Chun Qin - Academia.edu (original) (raw)
Papers by Chun Qin
Russian Meteorology and Hydrology, Oct 1, 2021
The spectral composition of temporal variations in the Northern Hemisphere mean surface air tempe... more The spectral composition of temporal variations in the Northern Hemisphere mean surface air temperature is estimated and compared in 2000-year paleoclimatic reconstructions. Continuous wavelet transforms of these reconstructions are used for the stable estimation of energy spectra. It is found that low-frequency parts of the spectra (the periods of temperature variations of more than 100 years) based on such high-resolution paleoclimatic indicators as tree rings, corals, etc., are similar to the spectrum of white noise, that is never observed in nature. This seems unrealistic. The famous reconstruction called “Hockey Stick” is among such unrealistic reconstructions. Reconstructions based not only on high-resolution but also on low-resolution indicators seem to be more realistic, since the low-frequency parts of their spectra have the pattern of red noise. They include the “Boomerang” reconstruction showing that some warm periods close to the present-day one were observed in the past.
Proceedings of the National Academy of Sciences of the United States of America, May 13, 2022
Science China-earth Sciences, May 18, 2021
Almost all proxy-based temperature reconstructions for East Asia have hitherto been designed to r... more Almost all proxy-based temperature reconstructions for East Asia have hitherto been designed to resolve summer or annual temperature variability. Reconstruction for the winter temperature is still lacking. Here, we report an annually resolved, winter-season (December-February, DJF) temperature field reconstruction for East Asia covering the period 1300–2000 CE, based on 260 temperature-sensitive tree-ring records. The most striking feature of our new reconstruction is a significant long-term warming trend since the 14th century, which is associated with winter solar insolation at mid-latitudes of the Northern Hemisphere and the global anthropogenic impact. The amplitude of reconstructed winter temperature change over the study period was ~4.7 times greater than that for summer temperature, and the rate of winter temperature increase was ∼6 times as much as that of summer temperature. The results from climate model simulations were consistent with the reconstruction, showing that the amplitude and rate of temperature change in winter were greater than those in summer. The reconstruction also suggests the possible influence of volcanic eruptions, anthropogenic activities and winter solar insolation on the winter temperature variations. Our result also suggests a long-term decrease in summer-to-winter temperature difference occurred in 1625 (±24 years) CE.
Quaternary International, May 1, 2011
Theoretical and Applied Climatology, Dec 30, 2011
Forests, 2022
Carbon and oxygen isotope ratios (δ13C and δ18O) were measured in annual tree-ring cellulose samp... more Carbon and oxygen isotope ratios (δ13C and δ18O) were measured in annual tree-ring cellulose samples dated from 1756 to 2015 CE. These samples were extracted from Chinese pine (Pinus tabulaeformis Carr.) trees located in a semi-arid region of north-central China. We found that tree-ring δ13C and δ18O values both recorded similar climatic signals (e.g., temperature and moisture changes), but found that tree-ring δ13C exhibited a stronger relationship with mean temperature, precipitation, average relative humidity, self-calibrating Palmer drought severity index (scPDSI), and standard precipitation evaporation index (SPEI) than δ18O during the period 1951–2015 CE. The strongest correlation observed was between tree-ring δ13C and scPDSI (previous June to current May), which explains ~43% of the variance. The resulting 130-year reconstruction reveals severe drought events in the 1920s and a sustained drying trend since the 1980s. This hydroclimate record based on tree-ring δ13C data also...
Sciences in Cold and Arid Regions, 2012
Traditional dendroclimatology research is based on the statistical correlation between tree-ring ... more Traditional dendroclimatology research is based on the statistical correlation between tree-ring chronology and modern observation data, but lacks consideration of the mechanisms of tree-ring growth. In order to reconstruct past climatic conditions more reliably, the response of stem radius growth dynamics should be studied in detail. At present, in international researches, monitoring and simulation methods are generally treated as two separate approaches. The monitoring method generally consists of dendrometer measurements, micro-coring, and pinning. Here, we present the research progress of stem radius growth dynamics studies derived from these methods, and provide prospects for future study.
