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Drought is a major natural disaster that has long-lasting effects on economic and social activities in northern China and has regional distinctions in duration, severity, and spatial extent. In this study, tree-ring chronologies and historical archives in the Yellow River Basin and its surrounding areas were collected to investigate the dynamic process of the two extreme drought events for the past ~200 years. Here we directly employ the tree index instead of the climate indicator reconstruction to partly overcome the drought information loss during tree-ring based reconstruction. Identified drought history is improved significantly relative to the single indicator reconstruction and drought events are highly consistent with historical recorded ones. Two prominent drought events in the modern Chinese history were analyzed, namely the Ding-Wu Great Famine (1876-1879) and the extreme drought in northern China during the late-1920s. Unexpectedly, the most prestigious Ding-Wu Great Famine is lower than the extreme drought in the late-1920s in terms of drought duration, spatial extent and intensity. Our research further reveals that the drought events recorded in the historical records could be very different from actual events due to the influence of political and other factors. The analysis of spatial dynamics indicates that the potential mechanisms of the two drought events are also different. This is confirmed by research based on reanalysis data that the Ding-Wu Great Famine was caused by a typical strong ENSO event, while the mechanism of the extreme drought in the late-1920s was more complicated.

Tree growth trends can affect the interpretation of the response of tree-ring proxies (especially tree-ring width) to climate in the low-frequency band, which in turn may limit quantitative understanding of centennial-scale climate variability. As such, it is difficult to determine if long-term trends in tree-ring measurements are caused by age-dependent growth effects or climate. Here, a trend similarity ranking method is proposed to define the range of tree growth effects on tree-ring width chronologies. This method quantifies the inner and outer boundaries of the tree growth effect following two extreme standardization methods: curve fitting standardization and regional curve standardization. The trend similarity ranking method classifies and detrends tree-ring measurements according to the ranking similarity between the regional growth curve and their long-term trends through curve fitting. This standardization process mainly affects the secular trend in tree-ring chronologies, and has no effect on their inter-annual to multi-decadal variations. Applications of this technique to the Yamal and Torneträsk tree-ring width datasets and the maximum latewood density dataset from northern Scandinavia reveals that multi-centennial and millennial-scale temperature variations in the three regions provide substantial positive contributions to the linear warming trends in the instrumental period, and that the summer warming rate during the 20th century is not unprecedented over the past two millennia in any of the three regions.

This study reports the earlywood and latewood δ18O time series from two hemlock sites located to the east (EQ) and west (WQ) of Mt. Qomolangma (Everest) in the Himalaya. The latewood δ18O series from both sites were highly consistent, whereas the earlywood δ18O values for the two sites show variations over the investigation period. Climate response analysis revealed that the dominant control on latewood δ18O values at both sites was the precipitation amounts of the middle/peak periods of upstream Indian Summer Monsoon (ISM). However, for EQ- and WQ-Earlywood, the main controls were precipitation amounts during the early and middle phases of the upstream ISM, respectively. The upstream amount effect could have accounted for earlywood and latewood δ18O variance. Combined with moisture transport models, we found that source water incorporated into latewood at both sites was derived mainly from the Bay of Bengal and Arabian Sea during middle/peak ISM precipitation. However, during the early ISM, the high ridges of Mt. Qomolangma may block most of the moisture that originates from the Bay of Bengal, which results in a stronger signal of early ISM being recorded in EQ-Earlywood δ18O. The influence of the ISM on WQ-Earlywood is delayed until the middle ISM.

Mass movements in China typically encompass landslides, rockfalls, and debris flows, and these processes affect almost 70% of all mountain areas of China. An improved understanding of geomorphic process dynamics and their drivers and process histories are important prerequisites for a proper assessment and a sustainable management of mountain hazards. Tree rings have on varied occasions proven to be a reliable tool for the acquisition of data on past mountain hazards. Here we present the first reconstruction of past landslide activity on a slope in the Qilian Mountains, northeast Tibetan Plateau, China. To this end, a total of 543 Qilian juniper (Sabina przewalskii Kom.) samples were selected from 239 trees growing on or next to a complex landslide body, with the aim to reconstruct past landslide histories at the site. The dataset of disturbed trees was complemented with 174 increment cores from 84 reference Qilian juniper trees growing on three adjacent, yet undisturbed sites. Based on the dating of the samples and the interpretation of growth disturbances (GD) in the tree-ring series of affected trees, we provide the first reconstruction of past landslides as retrieved from a dendrogeomorphic record covering more than a millennium (956–2011 CE). Results show that the first detectable GD occurred as early as in 1042 CE, followed by seven major landslide reccurrences in 1703, 1816, 1848, 1863, 1913, 1970, and 1982. Comparison between our landslide record and a dendroclimatic precipitation reconstruction points to the crucial role of major, longer-term wet precipitation anomalies on landslide occurrence.

