In this study, we analyzed numerical experiments undertaken by 10 climate models participating in PMIP3（Paleoclimate Modelling Intercomparison Project Phase 3） to examine the changes in interannual temperature varia...In this study, we analyzed numerical experiments undertaken by 10 climate models participating in PMIP3（Paleoclimate Modelling Intercomparison Project Phase 3） to examine the changes in interannual temperature variability and coefficient of variation（CV） of interannual precipitation in the warm period of the Medieval Climate Anomaly（MCA） and the cold period of the Little Ice Age（LIA）. With respect to the past millennium period, the MCA temperature variability decreases by 2.0% on average over the globe, and most of the decreases occur in low latitudes. In the LIA, temperature variability increases by a global average of 0.6%, which occurs primarily in the high latitudes of Eurasia and the western Pacific. For the CV of interannual precipitation, regional-scale changes are more significant than changes at the global scale, with a pattern of increased（decreased） CV in the midlatitudes of Eurasia and the northwestern Pacific in the MCA（LIA）. The CV change ranges from-7.0% to 4.3%（from -6.3% to 5.4%）, with a global average of -0.5%（-0.07%） in the MCA（LIA）.Also, the variability changes are considerably larger in December–January–February with respect to both temperature and precipitation.展开更多
Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere(NH)temperatures is necessary for understanding and attributing climate change signals during past warm and...Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere(NH)temperatures is necessary for understanding and attributing climate change signals during past warm and cold periods.However,it remains a challenge to distinguish the robust internally generated variability from the observed variability.Here,largeensemble(70 member)simulations,Energy Balance Model simulation,temperature ensemble reconstruction,and three dominant external forcings(volcanic,solar,and greenhouse gas)were combined to estimate the internal variability of NH summer(June–August)temperatures over the past 2000 years(1–2000 CE).Results indicate that the Medieval Climate Anomaly was predominantly attributed to centennial-scale internal oscillation,accounting for an estimated 104%of the warming anomaly.In contrast,the Current Warm Period is influenced mainly by external forcing,contributing up to 90%of the warming anomaly.Internal temperature variability offsets cooling by volcanic eruptions during the Late Antique Little Ice Age.These findings have important implications for the attribution of past climate variability and improvement of future climate projections.展开更多
High-resolution tree-ring δ18O chronologies covering the last millennium,although scarce,are essential in understanding patterns of climatic changes in the northeastern region of the Qinghai-Tibetan Plateau.For this ...High-resolution tree-ring δ18O chronologies covering the last millennium,although scarce,are essential in understanding patterns of climatic changes in the northeastern region of the Qinghai-Tibetan Plateau.For this study,a tree-ring δ18O chronology with a temporal resolution of 3-years was developed from the long-lived Qilian juniper(Sabina przewalskii Kom.),extending back in time to AD 991.This long δ18O chronology was significantly correlated with the yearly δ18O in tree rings during the common period from 1800 to 2006,and was an effective proxy for relative humidity during the growing season.A low-frequency moisture pattern signified the occurrence of a slight drought during the Medieval Climate Anomaly,a marked occurrence of a wet period during the Little Ice Age,and a trend in increasing moisture levels,although lower than average,alongside the Twentieth Century warming trend.Comparisons to other hydroclimatic reconstructions indicate that this tree-ring18O chronology serves as a reliable paleo-humidity proxy for the Qaidam Basin as well as documenting details of past humidity levels in the region.展开更多
The Medieval Climate Anomaly(MCA,AD950-1250)is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional wa...The Medieval Climate Anomaly(MCA,AD950-1250)is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional warming.In this study,we investigated the characteristics of temperature variations on decadal-centennial scales during the MCA for four regions(Northeast,Northwest,Central-east,and Tibetan Plateau)in China,based on high-resolution temperature reconstructions and related warm-cold records from historical documents.The ensemble empirical mode decomposition method is used to analyze the time series.The results showed that for China as a whole,the longest warm period during the last 2000 years occurred in the 10th-13th centuries,although there were multi-decadal cold intervals in the middle to late 12th century.However,in the beginning and ending decades,warm peaks and phases on the decadal scale of the MCA for different regions were not consistent with each other.On the inter-decadal scale,regional temperature variations were similar from 950 to 1130;moreover,their amplitudes became smaller,and the phases did not agree well from 1130 to 1250.On the multi-decadal to centennial scale,all four regions began to warm in the early 10th century and experienced two cold intervals during the MCA.However,the Northwest and Central-east China were in step with each other while the warm periods in the Northeast China and Tibetan Plateau ended about 40-50 years earlier.On the multi-centennial scale,the mean temperature difference between the MCA and Little Ice Age was significant in Northeast and Central-east China but not in the Northwest China and Tibetan Plateau.Compared to the mean temperature of the 20th century,a comparable warmth in the MCA was found in the Central-east China,but there was a little cooling in Northeast China;meanwhile,there were significantly lower temperatures in Northwest China and Tibetan Plateau.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.41421004)the National Key Research and Development Program of China(Grant No.2016YFA0600704)
文摘In this study, we analyzed numerical experiments undertaken by 10 climate models participating in PMIP3（Paleoclimate Modelling Intercomparison Project Phase 3） to examine the changes in interannual temperature variability and coefficient of variation（CV） of interannual precipitation in the warm period of the Medieval Climate Anomaly（MCA） and the cold period of the Little Ice Age（LIA）. With respect to the past millennium period, the MCA temperature variability decreases by 2.0% on average over the globe, and most of the decreases occur in low latitudes. In the LIA, temperature variability increases by a global average of 0.6%, which occurs primarily in the high latitudes of Eurasia and the western Pacific. For the CV of interannual precipitation, regional-scale changes are more significant than changes at the global scale, with a pattern of increased（decreased） CV in the midlatitudes of Eurasia and the northwestern Pacific in the MCA（LIA）. The CV change ranges from-7.0% to 4.3%（from -6.3% to 5.4%）, with a global average of -0.5%（-0.07%） in the MCA（LIA）.Also, the variability changes are considerably larger in December–January–February with respect to both temperature and precipitation.