Ying yong sheng tai xue bao = The journal of applied ecology, 2021
The stem radius growth of Pinus tabuliformis was monitored by dendrometer during the growing seas... more The stem radius growth of Pinus tabuliformis was monitored by dendrometer during the growing season in 2017 and 2018 at two altitudes (2010 and 2330 m) in the Helan Mountains. We investigated the responses of tree radial growth to drought events. The results showed that drought event in June 2018 reduced stem growth rate of P. tabuliformis. The precipitation in July and August reactivated the stem radius growth. The main growing season of P. tabuliformis stem was June-August in 2018, which was a month longer than that in 2017. The response patterns between stem radial growth of P. tabuliformis and climatic factors were consistent across forest stands in different altitudes. Drought in the early growing season suppressed the radial growth of trees, while precipitation in the mid- and late growing seasons played an important role in promoting the radial growth of trees. The effects of climatic factors in August on tree-ring width should be considered during climate reconstruction in t...
Age is the sole criterion for identifying ancient trees. Dendrochronology was used to examine the... more Age is the sole criterion for identifying ancient trees. Dendrochronology was used to examine the age of the old trees of Pyrus ussuriensis in the Fourth group of Doujiadun Village (formerly Yangjiayuanzi), Mogao Town, Dunhuang City. As all the old pear trees had been decayed and hollow, we collected cores of P. ussuriensis of different ages to establish the age-related curve of tree radial growth, and estimated the number of tree rings in the missing segment. Combined with accurate count on tree rings, the age of P. ussuriensis was restored. The results showed that the average age of the 13 old pear trees in the orchard was (280±35) years, presenting further evidence for the record about old pear trees in Dunhuang Zhi. These old trees could be classified as the third-class ancient tree according to tree age, and should be properly protected and preserved. This study provided a detailed scientific basis to resolve the dispute over the conservation of ancient P. ussuriensis in Dunhua...
Proceedings of the National Academy of Sciences, 2021
Significance The variability of the Asian summer monsoon (ASM) is important for the functioning o... more Significance The variability of the Asian summer monsoon (ASM) is important for the functioning of ecological and societal systems at regional to continental scales, but the long-term evolution and interannual variability of this system is not well understood. Here, we present a stable isotope–based reconstruction of ASM variability covering 4680 BCE to 2011 CE. Superimposed on a gradual drying trend, a rapid drop in mean annual precipitation (>40%) toward persistently drier conditions occurred in ∼1675 BCE. This megadrought caused regional forest deterioration and enhanced aeolian activity affecting Chinese ecosystems. We argue that this abrupt aridification starting ∼2000 BCE triggered waves of human migration and societal transformation in northern China, which contributed to the alteration of spatial pattern of ancient civilizations.
Atmosphere, 2020
Although cambial reactivation is considered to be strongly dependent on temperature, the importan... more Although cambial reactivation is considered to be strongly dependent on temperature, the importance of water availability at the onset of xylogenesis in semi-arid regions still lacks sufficient evidences. In order to explore how environmental factors influence the initiation of cambial activity and wood formation, we monitored weekly cambial phenology in Qilian juniper (Juniperus przewalskii) from a semi-arid high-elevation region of northwestern China. We collected microcores from 12 trees at two elevations during the growing seasons in 2013 and 2014, testing the hypothesis that rainfall limits cambial reactivation in spring. Cambium was reactivated from late April to mid-May, and completed cell division from late July to early August, lasting 70–100 days. Both sites suffered from severe drought from January to April 2013, receiving < 1 mm of rain in April. In contrast, rainfall from January to April 2014 was 5–6 times higher than that in 2013. However, cambial reactivation in 2...