The Aksu area is located in western Xinjiang, China, where an oasis is the main space for human production and life in this region. The stability of the oasis is crucial for societal and economic development and can be severely impacted by continued drought. The Palmer Drought Severity Index (PDSI), a widely applied index for dryness, has been reconstructed in many areas by tree rings. Here we develop a new regional long tree-ring-width chronology of Schrenk’s spruce (Picea schrenkiana Fisch. et Mey.) from the Aksu area. Based on the regional PDSI from the previous September to current March (PDSIp9–c3), regional drought variability is reconstructed in the past 548 years (1466–2013 CE). The regional PDSI reconstruction captures distinct wet and dry periods and also some low-frequency climate signals. A decadal analysis reveals 12 wet and 12 dry periods in the past 548 years, of which 1514–1560 CE was the longest dry period. The prominent mega-drought during the mid-sixteenth century is particularly pronounced. The PDSI in the Aksu area records a notable sudden onset and long period of wet conditions from the 1980s until the present day. Mechanism analysis indicates that the regional drought has been mainly affected by the North Atlantic Oscillation (NAO) over the last centuries through an anti-phase relationship.

The Tibetan Plateau and its surrounding mountains exhibit the largest concentration of glaciers at lower latitudes on earth, providing source water for the large river systems in Asia. However, glacier observations in this region are short and scarce and hence limit a better understanding of glacier behaviors under a warming climate and thereto coupled processes. The purpose of this research is to investigate the potential and the uncertainty for using pioneering trees on glacial deposits/glacier forefields as a proxy record for past glacier fluctuations in the Himalaya-Nyanqentanggula-Hengduan (H2N) area. It was found that Hippophae tibetana spent 4 years to colonize the glacier forefields at Hailuogou glacier and Pinus wallichiana germinated 11 years after glacier retreating at Gangapuna and Raikot glaciers. At deposit sites of glacier avalanche and glacial lake outburst, it took 8 years for Larix griffithii to germinate after the historical events. As shown by bootstrap resampling, the precision of the sampled maximum tree age could reach 2–14 years, which is related to the sample size to ensure the possibility of obtaining the eldest trees. However, if using the traditional sampling method at 100-cm height, errors of tree age estimation may reach up to ±20 years due to uncertainties of pith offset estimation and height-age calibration. If samples are collected with pith from ≤20 cm tree height, an error of

Volcanic eruptions have a significant impact on global temperature; their consequences are of particular interest in regions that are especially sensitive to climate change, like the Tibetan Plateau. In this study, we develop a temperature-sensitive tree-ring width standard chronology covering the period 1348–2014 AD using Qilian juniper (Sabina przewalskii Kom.) samples collected from Animaqin Mountain on the Tibetan Plateau. We reconstruct the annual (prior August to current July) mean minimum temperature (Tmin) since 1380 AD and show that our reconstruction explains 58 % of the variance during the 1960–2014 calibration period. Our results demonstrate in 77.8 % of cases in which a volcanic eruption with a volcanic explosivity index of 5 or greater occurs, temperature decreases in the year of or the year following the eruption. The results of the Superposed Epoch Analysis also indicate that there is a high probability that the Tmin decreases within 2 years of a large volcanic eruption, especially when such eruptions occur in low latitudes.

Inter-annual variations in precipitation play important roles in management of forest ecosystems and agricultural production in Northeast China. This study presents a 270-year precipitation reconstruction of winter to early growing season for the central Lesser Khingan Mountains, Northeast China based on tree-ring width data from 99 tree-ring cores of Pinus koraiensis Sieb. et Zucc. from two sampling sites near Yichun. The reconstruction explained 43.9 % of the variance in precipitation from the previous October to current June during the calibration period 1956–2017. At the decadal scale, we identified four dry periods that occurred during AD 1748–1759, 1774–1786, 1881–1886 and 1918–1924, and four wet periods occurring during AD 1790–1795, 1818–1824, 1852–1859 and 2008–2017, and the period AD 2008–2017 was the wettest in the past 270 years. Power spectral analysis and wavelet analysis revealed cyclic patterns on the inter-annual (2–3 years) and inter-decadal (~11 and ~32–60 years) timescales in the reconstructed series, which may be associated with the large-scale circulation patterns such as the Arctic Oscillation and North Atlantic Oscillation through their impacts on the Asian polar vortex intensity, as well as the solar activity.

