carbon sink was 33.12–37.84 TgC yr^(–1)during 2000–2015.The carbon sink induced by climate change and increasing CO_(2) levels largely overcompensated for a livestock grazing-induced carbon source of 0.38TgC yr^(-1).By 2060,the carbon sink is projected to increase by 38.3–74.5% under moderate to high emissions scenarios,with the enhanced vegetation carbon uptake outweighing the warming-induced permafrost carbon release.The restoration of degraded grassland could sequestrate an additional 9.06 TgC yr^(-1),leading to a total carbon sink of 57.78–70.52 TgC yr^(-1).We conclude that the Tibetan Plateau’s ecosystems absorbed two-and-a-half times the amount of its cumulative fossil CO_(2) emissions during 2000–2015 and that their carbon sinks will almost double in strength in the future,helping to achieve China’s pledge to become carbon neutral by 2060.

Emergence of ancient cities in relation to geopolitical circumstances and climate change during late Holocene in northeastern Tibetan Plateau, China

The study of the history of human activities in ancient cities has provided valuable evidences for under- standing the evolution of human-land relations during the late Holocene. Numerous ancient cities were discovered through archaeological surveys of the east Qinghai Province, located on the northeastern border of the Tibetan Plateau, China; however, the mystery of when or why these cities were built remains unsolved. As recorded in this paper, we sampled reliable dating materials from 47 ancient cities in the area, determined their ages by radiocarbon dating, and compared the dating results with historical documents and high resolution paleoclimate records to explore the influencing factors for the develop- ment of these ancient cities. The 54 radiocarbon dates indicated that most of these cities were built or repaired during the Han Dynasty （202 BC-AD 220）, Tang Dynasty （AD 618-AD 907）, the Five Dynasties and Ten Kingdoms period （AD 907-AD 960）, the Song dynasty （AD 960-AD 1279）, and the Ming Dynasty （AD 1368-AD 1644）. The radiocarbon dates correspond well with historical records of the area. Our work suggests the ancient cities in east Qinghai Province were likely built primarily for military defense, and may have also have been affected by climate change.