Dendrochronologia, 2017
This paper describes a tree-ring width chronology that spans the past 4650 years, established usi... more This paper describes a tree-ring width chronology that spans the past 4650 years, established using the recently developed eigenanalysis technique. The aim is to show whether this eigenanalysis method enables the extraction of long-term tree-growth variations that are due to climatic changes, from a large dataset comprising 1263 treering width records sampled from the highlands of Western China. In order to exclude the so-called growth rate/ life span association effect, tree-ring width records were sorted into six subsets, based on the life spans of the trees sampled: 200-400, 400-600, 600-800, 800-1000, 1000-1500 years old, and trees older than 1500 years. Some partial chronologies were created, by pairing the set of all tree samples (living, dead, archaeological remains) with the living trees belonging to each subset. We computed the contours of tree-growth variations (on both 100-year and longer time scales) for each subset, ending with six pairs of these partial subset chronologies. Two sums of all these partial chronologies thus yielded a record of precipitation variations over a period ranging from 2627 BCE up to 2012 CE. It was found that this record shows a high degree of similarity to the existing chronology produced using the regional curve standardization (RCS) method applied to the same dataset, indicating that the eigenvalue chronology is capable of faithfully extracting long-term climatic variations. This also confirms that the first eigenvector represents the growth pattern that is characteristic of each biologically unique tree as well as the micro-environment of each tree stand. The variations observed over the last millennium seem to be connected to a cycle of solar activity with a period of ∼200 years. However, a clear lack of correspondence between solar activity and tree growth prior to 1000 CE indicates that the recent consistency may be coincidental. We believe that the eigenanalysis technique is readily applicable to other kinds of tree-ring datasets from different parts of the world.
Earth-Science Reviews, 2019
Considerable progress has been made in dendroclimatological research in China during the period 2... more Considerable progress has been made in dendroclimatological research in China during the period 2000-2017, including a significant increase in the spatial coverage of tree-ring chronologies developed for paleoclimatic research. New tree-ring sampling sites have been established across the Tibetan Plateau, as well as the northeastern and subtropical eastern parts of China. Most of the studies use coniferous trees, although different plant functional types (e.g., broadleaf species and shrubs) have also been increasingly investigated. Tree-ring chronologies longer than 600 years, however, are only found on the Tibetan Plateau, with the longest one extending back to 2637 BC (before Christ). Most tree-ring records in the eastern parts of China are still less than 400 years long. Tree-ring width is the most commonly studied parameter, although stable isotope ratios and wood density data have also been obtained for specific sites. Stable oxygen isotope data frequently shares a common hydroclimate signal, whereas the climate or environmental signals remain inconsistent for the few available stable carbon isotope records. In general, tree-ring width-based temperature reconstructions originate from higher elevation sites (i.e., treeline) compared to hydroclimate reconstructions. Precipitation or drought reconstructions are mainly obtained from regions with an annual precipitation of less than 800 mm. Most of the tree-ring reconstructions are based on individual site or local-scale chronologies, although a limited number of regional-scale and field reconstructions have been produced. The most prominent identified aspects of the recent advances in dendroclimatolo gical research for China have manifested in
The Holocene, 2011
We developed two tree ring-width chronologies (Qilian juniper, Sabina przewalskii Kom.) for the i... more We developed two tree ring-width chronologies (Qilian juniper, Sabina przewalskii Kom.) for the inland Heihe River Basin in arid northwest China using a large number of tree-ring samples (217 samples/92 trees) with accurate information about pith offsets based on Regional Curve Standardization (RCS) and standard dendrochronological (STD) methodologies. Two 1422-year reconstructions of annual (August–July) streamflow for the upstream region of the Heihe River are presented. The STD and RCS reconstructions account for 53.4% and 57.2% of the actual streamflow variance during the period 1958–2006, respectively. Both reconstructions display considerable low frequency (multidecadal to multicentury) fluctuations, although the RCS based reconstruction is superior to the STD based reconstruction for retention of low-frequency trends. Low-flow years in ad 818–852, 1112–1196, 1453–1495 and 1680–1710, and high-flow periods in ad 868–1000, 1056–1094, 1228–1271, 1327–1440, 1510–1583 and 1877–2006...
