In this study, the NCEP1 (National Centers for Environmental Prediction) daily reanalysis data and GPCC (Global Precipitation Climatology Centre) precipitation reanalysis data from 1961 to 2016 are used to define the spatial range of the northern marginal zone of Asian summer monsoon (ASM). Then, the inter-annual and inter-decadal variations characteristics of precipitation, location and area of the northern marginal zone are analyzed, and the interactions among them are detailedly investigated. Moreover, the physical mechanisms of the summer precipitation anomalies in the ASM marginal zone are explored. The results show that the average position of the ASM northern marginal zone is located in the strip domain which initiates from the central part of the Tibetan Plateau, crosses the Loess Plateau and Northeast China and finally extends to the east coast of Asia. According to the types of underlying surface, regional ecological environment and climate characteristics, the ASM northern marginal zone is divided into three areas: Tibetan Plateau (85°E~105°E), Loess Plateau (105°E~115°E) and Northeast China (115°E~135°E). There is a notable positive correlation between the inter-annual variation of the precipitation in the ASM marginal zone and the location of its southern boundary. In the Tibetan Plateau, there is significant negative correlation between the area of marginal zone and the location of its southern boundary. For the Loess Plateau and Northeast China, there is notable positive correlation between the area and the location of northern boundary of the ASM marginal zone. Moreover, the location, area and precipitation of the three ASM marginal areas have significant inter-annual and inter-decadal variations. The abnormally less precipitation in the ASM marginal zone is related to the wave train of Eurasia teleconnection pattern over middle-high latitudes. During the period with less precipitation in the ASM marginal zone, the convective activity is weak at low-latitude areas. The anomalous convergence at 200 hPa over the equatorial region on the eastern shore of Africa may lead to the weakening of the ASM and the Somali jet. At 200 hPa, the Asian jet stream is also weaker and more northward. At 500 hPa, under the control of anomalous high pressure over North China, the precipitation caused by the ASM mainly concentrates in South China, and the precipitation in the ASM marginal zone in summer is abnormally less. The synoptic situation of 200 hPa and 500 hPa is opposite from that of ASM marginal zone with more precipitation. The abnormally more precipitation is related to the wave train of the Silk Road pattern in middle-high latitudes over Eurasia. The summer monsoon precipitation in East Asia is characterized as "more in the north and less in the south", and the summer precipitation in the ASM marginal zone is more than the normal level.

Due to global warming, dry-wet condition of the Qilian Mountains has experienced significant change in recent decades. Thus, predicting future climate change is critical for studies on the environmental evolution. To explore the climate trends under increasing temperature, we took the millennial-scale Middle Holocene Warm Period and the centennial-scale Medieval Warm Period, as "historical analogues" to compare with undergoing global warming. In this paper, we integrated abundant paleoclimate records (e.g., fluvio-lacustrine deposits, ice cores, pollen, and tree rings) in the Qilian Mountains region and paleoclimatic model simulation of the PMIP3/CMIP5 project to assess the response of dry-wet change during warm periods. Results show that strong East Asian summer monsoon brought a warm and humid climate with more precipitation during the Mid-Holocene warm period (7.2-6.0 ka BP). The Medieval Warm Period (950-1250 AD) and the little ice period show a combination of warm-dry and cold-wet climate. Modern observational data show that the climate of the study region is becoming warm and humid. Modern climates have similarities with historical warm periods at millennial and centennial scales. However, the historical analogues are due to the orbital parameters and insolation. In modern warm period they are caused by greenhouse gases and human activities. Therefore, in order to predict the future dry and wet pattern in the study area accurately, the joint effect of natural factors and human activities should be elucidated.