Elevated CO2 level in the atmosphere is expected to improve the tree growth rates and intrinsic water-use efficiency (iWUE). Although current results inferring from tree rings found the tree growth decline in water-limited area, it is still unclear whether spruce trees in humid southwestern China benefit from the increasing CO2. In this study, tree-ring width data were used to investigate the tree radial growth rate of Chuanxi spruce (Picea likiangensis var. balfouriana). Moreover, combining with the tree-ring carbon isotope date, we analyzed the physiological responses of Chuanxi spruce to rising CO2 concentrations in the atmosphere (Ca) associated with climatic change in southwestern China. From 1851 to 2009, iWUE of Chuanxi spruce rose by approximately 30.4%, and the ratio of atmospheric CO2 to leaf intercellular CO2 concentration (Ci/Ca) showed no significant trend in the study area. The result suggested that Chuanxi spruce used an active response strategy when Ca was significantly increased. iWUE showed a significant increasing trend in parallel with tree radial growth, indicating that the increasing iWUE resulted in an increase in radial growth. These results suggest that spruce forests in southwestern China have not shown declining trends under increasing Ca and climate change scenarios, in contrast to trees growing in water-limited areas. Therefore, spruce forests benefit from the increasing CO2 in the atmosphere in the humid areas of southwestern China.

Inter-annual variations of precipitation play important roles in forest management and agricultural production. This study presents a 270-year precipitation reconstruction of winter to early growing season for the central Lesser Khingan Mountains, Northeast China based on tree-ring width data of 99 tree-ring cores of Korean pine from two sampling sites near Yichun city. The reconstruction explained 46% of the variance in precipitation from the previous October to current June during the calibration period CE 1959–2017. At decadal scale, we identified four dry periods that occurred during CE 1748–1759, 1774–1786, 1881–1886 and 1918–1924, and four wet periods occurring during CE 1790–1795, 1818–1824, 1852–1859 and 2008–2017, and the period CE 2008–2017 was the wettest in the past 270 years. Power spectral analysis and wavelet analysis revealed cyclic patterns on the inter-annual (2–3 years) and inter-decadal (~11 and ~30–60 years) timescales in the reconstructed series. In addition, the Asian polar vortex has an important effect on the precipitation in our study area.

Production scheduling under time-of-use electricity tariffs has become an efficient way for energy-intensive industries to decrease energy costs. However, when production tasks are over-concentrated in one scheduling cycle, the effectiveness of time-of-use electricity tariffs is no longer significant. This makes the introduction of self-generation power plant appealing for energy-intensive industries. This paper addresses an integrated scheduling problem from an iron-steel plant equipped with self-generation equipment under time-of-use electricity tariffs. In this problem, time-of-use electricity tariffs, the self-generation cost, and the on-grid electrovalence influence the total electricity cost simultaneously. A multi-objective mathematical model with energy-awareness is developed to optimize the production schedules and electricity cost jointly. An improved SPEA2 based on the relationship propagation chain is tailored for the problem, including scheduling solution encoding, crossover and mutation. A real-life case study from a Chinese iron-steel plant equipped with self-generation equipment demonstrates that the proposed methods can provide a high-quality scheduling scheme and the total electricity cost can be significantly reduced.

This study presents a 304-year mean July-October maximum temperature reconstruction for the southeastern Tibetan Plateau based on both tree-ring width and maximum latewood density data. The reconstruction explained 58% of the variance in July-October maximum temperature during the calibration period (1958-2005). On the decadal scale, we identified two prominent cold periods during AD 1801-1833 and 1961-2003 and two prominent warm periods during AD 1730-1800 and 1928-1960, which are consistent with other reconstructions from the nearby region. Based on the reconstructed temperature series and volcanic eruption chronology, we found that most extreme cold years were in good agreement with major volcanic eruptions, such as 1816 after the Tambora eruption in 1815. Also, clusters of volcanic eruptions probably made the 1810s the coldest decade in the past 300 years. Our results indicated that fingerprints of major volcanic eruptions can be found in the reconstructed temperature records, while the responses of regional climate to these eruption events varied in space and time in the southeastern Tibetan Plateau.

In this study we reconstructed the moisture condition of the eastern Qaidam Basin of the northeastern Tibetan Plateau based on a 3585-year tree ring chronology. The growth environment of Qilian juniper ( Sabina przewalskii Kom.) on the mountains in the eastern Qaidam Basin was first determined by comparing precipitation and temperature estimates from two spatial datasets (PRISM and World Climate). Moisture balance was calculated as the sum of simulated moisture deficit (negative) and surplus using a modified Thornthwaite water balance model, and used as a proxy of biological drought conditions. Using data during 1956–2005, we established the transfer function to reconstruct a 2847-year series of January–June moisture balance (843 BCE–2004 CE). With an adjusted R 2 value of 0.654 of the transfer function and strong performance in validation, the reconstructed January–June moisture balance can be considered an excellent indicator of biological drought conditions for the study region. The reconstructed series showed strong correlations with reconstructed PDSI in the monsoon Asian region, representing a region of 10° latitudes by 20° longitudes. Using the reconstructed series, we identified centennial-scale dry periods since 843 BCE: 381–277 BCE, 425–520 CE, 1108–1212 CE, 1428–1516 CE, and 1634–1743 CE. Additionally it had statistically significant negative correlations with a monsoon intensity proxy based on oxygen stable isotope from southwestern China (Dongge Cave). Further analyses identified significant relationships with solar activity, especially during the last 700 years. We confirmed the ~ 200-year cyclic pattern in the reconstructed moisture balance series, which matched the known 210-year de Vries solar cycle and peaked during the Little Ice Age. However, the cyclic patterns of the reconstructed moisture balance series and solar activity were decoupled for the period prior to approx. 1300 CE.