Russian Meteorology and Hydrology, 2014
ABSTRACT Comparison with the climate of the past centuries has demonstrated until recently the un... more ABSTRACT Comparison with the climate of the past centuries has demonstrated until recently the unprecedented warming at the scale of the last millennium at least. This is embodied in the latest report of the Intergovernmental Panel on Climate Change. However, recently the studies have appeared putting this statement into question. A new 1000-year long reconstruction based on the tree-ring variations of the long-living Chinese junipers (Sabina Przewalskii Kom.) growing in the northeastern part of the Tibetan Plateau reveals that the climate during and immediately after the medieval maximum of solar activity was warmer that the present-day one, all subsequent cooling coincided with the periods of low solar activity, and the warming in the 1970s–1990s followed a new maximum of the solar activity which peak fell on the 1960s.
Global and Planetary Change, 2015
oxygen isotopes wood cellulose Sabina przewalskii hydroclimate Northeast Tibetan plateau For the ... more oxygen isotopes wood cellulose Sabina przewalskii hydroclimate Northeast Tibetan plateau For the mechanistic understanding of hydroclimate variability, stable oxygen isotopic ratios (δ 18 O) of tree-ring α-cellulose can play a key role in paleoclimatic research. On the northeast Tibetan Plateau (TP), a region particularly sensitive to climate change, there exists a distinct lack of δ 18 O research in tree-ring archives. The few currently existing tree-ring δ 18 O chronologies were obtained by pooling the wood material from the same year from different trees prior to preparation and analysis. Although this method is time and cost efficient, it might impede the analysis of changes within the internal variability of oxygen isotope signals and a deeper understanding of the resulting climate reconstruction. We selected five Qilian juniper (Sabina przewalskii Kom.) trees covering the period 1951-2011 on the northeast TP to investigate the climate signals contained in stable oxygen isotopic composition records obtained using single tree analysis. Although the inter-series correlation between the five individual δ 18 O series indicates a highly significant relationship (mean r = 0.59, n = 59, p = 0.01), the five individual δ 18 O series show significantly differently mean values. We found significant negative correlations between drought/hydroclimatically triggered climate parameters (PDSI, precipitation) and each of the individual δ 18 O series. Spatial correlation maps indicate negative correlation of tree-ring δ 18 O and Indian Ocean sea surface temperatures, and inverse correlation patters of moisture conditions on the northern and southern TP. Our results provide a reference for future research on stable oxygen isotope/climate signals in the species S. przewalskii Kom..
Russian Meteorology and Hydrology, Oct 1, 2021
The spectral composition of temporal variations in the Northern Hemisphere mean surface air tempe... more The spectral composition of temporal variations in the Northern Hemisphere mean surface air temperature is estimated and compared in 2000-year paleoclimatic reconstructions. Continuous wavelet transforms of these reconstructions are used for the stable estimation of energy spectra. It is found that low-frequency parts of the spectra (the periods of temperature variations of more than 100 years) based on such high-resolution paleoclimatic indicators as tree rings, corals, etc., are similar to the spectrum of white noise, that is never observed in nature. This seems unrealistic. The famous reconstruction called “Hockey Stick” is among such unrealistic reconstructions. Reconstructions based not only on high-resolution but also on low-resolution indicators seem to be more realistic, since the low-frequency parts of their spectra have the pattern of red noise. They include the “Boomerang” reconstruction showing that some warm periods close to the present-day one were observed in the past.
Proceedings of the National Academy of Sciences of the United States of America, May 13, 2022
Science China-earth Sciences, May 18, 2021
Almost all proxy-based temperature reconstructions for East Asia have hitherto been designed to r... more Almost all proxy-based temperature reconstructions for East Asia have hitherto been designed to resolve summer or annual temperature variability. Reconstruction for the winter temperature is still lacking. Here, we report an annually resolved, winter-season (December-February, DJF) temperature field reconstruction for East Asia covering the period 1300–2000 CE, based on 260 temperature-sensitive tree-ring records. The most striking feature of our new reconstruction is a significant long-term warming trend since the 14th century, which is associated with winter solar insolation at mid-latitudes of the Northern Hemisphere and the global anthropogenic impact. The amplitude of reconstructed winter temperature change over the study period was ~4.7 times greater than that for summer temperature, and the rate of winter temperature increase was ∼6 times as much as that of summer temperature. The results from climate model simulations were consistent with the reconstruction, showing that the amplitude and rate of temperature change in winter were greater than those in summer. The reconstruction also suggests the possible influence of volcanic eruptions, anthropogenic activities and winter solar insolation on the winter temperature variations. Our result also suggests a long-term decrease in summer-to-winter temperature difference occurred in 1625 (±24 years) CE.
