Key points on temperature change of the past 2000 years in China

Itisimportanttostudythetemperaturechangeduringthepast 2 0 0 0 yearsforunderstandingtheis suessuchasthegreenhouseeffectandglobalwarminginducedbyhumanactivities .Chinahasadvantagesinreconstructinghistoricalclimatechangeforitsabun dantdocumentedhistoricalrecordsandothernaturalevidenceobtainedfromtreerings ,lakesediments ,icecores ,andstalagmite .SinceDr .Chulaidafounda tiononthestudyoftemperaturechangeinChinaforthepast 5 0 0 0 years[1] ,significantprogressinthestudyoftemperaturechangeofthepast 2…     

A comparison of the Medieval Warm Period, Little Ice Age and 20th century warming simulated by the FGOALS climate system model

To compare differences among the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century global warming (20CW), six sets of transient and equilibrium simulations were generated using the climate system model FGOALS_gl. This model was developed by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences. The results indicate that MWP warming is evident on a global scale, except for at mid-l...     

Amplitudes, rates, periodicities and causes of temperature variations in the past 2485 years and future trends over the central-eastern Tibetan Plateau

Amplitudes, rates, periodicities, causes and future trends of temperature variations based on tree rings for the past 2485 years on the central-eastern Tibetan Plateau were analyzed. The results showed that extreme climatic events on the Plateau, such as the Medieval Warm Period, Little Ice Age and 20th Century Warming appeared synchronously with those in other places worldwide. The largest amplitude and rate of temperature change occurred during the Eastern Jin Event (343?C425 AD), and not in the late 20th century. There were significant cycles of 1324 a, 800 a, 199 a, 110 a and 2?C3 a in the 2485-year temperature series. The 1324 a, 800 a, 199 a and 110 a cycles are associated with solar activity, which greatly affects the Earth surface temperature. The long-term trends (>1000 a) of temperature were controlled by the millennium-scale cycle, and amplitudes were dominated by multi-century cycles. Moreover, cold intervals corresponded to sunspot minimums. The prediction indicated that the temperature will decrease in the future until to 2068 AD and then increase again.     

Reconstruction of temperature series of China for the last 1000 years

This paper reports a study on reconstructing temperature series for ten regions of China over the last 1000 years with a time resolution of 10 a. The regions concerned are: Northeast, North, East, South China, Taiwan, Central, Southwest, Northwest China, Xinjiang and Qinghai-Tibet Plateau. A variety of proxy data, such as ice core, tree-rings, stalagmites, peat, lake sediments, pollen and historical records, were validated with instrumental observations made in the last 120 years, and applied in the recon- struction of the temperature series. A temperature series for whole China is then established by aver- aging the ten regional series with a weighting proportional to the area of each region. Finally, tem- perature variations for the last 1000 years are examined, with special focus placed on the characteris- tics of the Medieval Warm Period (MWP), the Little Ice Age (LIA), and Modern Warming (MW).     

Characteristics of decadal-centennial-scale changes in East Asian summer monsoon circulation and precipitation during the Medieval Warm Period and Little Ice Age and in the present day