Understanding historical hydroclimate change during the last millennium is of fundamental importance for forecasting and evaluating the regional hydrologic cycle and water security under global warming. Here we compared observations of tree‐ring stable isotope ratios (δ13C and δ18O), tree‐ring widths, lake sediments estimates of regional hydroclimate, and glacier advance and retreat for northeastern Qinghai‐Tibetan Plateau, China. The hydroclimate dynamics in our composite isotope record is similar to that derived from the juniper tree‐ring widths throughout the last millennium until the latter half of the twentieth century, after which they diverged with the tree‐ring widths indicating an unprecedented wet period while the isotopic results, sediment proxies, and glaciers demonstrated a drying pattern. Rising atmospheric CO2 promoted increases in canopy‐scale intrinsic water‐use efficiency and growth, causing tree‐ring widths to overestimate the regional hydroclimate signal in the growth record. Thus, our study suggests that CO2 fertilization over the last century may confound hydroclimate reconstructions inferred from juniper tree‐ring width at northeastern Qinghai‐Tibetan Plateau, which may cause overestimates of water resources. Correction for CO2‐induced changes in tree‐ring widths may be necessary to accurately utilize tree rings for paleoclimate reconstructions.

A 2665-year ring-width chronology was developed based on Qilian juniper from the upper treeline of the Animaqin Mountains on the eastern Tibetan Plateau. Correlation analysis results showed that the chronology was significantly negatively correlated with April–June maximum temperature at nearby meteorological stations, indicating that maximum temperature is the factor that limits tree growth in this area. Accordingly, we reconstructed the average April–June maximum temperature variations since 261 BC. Our regression model explained 37.9% of the total variance for the whole calibration period of 1960–2012. Our reconstruction revealed that the maximum temperature started to increase from approximately 1750 without a rapid warming trend, and the warmest period was from AD 890 to 947, as opposed to the recent period, whereas the period from AD 351–483 was the coldest. Significant periods in the wavelet power spectrum were approximately 2–8 years, 20–30 years, 30–60 years, and 60–130 years, as well as some long-term periods (more than 200 years). Comparisons with other temperature series from neighboring regions and the Northern Hemisphere as a whole support the validity of our reconstruction and suggest that it provides a representation of the temperature change for the Animaqin area, although asymmetric variation patterns in minimum and maximum temperatures were found.

Anatomical characteristics have been proven useful for extracting climatic signals. To examine the climatic signals recorded by tree-ring cell features in the Changbai Mountains, we measured cell number and cell lumen diameter, in addition to ring widths, of Korean pine (Pinus koraiensis) tree rings at sites of varied elevation, and we developed chronologies of cell number (CN), mean lumen diameter (MLD), maximum lumen diameter (MAXLD) and tree-ring width (TRW). The chronologies were correlated with climatic factors monthly mean temperature and the sum of precipitation. As shown by our analysis, the cell parameter chronologies were suitable for dendroclimatology studies. CN and TRW shared relatively similar climatic signals which differed from MLD and MAXLD, and growth-climate relationships were elevation-dependent, as shown by the following findings: (1) at each elevation, MLD and MAXLD recorded different monthly climatic signals from those recorded by TRW for the same climatic factors; and (2) MLD and MAXLD recorded climatic factors that were absent from TRW at lower and middle elevations. Cell lumen diameter proved to be an effective archive for improving the climate reconstruction for this study area.

Key message Both temperature and precipitation are strong factors of radial tree growth at all elevations in the semi-arid study area, except at the upper treeline where temperature becomes the major controlling factor.