The Yellow River Basin (YRB) has been facing severe water shortages, hence the monitoring of long-term dynamics of surface water area (SWA) is essential to better understand the spatial and temporal variation of surface water resources and its driving factors. In this study, the spatial and temporal change characteristics of SWA in the YRB were revealed, and then the impacts and relative impact rate of precipitation (Pre), temperature (Temp), leaf area index (LAI), SWA in the previous year (Pre_SWA) and residual factors (e.g. water conservation measures and human water use activities) on SWA were determined in the combination of water detection index, linear slope, multiple linear regression and partial differential decomposition. The results show that: (1) the overall accuracy of classification of surface water bodies is 97%. The increase rate of year-long SWA in the study area from 1986 to 2019 is 49.82 km²/a, of which 83.2% was contributed by the SWA increment from the main river channel area, and the year 2001 is the turning point of SWA trend from decreasing to increasing; the seasonal SWA decreased at a rate of -79.2 km²/a, of which 61.8% was contributed by the SWA decrease in the sub-basin areas. (2) The SWA changes of all major natural lakes are relatively stable, and the only decreasing trend of SWA was observed in the Hongjiannao lake; the SWA of Xiaolangdi and Longyangxia reservoirs changed significantly with an increasing trend among the large reservoirs in the main river channel, and SWA increasing trends can be observed in the 50 sub-basins located in the middle and lower reaches. (3) Precipitation had the least effect on the increasing trend of SWA, and warming caused a decrease of SWA in the middle reaches, but led to an increase of SWA in the source area. The impacts of vegetation greening on the SWA trend in the main channel area and sub-basin areas are 10.12 km²/a and 7.26 km²/a, respectively. Residual factors had a negative reffect on the SWA trend in the sub-basin areas, where the SWA reduction induced by human water use was much greater than the SWA increment induced by small water conservancy projects. However, residual factors had a positive effect on the SWA increase due to the great regulating storage capacity of large reservoirs in the main river channel area.

During the past few years, an increasing number of studies in both China and abroad have highlighted a long-term warming trend during the Holocene. However, this trend challenges the traditional view of a long-term Holocene cooling trend and a "mid-Holocene Megathermal". Comparison of long-term records indicating a rising global sea level, a decreasing area of terrestrial ice-sheets, and increasing radiative forcings of insolation and GHGs (greenhouse gases) leads us to conclude that a long-term Holocene warming trend is more reasonable than the cooling trend. In the original literature documenting a "mid-Holocene Megathermal" and the subsequent late Holocene cooling trend in China, the uncertainties in the supporting evidence are clearly indicated. These uncertainties have been further demonstrated by recent results that the most significant uncertainty arises from the impacts of human activities on sedimentary proxies, especially in the late Holocene when these impacts were greatly intensified. Thus, reconstructions of late Holocene temperature history based on sedimentary proxies are potentially biased by human impacts. Given that the current debate regarding temperature history of the Holocene focuses on the late Holocene, we propose that future emphasis should be placed on the temperature history of the late Holocene. We suggest that more reliable late Holocene temperature records should come from areas and/or sedimentary proxies that are weakly influenced by human activities, which is especially important to studies on the development of Chinese civilization that lasted for over several millennia. Overall, reliable late Holocene temperature records can potentially provide a reliable foundation for improving our understanding of the following themes: (1) the development of Chinese civilization under the background of long-term temperature change; (2) the evolutionary history of "human-land relationship" during the late Holocene; and (3) the climatic and environmental issues associated with global warming.

The Wutou (WT) section (21°32′8.25″N, 108°06′59.9″E), with a thickness of 393 cm storm sediments located in Jiangping, Guangxi Zhuang Autonomous Region, consists of dune sands-lagoon facies-weak pedogenic sedimentary sequences of the Late Holocene. Based on sedimentary characteristics of storm strata in the field investigation, 6 AMS-¹⁴C, OSL dating ages and the analyses of grain size and heavy minerals, the evolution history of storm surges has been reconstructed over the past thousand of years along the coast of the Beibu Gulf in Guangxi. The results show that the storm sediments are characterized as coarse mean grain size and poor sorting, with high maturity of heavy minerals and low stability, which results from quick accumulation caused by the storm surge from the land-facing side of the coastal backside dune sands. Nine storm surge peak periods recorded in the WT section over the past millennia are mainly concentrated within the Little Ice Period after 1400 AD, which are inversely correlated with the trends of SST and ENSO activities in the western Pacific. Some of storm surge peak periods recorded in the WT section and 4 "sea overflow" events from historical documents nearly synchronized with the changes of the sunspot activity. This suggests that the storm surge peak periods revealed by the WT section are probably controlled by the solar activity to a great extent, in addition to the impact of the Western Pacific Warm Pool and ENSO.