基金This work was jointly funded by the National Natural Science Foundation of China(Grant Nos.41888101 and 42077406)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB26020000)+1 种基金the Key Research Program of the Institute of Geology&Geophysics,CAS(No.IGGCAS-201905)Feng Shi is funded by the Youth Innovation Promotion Association CAS.
文摘Quantitative assessment of natural internal variability and externally forced responses of Northern Hemisphere(NH)temperatures is necessary for understanding and attributing climate change signals during past warm and cold periods.However,it remains a challenge to distinguish the robust internally generated variability from the observed variability.Here,largeensemble(70 member)simulations,Energy Balance Model simulation,temperature ensemble reconstruction,and three dominant external forcings(volcanic,solar,and greenhouse gas)were combined to estimate the internal variability of NH summer(June–August)temperatures over the past 2000 years(1–2000 CE).Results indicate that the Medieval Climate Anomaly was predominantly attributed to centennial-scale internal oscillation,accounting for an estimated 104%of the warming anomaly.In contrast,the Current Warm Period is influenced mainly by external forcing,contributing up to 90%of the warming anomaly.Internal temperature variability offsets cooling by volcanic eruptions during the Late Antique Little Ice Age.These findings have important implications for the attribution of past climate variability and improvement of future climate projections.
基金supported by the Global Change Research Program of China (2010CB951401)the National Natural Science Foundation of China (41171167 and 40871002)
文摘High-resolution tree-ring δ18O chronologies covering the last millennium,although scarce,are essential in understanding patterns of climatic changes in the northeastern region of the Qinghai-Tibetan Plateau.For this study,a tree-ring δ18O chronology with a temporal resolution of 3-years was developed from the long-lived Qilian juniper(Sabina przewalskii Kom.),extending back in time to AD 991.This long δ18O chronology was significantly correlated with the yearly δ18O in tree rings during the common period from 1800 to 2006,and was an effective proxy for relative humidity during the growing season.A low-frequency moisture pattern signified the occurrence of a slight drought during the Medieval Climate Anomaly,a marked occurrence of a wet period during the Little Ice Age,and a trend in increasing moisture levels,although lower than average,alongside the Twentieth Century warming trend.Comparisons to other hydroclimatic reconstructions indicate that this tree-ring18O chronology serves as a reliable paleo-humidity proxy for the Qaidam Basin as well as documenting details of past humidity levels in the region.
基金National Key R&D Program of China,No.2017YFA0603300National Natural Science Foundation of China,No.41671036,No.41831174The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA 19040101。
文摘The Medieval Climate Anomaly(MCA,AD950-1250)is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional warming.In this study,we investigated the characteristics of temperature variations on decadal-centennial scales during the MCA for four regions(Northeast,Northwest,Central-east,and Tibetan Plateau)in China,based on high-resolution temperature reconstructions and related warm-cold records from historical documents.The ensemble empirical mode decomposition method is used to analyze the time series.The results showed that for China as a whole,the longest warm period during the last 2000 years occurred in the 10th-13th centuries,although there were multi-decadal cold intervals in the middle to late 12th century.However,in the beginning and ending decades,warm peaks and phases on the decadal scale of the MCA for different regions were not consistent with each other.On the inter-decadal scale,regional temperature variations were similar from 950 to 1130;moreover,their amplitudes became smaller,and the phases did not agree well from 1130 to 1250.On the multi-decadal to centennial scale,all four regions began to warm in the early 10th century and experienced two cold intervals during the MCA.However,the Northwest and Central-east China were in step with each other while the warm periods in the Northeast China and Tibetan Plateau ended about 40-50 years earlier.On the multi-centennial scale,the mean temperature difference between the MCA and Little Ice Age was significant in Northeast and Central-east China but not in the Northwest China and Tibetan Plateau.Compared to the mean temperature of the 20th century,a comparable warmth in the MCA was found in the Central-east China,but there was a little cooling in Northeast China;meanwhile,there were significantly lower temperatures in Northwest China and Tibetan Plateau.