The net primary productivity (NPP) of Pinus koraiensis , estimated from tree-ring widths, has a significant correlation with the minimum temperature in April and the summer precipitation over the past 50 years. This study investigated the relationship between climate and Pinus koraiensis net primary productivity (NPP) (estimated using tree-ring widths) and the effect of climate on NPP in the Changbai Mountains. Three typical areas of Pinus koraiensis and a broad-leaved mixed forest were investigated and sampled. NPP was estimated using biomass equations and the annual diameter at breast height, calculated from tree-ring widths. A stepwise regression was used for the quantitative analysis of the response of NPP to climate variation, whereas correlation and response analyses were used to illustrate the relationship between the climatic variables and NPP. The results showed that between 1960 and 2012, the biomass of sampled Pinus koraiensis in the Changbai Mountains almost doubled, from 107.70 to 205.29 t ha−1. The NPP of Pinus koraiensis varied steadily within a confined range over the past 52 years, with an average of 1.88 t ha−1 year−1. In this study, it was deduced that NPP was simultaneously affected by temperature and precipitation. The minimum temperature in April and the precipitation in June and July, which most affected the changes in NPP, could explain 28.4 % of the NPP variance. The extreme values of these principal climatic controls corresponded well with extreme NPP values. However, an increase in NPP caused by recent warming prior to the growing season might have been offset by a decrease in summer precipitation. Furthermore, the effect of temperature change on NPP was complex. An increase in monthly low temperatures induced by warming acted to increase NPP, while the monthly high temperatures during the growing season had a negative impact on NPP for the drought.

There are differing views regarding the climatic factors that limit radial growth of Qilian juniper (Juniperus przewalskii Kom.) at the upper treelines on the northeastern Tibetan Plateau. In this study, trees from an upper treeline site in the Anyemaqen Mountains of the northeastern Tibetan Plateau were selected to present new evidence that low temperature limits the radial growth of Qilian juniper. Using a signal-free regional curve standardization (SF-RCS) method, a ring-width chronology for Qilian juniper was developed extending from AD 1082 to 2010. The results of correlation analysis between tree-ring index and instrumental climatic variables showed that both winter (December in the previous year and January in the current year) and summer (July and August in the current year) temperatures were significantly and positively correlated with the tree-ring index. Precipitation in June was also significantly and positively correlated with the tree-ring index, but was not as important as low temperature in controlling tree growth. To test the key limiting climatic factor for tree radial growth at different altitudes, an indicator termed the “relative distance to upper treeline” (RDUT) was developed to quantify the representativeness of collected samples for the forest’s upper treeline. The RDUT showed that the upper 20% of the forest belt may be an important boundary in terms of capturing the temperature signal from tree-ring width at the upper treelines on the northeastern Tibetan Plateau. Our findings enhance the existing understanding that temperature is the limiting factor at upper treelines on the northeastern Tibetan Plateau, and will be useful in the reconstruction of past temperature in future studies.

Tree growth in the mid-latitudes of the northern hemisphere reveals significant inter-annual variation in carbon sequestration, and the variations have been widely attributed to climate change, especially to the recent rapid warming and increasing drought stress. However, the response of natural trees under the different regions that exist in the northeastern Qinghai-Tibetan Plateau remains unclear. Here, we use nine Qilian juniper (Sabina przewalskii) tree-ring width and basal area increment (BAI) chronologies from the middle of the Qilian Mountains and the northeastern Qaidam Basin to quantify tree growth trends and their response to the recent rapid warming. The trees, growing at high and low elevations, exhibited a consistent pattern of inter-annual variations, with increasing synchronicity in their trends since 1950. Responses to several climate factors indicate that increasing temperature accelerated tree growth in the middle of the Qilian Mountains, but restricted tree growth in the northeastern Qaidam Basin. Moving-window correlation analyses demonstrate a clearly contrasting response to the temperature variations. Our findings suggest that growth of Qilian juniper in the middle of the Qilian Mountains will increase steadily in the future rapid warming, but may remain constant or even decrease in the northeastern Qaidam Basin. These contrasting responses to temperatures provide valuable information on forest dynamics in the critical mid-latitude regions that should be incorporated into predictions of future forest carbon cycling under global warming.

A 1343-year tree-ring chronology was developed from Qilian junipers in the central Qilian Mountains of the northeastern Tibetan Plateau (TP), China. The climatic implications of this chronology were investigated using simple correlation, partial correlation and response function analyses. The chronology was significantly positively correlated with temperature variables prior to and during the growing season, especially with monthly minimum temperature. Minimum temperature anomalies from January to August since AD 670 were then reconstructed based on the tree-ring chronology. The reconstruction explained 58% of the variance in the instrumental temperature records during the calibration period (1960–2012) and captured the variation patterns in minimum temperature at the annual to centennial timescales over the past millennium. The most recent 50 years were the warmest period, while 1690–1880 was the coldest period since AD 670. Comparisons with other temperature series from neighbouring regions and for the Northern Hemisphere as a whole supported the validity of our reconstruction and suggested that it provided a good regional representation of temperature change in the northeastern Tibetan Plateau. The results of wavelet analysis showed the occurrence of significant quasi-periodic patterns at a number of recurring periods (2–4, 40–50, and 90–170 years), which were consistent with those associated with El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and solar activity. The comparison between the reconstructed temperature and the index of tropical volcanic radiative forcing indicated that some cold events recorded by tree rings may be due to the impact of tropical volcanic eruptions.