Using meteorological observations, proxies of precipitation and temperature, and climate simulation outputs, we synthetically analyzed the regularities of decadal-centennial-scale changes in the summer thermal contrast between land and ocean and summer precipitation over the East Asian monsoon region during the past millennium; compared the basic characteristics of the East Asian summer monsoon (EASM) circulation and precipitation in the present day, the Little Ice Age (LIA) and the Medieval Warm Period (MWP); and explored their links with solar irradiance and global climate change. The results indicate that over the last 150 years, the EASM circulation and precipitation, indicated by the temperature contrast between the East Asian mainland and adjacent oceans, had a significant decadal perturbation and have been weaker during the period of rapid global warming over the past 50 years. On the centennial time scale, the EASM in the MWP was strongest over the past 1000 years. Over the past 1000 years, the EASM was weakest in 1450-1570. When the EASM circulation was weaker, the monsoon rain belt over eastern China was generally located more southward, with there being less precipitation in North China and more precipitation in the Yangtze River valley; therefore, there was an anomalous pattern of southern flood/northern drought. From the 1900s to 1920s, precipitation had a pat- tern opposite to that of the southern flood/northern drought, with there being less precipitation in the Yangtze River valley and more precipitation in North China. Compared with the case for the MWP, there was a longer-time-scale southern flood/northern drought phenomenon in 1400-1600. Moreover, the EASM circulation and precipitation did not synchronously vary with the trend of global temperature. During the last 150 years, although the annual mean surface temperature around the world and in China has increased, the EASM circulation and precipitation did not have strengthening or weakening trends. Over the past 1000 years, the weakest EASM occurred ahead of the lowest Northern Hemispheric temperature and corresponded to the weakest solar irradiance.     

Temperature variations on the Tibetan Plateau over the last two millennia

The paleoclimate data recovered from ice cores,tree rings and lake sediments indicate regional features of cfimatic change on the Tibeta n Plateau (TP) during the last 2000 years. The composite temperature reconstructions in-dicate that several main climatic episodes, such as the “LittleIce Age“ between 1400 and 1900, the “Medieval Warm Pe-riod“ in 1150-1400, a less warm period in 800-1100, and an earlier cold period between the 3rd and 5th centuries,occurred in the TP. In addition, temperature varied from region to region. The period from AD 800 to 1100, which waswarm in northeastern TP, was contemporaneous with cool-ing in the western and southern TP. The southern TP ex-perienced warming between 1150 and 1400. For western TP,the δ^18O records of the Guliya ice core indicate that the pe-Hod 1250-1500 witnessed a clear warming. Large-scaletrends in the temperature history from northeastern TP aremore similar to those in eastern China than are the trendsfrom the Guliya ice cap far to the west and southern TP. The most prominent similarities between the temperature varia-tions of the TP and eastern China are such cold phases as 1100-1150, 1500-1550, 1650-1700 and 1800-1850, andthe latter three cold events match with three widespreadg lacial advances which occurred on the TP during the Little Ice A2e.     

Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean

During the last ice age, the Indian Ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial-scale climate events in the North Atlantic region, suggesting a mechanistic link. In the Holocene epoch, which had a more stable climate, the amplitude of abrupt changes in North Atlantic climate was much smaller, and it has been unclear whether these changes are related to monsoon variability. Here we present a continuous record of centennial-scale monsoon variability throughout the Holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic Arabian Sea. Our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the North Atlantic region--including the most recent climate changes from the Medieval Warm Period to the Little Ice Age and then to the present. We therefore suggest that the link between North Atlantic climate and the Asian monsoon is a persistent aspect of global climate.     

Periodic oscillations in millennial global-mean temperature and their causes

Time series of solar radiation and north Pacific sea surface temperature (SST) index were used to analyze their causality relationship with various periodic oscillations in reconstructed millennial global-mean temperature series. The three long-term periods of the Medieval Warm Period (MWP), Little Ice Age (LIA) and recent Global Warming Period (GWP) were distinct in the temperature series. 21-year, 65-year, 115-year and 200-year oscillations were derived from the temperature series after removing three long-term climatic temperatures. The phases of temperature oscillations significantly lagged behind oceanic SST and solar radiation variability. The recent decadal warm period was caused by the quasi-21-year temperature oscillation. At this century-cross period, the four oscillations reached their peaks simultaneously, which did not occur during the last millennium. Based on the long-term trend during the GWP and the four periodic oscillations, global-mean temperature is expected to drop to a new cool period in the 2030s and then a rising trend would be towards to a new warm period in the 2060s.     