Quaternary International, May 1, 2011
Theoretical and Applied Climatology, Dec 30, 2011
Forests, 2022
Carbon and oxygen isotope ratios (δ13C and δ18O) were measured in annual tree-ring cellulose samp... more Carbon and oxygen isotope ratios (δ13C and δ18O) were measured in annual tree-ring cellulose samples dated from 1756 to 2015 CE. These samples were extracted from Chinese pine (Pinus tabulaeformis Carr.) trees located in a semi-arid region of north-central China. We found that tree-ring δ13C and δ18O values both recorded similar climatic signals (e.g., temperature and moisture changes), but found that tree-ring δ13C exhibited a stronger relationship with mean temperature, precipitation, average relative humidity, self-calibrating Palmer drought severity index (scPDSI), and standard precipitation evaporation index (SPEI) than δ18O during the period 1951–2015 CE. The strongest correlation observed was between tree-ring δ13C and scPDSI (previous June to current May), which explains ~43% of the variance. The resulting 130-year reconstruction reveals severe drought events in the 1920s and a sustained drying trend since the 1980s. This hydroclimate record based on tree-ring δ13C data also...
Sciences in Cold and Arid Regions, 2012
Traditional dendroclimatology research is based on the statistical correlation between tree-ring ... more Traditional dendroclimatology research is based on the statistical correlation between tree-ring chronology and modern observation data, but lacks consideration of the mechanisms of tree-ring growth. In order to reconstruct past climatic conditions more reliably, the response of stem radius growth dynamics should be studied in detail. At present, in international researches, monitoring and simulation methods are generally treated as two separate approaches. The monitoring method generally consists of dendrometer measurements, micro-coring, and pinning. Here, we present the research progress of stem radius growth dynamics studies derived from these methods, and provide prospects for future study.
Ying yong sheng tai xue bao = The journal of applied ecology, 2021
The stem radius growth of Pinus tabuliformis was monitored by dendrometer during the growing seas... more The stem radius growth of Pinus tabuliformis was monitored by dendrometer during the growing season in 2017 and 2018 at two altitudes (2010 and 2330 m) in the Helan Mountains. We investigated the responses of tree radial growth to drought events. The results showed that drought event in June 2018 reduced stem growth rate of P. tabuliformis. The precipitation in July and August reactivated the stem radius growth. The main growing season of P. tabuliformis stem was June-August in 2018, which was a month longer than that in 2017. The response patterns between stem radial growth of P. tabuliformis and climatic factors were consistent across forest stands in different altitudes. Drought in the early growing season suppressed the radial growth of trees, while precipitation in the mid- and late growing seasons played an important role in promoting the radial growth of trees. The effects of climatic factors in August on tree-ring width should be considered during climate reconstruction in t...
Age is the sole criterion for identifying ancient trees. Dendrochronology was used to examine the... more Age is the sole criterion for identifying ancient trees. Dendrochronology was used to examine the age of the old trees of Pyrus ussuriensis in the Fourth group of Doujiadun Village (formerly Yangjiayuanzi), Mogao Town, Dunhuang City. As all the old pear trees had been decayed and hollow, we collected cores of P. ussuriensis of different ages to establish the age-related curve of tree radial growth, and estimated the number of tree rings in the missing segment. Combined with accurate count on tree rings, the age of P. ussuriensis was restored. The results showed that the average age of the 13 old pear trees in the orchard was (280±35) years, presenting further evidence for the record about old pear trees in Dunhuang Zhi. These old trees could be classified as the third-class ancient tree according to tree age, and should be properly protected and preserved. This study provided a detailed scientific basis to resolve the dispute over the conservation of ancient P. ussuriensis in Dunhua...