Barrier coverage is known as one of the most important applications in wireless sensor networks. Most existing studies adopted the Boolean Sensing Model (BSM) which assumes that sensor can detect the object falling in the sensing range of that sensor. Another sensing model, called Elfes Sensing Model (ESM), which assumes that the probability of sensing is a probabilistic value depending on the distance between sensor and object. The ESM model is more practical than BSM model since it considers the interference and other environmental conditions. This paper considers the ESM and proposes a distributed mechanism, called BSQ (Barrier coverage for guaranteeing Surveillance Quality), for constructing a barrier coverage. The proposed BSQ aims to maximize the weakest sensing quality of barrier boundary while satisfying the minimum numbers of sensors. Experimental study reveals that the proposed BSQ outperforms existing related schemes in terms of surveillance quality and hardware cost.

Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python., PAGES, a core project of Future Earth, is supported by the U.S. and Swiss National Science Foundations. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Some of this work was conducted as part of the North America 2k Working Group supported by the John Wesley Powell Center for Analysis and Synthesis, funded by the U.S. Geological Survey. B. Bauer, W. Gross, and E. Gille (NOAA National Centers for Environmental Information) are gratefully acknowledged for helping assemble the data citations and creating the NCEI versions of the PAGES 2k data records. We thank all the investigators whose commitment to data sharing enables the open science ethos embodied by this project.

Three tree-ring STD chronologies of Abies faxoniana were developed from Songpan region Sichuan Province, and a regional chronology(RC) was established based on the three STD chronologies. The calculation shows that the tree-ring width was significantly correlated with temperature, and the RC had the highest correlation( r =0.576, P R adj2=32%, N =59, F =28.33). In the past 310 years, there were 8 warm periods and 7 cool periods. According to analysis of temporal and spatial correlation, it indicated that the reconstructed series with good spatial and temporal representation. Our reconstruction was validated by other tree-ring based temperature reconstructions from the surrounding area, glacier advances and retreats, and the documented climate disaster events. MTM analysis shows that there exist periods of 2-3 a, 26 a, quasi-33 a and quasi-40 a cycles.

This study analysed tree-ring stable carbon isotope composition (δ13C) of Pinus tabulaeformis Carr. and Pinus taiwanensis Hayata, from a subtropical forest located in central China for the last 130 years, to obtain the long-term trends of δ13C, carbon isotope discrimination by plants (Δ), leaf internal carbon dioxide (CO2) concentration (c i ) and intrinsic water-use efficiency (iWUE) in response to elevated atmospheric CO2 concentration (c a ) and climate change and explore how environmental changes affected long-term tree physiological responses and growth. Tree-ring cores were taken in Dabie Mountains, the border of Hubei, Henan and Anhui Provinces of China. δ13C was undertaken at every 3-year interval, and Δ, c i , iWUE and basal area increment (BAI) were determined. Regression analysis was used to quantify the trends in climate and the relationships of c i , iWUE and BAI with elevated c a and climate. Partial correlation analysis was used to distinguish the effects of c a and climate on c i and iWUE. δ13C of P. tabulaeformis and P. taiwanensis decreased in the past 130 years, but Δ had no obvious change over time for the two tree species. Both c i and iWUE increased significantly with the calendar year. BAI of P. tabulaeformis continuously increased during 1897–1993, but decreased slightly in the recent 20 years. However, BAI of P. taiwanensis did not present obvious change in the period 1882–2010. The c i and iWUE of P. tabulaeformis and P. taiwanensis also increased linearly with elevated c a in the past 130 years and with mean annual temperature during 1960–2007. Partial correlation analysis showed that elevated c a , not temperature, induced the changes in c a and iWUE. BAI of P. tabulaeformis since 1897 and that of P. taiwanensis during 1975–2010 responded quadratically to elevated c a . Warming-deduced drought in the study area in the recent 30 years resulted in increases in iWUE and decreases in BAI. This study showed that while iWUE increased in the past 130 years, tree growth of two subtropical tree species in central China responded to rising c a non-linearly. Negative effects of some factors on tree growth, such as climate change (particularly warming-induced drought), nutrient limitation and physiological long-term acclimation to elevated c a , have overridden the CO2 fertilization effects in the past 30 years.