The North China Plain is a typical diluvial-alluvial plain with an unstable depositional environment and poor sedimentary continuity. However, the effects of changes in sedimentary phases or hiatuses were not considered in previous studies of the sedimentary record of the North China Plain, which limits our understanding of the environmental and climatic evolution of the region during the historical period. Baiyangdian, the largest freshwater lake in the plain, is a potentially valuable archive of regional paleoenvironmental information since the late Pleistocene. We investigated a sedimentary profile (BG-2019; 38°46'2.55"N, 115°49'0.41"E; 7 m a.s.l) in Gaoyang County, in the southwestern part of Baiyangdian Lake region; the profile is ~6 m long. The results of AMS ¹⁴C and OSL dating indicate that profile BG-2019 has two intervals of lacustrine facies, two intervals of fluvial facies, one interval of swamp facies, one interval of fluvial-lacustrine delta facies, and two intervals of non-deposition or stratigraphic lacunae. The ages of the various facies are as follows. Lacustrine facies: 10270-13710 cal a BP and 4630-5400 cal a BP; swamp facies: 3470-3700 cal a BP; fluvial-lacustrine delta facies: 7130-8000 cal a BP; fluvial facies: 3700-4630 cal a BP and 3230-3470 cal a BP;; intervals of interrupted deposition: 8000-10270 cal a BP and 5400-7130 cal a BP. Therefore, no continuous lacustrine facies exists in the Baiyangdian region since the Lateglacial. Baiyangdian was a small lake during the Lateglacial, but was more extensive during the middle Holocene, although with discontinuous lacustrine facies. During the late Holocene the lake began to shrink under the influence of climate change and human activity. No other than human activity around the modern Baiyangdian Lake was reserved. Pollen analysis shows that the vegetation landscape of the Baiyangdian Basin differed substantially between the Lateglacial and the middle Holocene. During the Lateglacial, the climate was cold and dry, and vegetation dominated by Artemisia, Chenopodioideae, Poaceae and Asteraceae developed in the plain, while the western mountains had a limited forest cover. During the middle Holocene, when the climate was warm and humid, grassland vegetation dominated by Artemisia, Chenopodioideae and Poaceae developed in the plain; Ceratopteris and aquatic plants flourished in and around the lake; and coniferous-broadleaved mixed forest dominated by Pinus and Quercus developed in the western mountains, with an increased forest cover. During the middle-late Holocene, when the climate was relatively mild and dry, grassland vegetation dominated by Artemisia, Chenopodioideae and Poaceae persisted in the plain; and coniferous-broadleaved mixed forest dominated by Pinus developed in the western mountains, with a high forest cover age.

The Tibet Plateau and the Hengduan Mountains are located in the southwest of China, being featured by intricate landforms and deep valleys with large slopes. Due to the impacts of fluvial-induced erosions and intense geologic processes, frequent occurrences of geological disasters such as landslides, collapses and debris flows can be observed and are challenging regional sustainable development. Here we developed a random forest (RF) model to identify the geological disaster points within each sub-region. We found that the accuracies of RF models in sub-regions were all larger than 80% and can reach 91%, which evidenced modelling performance of the developed model in this study in identification of the locations with frequent occurrences of geological disasters. Meanwhile, the locations and/regions with frequent occurrences of geological disasters were found mainly in the southern part of the Hengduan Mountain area, and northeast and south parts of the Tibet Plateau, where 87% of all disaster events ranged from small scale to middle-scale. Specifically, from the view of sub-region, areas with frequent occurrences of geological disaster were 17.5 \times {10}^4km², 17.4 \times {10}^4km² and 27.5 \times {10}^4km², respectively. Due to the spatial heterogeneities of landforms, climatic conditions and disturbance intensities from human activities, major causes of geological disasters (without considering classes of geological disasters) vary from sub-region to sub-region. For sub-region Ⅰ (south part of the Hengduan Mountain area), the main driving factors behind the small-scale and middle-scale geological disasters are impacts from constructions of roads and vibration from transportation (attribution ratio (AT) as 20.2%). Besides, main driving factors behind the small-scale and middle-scale geological disasters for both sub-regions Ⅱ~Ⅲwere impacts from vegetation coverages on slope stabilities, whose ATs are 23.6% and 27.3% respectively. Besides, the second most important causes behind small-scale and middle-scale geological disasters for sub-regions Ⅱ~Ⅲ were impacts from constructions of road and transportation (AT as 15.7%) and impacts from river erosions on slope stabilities (AT as 17%) respectively.