Proceedings of the National Academy of Sciences, 2021
Significance The variability of the Asian summer monsoon (ASM) is important for the functioning o... more Significance The variability of the Asian summer monsoon (ASM) is important for the functioning of ecological and societal systems at regional to continental scales, but the long-term evolution and interannual variability of this system is not well understood. Here, we present a stable isotope–based reconstruction of ASM variability covering 4680 BCE to 2011 CE. Superimposed on a gradual drying trend, a rapid drop in mean annual precipitation (>40%) toward persistently drier conditions occurred in ∼1675 BCE. This megadrought caused regional forest deterioration and enhanced aeolian activity affecting Chinese ecosystems. We argue that this abrupt aridification starting ∼2000 BCE triggered waves of human migration and societal transformation in northern China, which contributed to the alteration of spatial pattern of ancient civilizations.
Atmosphere, 2020
Although cambial reactivation is considered to be strongly dependent on temperature, the importan... more Although cambial reactivation is considered to be strongly dependent on temperature, the importance of water availability at the onset of xylogenesis in semi-arid regions still lacks sufficient evidences. In order to explore how environmental factors influence the initiation of cambial activity and wood formation, we monitored weekly cambial phenology in Qilian juniper (Juniperus przewalskii) from a semi-arid high-elevation region of northwestern China. We collected microcores from 12 trees at two elevations during the growing seasons in 2013 and 2014, testing the hypothesis that rainfall limits cambial reactivation in spring. Cambium was reactivated from late April to mid-May, and completed cell division from late July to early August, lasting 70–100 days. Both sites suffered from severe drought from January to April 2013, receiving < 1 mm of rain in April. In contrast, rainfall from January to April 2014 was 5–6 times higher than that in 2013. However, cambial reactivation in 2...
Dendrochronologia, 2017
This paper describes a tree-ring width chronology that spans the past 4650 years, established usi... more This paper describes a tree-ring width chronology that spans the past 4650 years, established using the recently developed eigenanalysis technique. The aim is to show whether this eigenanalysis method enables the extraction of long-term tree-growth variations that are due to climatic changes, from a large dataset comprising 1263 treering width records sampled from the highlands of Western China. In order to exclude the so-called growth rate/ life span association effect, tree-ring width records were sorted into six subsets, based on the life spans of the trees sampled: 200-400, 400-600, 600-800, 800-1000, 1000-1500 years old, and trees older than 1500 years. Some partial chronologies were created, by pairing the set of all tree samples (living, dead, archaeological remains) with the living trees belonging to each subset. We computed the contours of tree-growth variations (on both 100-year and longer time scales) for each subset, ending with six pairs of these partial subset chronologies. Two sums of all these partial chronologies thus yielded a record of precipitation variations over a period ranging from 2627 BCE up to 2012 CE. It was found that this record shows a high degree of similarity to the existing chronology produced using the regional curve standardization (RCS) method applied to the same dataset, indicating that the eigenvalue chronology is capable of faithfully extracting long-term climatic variations. This also confirms that the first eigenvector represents the growth pattern that is characteristic of each biologically unique tree as well as the micro-environment of each tree stand. The variations observed over the last millennium seem to be connected to a cycle of solar activity with a period of ∼200 years. However, a clear lack of correspondence between solar activity and tree growth prior to 1000 CE indicates that the recent consistency may be coincidental. We believe that the eigenanalysis technique is readily applicable to other kinds of tree-ring datasets from different parts of the world.