We use principal component regression and partial least squares regression to separately reconstruct a composite series of temperature variations in China, and associated uncertainties, at a decadal resolution over the past 2000 yr. The reconstruction is developed using proxy temperature data with relatively high confidence levels from five regions across China, and using a temperature series from observations by the Chinese Meteorological Administration, covering the period from 1871 to 2000. Relative to the 1851–1950 climatology, our two reconstructions show four warm intervals during AD 1–AD 200, AD 551–AD 760, AD 951–AD 1320, and after AD 1921, and four cold intervals during AD 201–AD 350, AD 441–AD 530, AD 781–AD 950, and AD 1321–AD 1920. The temperatures during AD 981–AD 1100 and AD 1201–AD 1270 are comparable to those of the Present Warm Period, but have an uncertainty of ±0.28 °C to ±0.42 °C at the 95% confidence interval. Temperature variations over China are typically in phase with those of the Northern Hemisphere (NH) after 1000, a period which covers the Medieval Climate Anomaly, the Little Ice Age, and the Present Warm Period. In contrast, a warm period in China during AD 541–AD 740 is not obviously seen in the NH.

Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period AD 1971?2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years. Fil: Ahmed, Moinuddin. Federal Urdu University of Arts, Science and Technology. Department of Botany; Pakistán Fil: Anchukaitis, Kevin J.. Columbia University. Lamont Doherty Earth Observatory; Estados Unidos. Woods Hole Oceanographic Institution; Estados Unidos Fil: Asrat, Asfawossen . Addis Ababa University. School of Earth Sciences; Etiopía Fil: Borgaonkar, Hemant P.. Indian Institute of Tropical Meteorology; India Fil: Braida, Martina . University of Trieste. Dipartimento di Matematica e Geoscienze; Italia Fil: Buckley, Brendan M. . Columbia University. Lamont Doherty Earth Observatory; Estados Unidos Fil: Ulf Büntgen. Swiss Federal Research Institute WSL; Suiza Fil: Chase, Brian M.. Université Montpellier. Département Paléoenvironnements et Paléoclimats (PAL); Francia. University of Bergen. Department of Archaeology, History, Cultural Studies and Religion; Noruega Fil: Christie, Duncan A. . Universidad Austral de Chile. Laboratorio de Dendrocronología y Cambio Global; Chile. Universidad de Chile. Center for Climate and Resilience Research; Chile Fil: Cook, Edward R.. Columbia University. Lamont Doherty Earth Observatory; Argentina Fil: Curran, Mark A. J.. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Diaz, Henry F. . National Oceanic and Atmospheric Administration. Cooperative Institute for Research in Environmental Sciences, ; Estados Unidos Fil: Esper, Jan. Johannes Gutenberg University. Department of Geography,; Alemania Fil: Fan, Ze-Xin . Chinese Academy of Sciences. Xishuangbanna Tropical Botanical Garden ; China Fil: Gaire, Narayan P. . Nepal Academy of Science and Technology. Faculty of Science,; Nepal Fil: Ge, Quansheng. Chinese Academy of Sciences. Institute of Geographical Sciences and Natural Resources Research, ; China Fil: Gergis, Joëlle. University of Melbourne. School of Earth Sciences; Australia Fil: González-Rouco, J Fidel. Universidad Complutense de Madrid. Departamento Astrofísica y CC de la Atmósfera; España Fil: Goosse, Hugues. Université Catholique de Louvain. LemaitreCenter for Earth and Climate Research, Earth and Life Institute; Bélgica Fil: Grab, Stefan W. . University of the Witwatersrand. School of Geography,Archaeology and Environmental Studies; Sudáfrica Fil: Graham, Nicholas. Hydrologic Research Center; Estados Unidos Fil: Graham, Rochelle . Hydrologic Research Center; Estados Unidos Fil: Grosjean, Martin . University of Bern. Oeschger Centre for Climate Change Research & Institute of Geography; Suiza Fil: Hanhijärvi, Sami T.. University of Helsinki. Department of Environmental Sciences; Finlandia Fil: Kaufman, Darrell S.. Northern Arizona University. School of Earth Sciences and Environmental Sustainability; Estados Unidos Fil: Kiefer, Thorsten . International Project Office, Past Global Changes (PAGES); Suiza Fil: Kimura, Katsuhiko. Fukushima University. Department of Symbiotic System Science; Japón Fil: Korhola, Atte A.. University of Helsinki. Department of Environmental Sciences; Finlandia Fil: Krusic, Paul J.. Stockholm University. Department of Physical Geography and Quaternary Geology; Suecia Fil: Lara, Antonio. Universidad Austral de Chile. Laboratorio de Dendrocronología y Cambio Global; Chile. Universidad de Chile. Center for Climate and Resilience Research; Chile Fil: Lézine, Anne-Marie. Université Pierre et Marie Curie. Laboratoire d’Océanographie et du Climat: Expérimentations