Earth-Science Reviews, 2019
Considerable progress has been made in dendroclimatological research in China during the period 2... more Considerable progress has been made in dendroclimatological research in China during the period 2000-2017, including a significant increase in the spatial coverage of tree-ring chronologies developed for paleoclimatic research. New tree-ring sampling sites have been established across the Tibetan Plateau, as well as the northeastern and subtropical eastern parts of China. Most of the studies use coniferous trees, although different plant functional types (e.g., broadleaf species and shrubs) have also been increasingly investigated. Tree-ring chronologies longer than 600 years, however, are only found on the Tibetan Plateau, with the longest one extending back to 2637 BC (before Christ). Most tree-ring records in the eastern parts of China are still less than 400 years long. Tree-ring width is the most commonly studied parameter, although stable isotope ratios and wood density data have also been obtained for specific sites. Stable oxygen isotope data frequently shares a common hydroclimate signal, whereas the climate or environmental signals remain inconsistent for the few available stable carbon isotope records. In general, tree-ring width-based temperature reconstructions originate from higher elevation sites (i.e., treeline) compared to hydroclimate reconstructions. Precipitation or drought reconstructions are mainly obtained from regions with an annual precipitation of less than 800 mm. Most of the tree-ring reconstructions are based on individual site or local-scale chronologies, although a limited number of regional-scale and field reconstructions have been produced. The most prominent identified aspects of the recent advances in dendroclimatolo gical research for China have manifested in
The Holocene, 2011
We developed two tree ring-width chronologies (Qilian juniper, Sabina przewalskii Kom.) for the i... more We developed two tree ring-width chronologies (Qilian juniper, Sabina przewalskii Kom.) for the inland Heihe River Basin in arid northwest China using a large number of tree-ring samples (217 samples/92 trees) with accurate information about pith offsets based on Regional Curve Standardization (RCS) and standard dendrochronological (STD) methodologies. Two 1422-year reconstructions of annual (August–July) streamflow for the upstream region of the Heihe River are presented. The STD and RCS reconstructions account for 53.4% and 57.2% of the actual streamflow variance during the period 1958–2006, respectively. Both reconstructions display considerable low frequency (multidecadal to multicentury) fluctuations, although the RCS based reconstruction is superior to the STD based reconstruction for retention of low-frequency trends. Low-flow years in ad 818–852, 1112–1196, 1453–1495 and 1680–1710, and high-flow periods in ad 868–1000, 1056–1094, 1228–1271, 1327–1440, 1510–1583 and 1877–2006...
Russian Meteorology and Hydrology, 2014
ABSTRACT Comparison with the climate of the past centuries has demonstrated until recently the un... more ABSTRACT Comparison with the climate of the past centuries has demonstrated until recently the unprecedented warming at the scale of the last millennium at least. This is embodied in the latest report of the Intergovernmental Panel on Climate Change. However, recently the studies have appeared putting this statement into question. A new 1000-year long reconstruction based on the tree-ring variations of the long-living Chinese junipers (Sabina Przewalskii Kom.) growing in the northeastern part of the Tibetan Plateau reveals that the climate during and immediately after the medieval maximum of solar activity was warmer that the present-day one, all subsequent cooling coincided with the periods of low solar activity, and the warming in the 1970s–1990s followed a new maximum of the solar activity which peak fell on the 1960s.
Global and Planetary Change, 2015
oxygen isotopes wood cellulose Sabina przewalskii hydroclimate Northeast Tibetan plateau For the ... more oxygen isotopes wood cellulose Sabina przewalskii hydroclimate Northeast Tibetan plateau For the mechanistic understanding of hydroclimate variability, stable oxygen isotopic ratios (δ 18 O) of tree-ring α-cellulose can play a key role in paleoclimatic research. On the northeast Tibetan Plateau (TP), a region particularly sensitive to climate change, there exists a distinct lack of δ 18 O research in tree-ring archives. The few currently existing tree-ring δ 18 O chronologies were obtained by pooling the wood material from the same year from different trees prior to preparation and analysis. Although this method is time and cost efficient, it might impede the analysis of changes within the internal variability of oxygen isotope signals and a deeper understanding of the resulting climate reconstruction. We selected five Qilian juniper (Sabina przewalskii Kom.) trees covering the period 1951-2011 on the northeast TP to investigate the climate signals contained in stable oxygen isotopic composition records obtained using single tree analysis. Although the inter-series correlation between the five individual δ 18 O series indicates a highly significant relationship (mean r = 0.59, n = 59, p = 0.01), the five individual δ 18 O series show significantly differently mean values. We found significant negative correlations between drought/hydroclimatically triggered climate parameters (PDSI, precipitation) and each of the individual δ 18 O series. Spatial correlation maps indicate negative correlation of tree-ring δ 18 O and Indian Ocean sea surface temperatures, and inverse correlation patters of moisture conditions on the northern and southern TP. Our results provide a reference for future research on stable oxygen isotope/climate signals in the species S. przewalskii Kom..