et Approches Numériques (LOCEAN); Francia Fil: Ljungqvist, Fredrik C.. Stockholm University. Department of History, ; Suecia Fil: Lorrey, Andrew M.. National Institute of Water and Atmospheric Research Ltd., National Climate Centre Auckland; Nueva Zelanda Fil: Luterbacher, Jürg. Justus Liebig University. Department of Geography, Climatology, Climate Dynamics and Climate Change; Alemania Fil: Masson-Delmotte, Valérie . Laboratoire des Science du Climat et de l’Environnement, Gif-sur-Yvette; Francia Fil: McCarroll, Danny. Swansea University. Department of Geography; Reino Unido Fil: McConnell, Joseph R.. Nevada System of Higher Education. Desert Research Institute; Estados Unidos Fil: McKay, Nicholas P.. Northern Arizona University. School of Earth Sciences and Environmental Sustainability; Estados Unidos Fil: Morales, Mariano Santos. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Moy, Andrew D.. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Mulvaney, Robert. British Antarctic Survey; Reino Unido Fil: Mundo, Ignacio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Nakatsuka, Takeshi. Nagoya University. Department of Earth and Environmental Sciences; Japón Fil: Nash, David J.. University of the Witwatersrand. School of Geography,Archaeology and Environmental Studies; Sudáfrica. University of Brighton. School of Environment and Technology; Reino Unido Fil: Neukom, Raphael . Swiss Federal Research Institute WSL; Suiza Fil: Nicholson, Sharon E.. Florida State University. Department of Earth, Ocean and Atmospheric Sciences, ; Estados Unidos Fil: Oerter, Hans. Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. Department of Glaciology; Alemania Fil: Palmer, Jonathan G.. University of Exeter. College of Life and Environmental Sciences; Reino Unido. University of New South Wales. Climate Change Research Centre; Australia Fil: Phipps, Steven J.. University of New South Wales. Climate Change Research Centre; Australia. University of New South Wales. ARC Centre of Excellence for Climate System Science; Australia Fil: Prieto, Maria del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Rivera, Andres. Centro de Estudios Cientificos; Chile Fil: Sano, Masaki. Nagoya University. Department of Earth and Environmental Sciences; Japón Fil: Severi, Mirko. University of Florence. Department of Chemistry ‘Ugo Schiff’; Italia Fil: Shanahan, Timothy M.. University of Texas at Austin. Jackson School of Geosciences; Estados Unidos Fil: Shao, Xuemei. Chinese Academy of Sciences. Institute of Geographical Sciences and Natural Resources Research; China Fil: Shi, Feng. Chinese Academy of Sciences. LASG, Institute of Atmospheric Physics, ; China Fil: Sigl, Michael . Nevada System of Higher Education. Desert Research Institute,; Estados Unidos Fil: Smerdon, Jason E.. Columbia University. Lamont Doherty Earth Observatory; Estados Unidos Fil: Solomina, Olga N. . Russian Academy of Sciences. Institute of Geography; Rusia Fil: Steig, Eric J.. University of Washington. Department of Earth and Space Sciences; Estados Unidos Fil: Stenni, Barbara. University of Trieste. Dipartimento di Matematica e Geoscienze; Italia Fil: Thamban, Meloth. National Centre for Antarctic and Ocean Research; India Fil: Trouet, Valerie. University of Arizona. Laboratory of Tree-Ring Research; Estados Unidos Fil: Turney, Chris S.M.. University of New South Wales. Climate Change Research Centre; Australia Fil: Umer, Mohammed. Addis Ababa University. School of Earth Sciences; Etiopía Fil: van Ommen, Tas. Australian Antarctic Division; Australia. University of Tasmania. Antarctic Climate & Ecosystems Cooperative Research Centre; Australia Fil: Verschuren, Dirk. Ghent University. Department of Biology; Bélgica Fil: Viau, Andre E.. University of Ottawa. Department of Geography; Canadá Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Vinther, Bo M.. University of Copenhagen. Niels Bohr Institute; Dinamarca Fil: von Gunten, Lucien . Past Global Changes (PAGES). International Project Office, ; Suiza Fil: Wagner, Sebastian. Helmholtz-Zentrum Geesthacht. Institute for Coastal Research; Alemania Fil: Wahl, Eugene R.. National Oceanic and Atmospheric Administration. National Climatic Data Center; Estados Unidos Fil: Wanner, Heinz. University of Bern. Oeschger Centre for Climate Change Research & Institute of Geography; Suiza Fil: Werner, Johannes P.. Justus Liebig University. Department of Geography, Climatology, Climate Dynamics and Climate Change; Alemania Fil: White, James W.C.. University of Colorado. Institute of Arctic and Alpine Research; Estados Unidos Fil: Yasue, Koh. Shinshu University. Department of Forest Science; Japón Fil: Zorita, Eduardo. Helmholtz-Zentrum Geesthacht. Institute for Coastal Research; Alemania