Debating about the climate warming

Debating about the climate warming is reviewed. Discussions have focused on the validity of the temperature reconstruction for the last millennium made by Mann et al. Arguments against and for the reconstruction are introduced. Temperature reconstructions by other authors are examined, including the one carried out by Wang et al. in 1996. It is concluded that: (1) Ability of reproducing temperature variability of time scale less than 10 a is limited, so no sufficient evidence proves that the 1990s was the warmest decade, and 1998 was the warmest year over the last millennium. (2) All of the temperature reconstructions by different authors demonstrate the occurrence of the MWP (Medieval Warm Period) and LIA (Little Ice Age) in low frequency band of temperature variations, though the peak in the MWP and trough in LIA varies from one reconstruction to the others. Therefore, terms of MWP and LIA can be used in studies of climate change. (3) The warming from 1975 to 2000 was significant, but we do not know if it was the strongest for the last millennium, which needs to be proved by more evidence.     

Global mean temperature changes during the last millennium

A synthetic study is made on the global or hemispheric mean temperature series for the last millennium worked out by Mann et al., Jones et al., Crowley and Lowery, and Briffa. The global mean temperature series reconstructed by using proxy data at 30 sites by Wang et al. and simulations from AD 1000 to 2000 by energy balance model are described and compared with the series of others. Wang's series gives greater variability and shows the highest correlation coefficient (0.83) with the simulation results. Uncertainties in the reconstructions and simulations are discussed. The errors in reconstructing a global mean temperature series according to 30 sites as used in the research are estimated. Wang's series indicate that temperature average for the 11th century is higher than the mean of the last millennium. It infers that the Medieval Warm Period predominated to some extent over the globe. However, the 20th century is no doubt the warmest century during the last millennium.     

Characteristics of decadal-centennial-scale changes in East Asian summer monsoon circulation and precipitation during the Medieval Warm Period and Little Ice Age and in the present day

Using meteorological observations, proxies of precipitation and temperature, and climate simulation outputs, we synthetically analyzed the regularities of decadal-centennial-scale changes in the summer thermal contrast between land and ocean and summer precipitation over the East Asian monsoon region during the past millennium; compared the basic characteristics of the East Asian summer monsoon (EASM) circulation and precipitation in the present day, the Little Ice Age (LIA) and the Medieval Warm Period (MWP); and explored their links with solar irradiance and global climate change. The results indicate that over the last 150 years, the EASM circulation and precipitation, indicated by the temperature contrast between the East Asian mainland and adjacent oceans, had a significant decadal perturbation and have been weaker during the period of rapid global warming over the past 50 years. On the centennial time scale, the EASM in the MWP was strongest over the past 1000 years. Over the past 1000 years, the EASM was weakest in 1450?C1570. When the EASM circulation was weaker, the monsoon rain belt over eastern China was generally located more southward, with there being less precipitation in North China and more precipitation in the Yangtze River valley; therefore, there was an anomalous pattern of southern flood/northern drought. From the 1900s to 1920s, precipitation had a pattern opposite to that of the southern flood/northern drought, with there being less precipitation in the Yangtze River valley and more precipitation in North China. Compared with the case for the MWP, there was a longer-time-scale southern flood/northern drought phenomenon in 1400?C1600. Moreover, the EASM circulation and precipitation did not synchronously vary with the trend of global temperature. During the last 150 years, although the annual mean surface temperature around the world and in China has increased, the EASM circulation and precipitation did not have strengthening or weakening trends. Over the past 1000 years, the weakest EASM occurred ahead of the lowest Northern Hemispheric temperature and corresponded to the weakest solar irradiance.     

Forced response of atmospheric oscillations during the last millennium simulated by a climate system model

Variations in global atmospheric oscillations during the last millennium are simulated using the climate system model FGOALS_gl. The model was driven by reconstructions of both natural forcing (solar variability and volcanic aerosol) and anthropogenic forcing (greenhouse gases and sulfate aerosol). The model results are compared against proxy reconstruction data. The reconstructed North Atlantic Oscillation (NAO) was out of phase with the Pacific Decadal Oscillation (PDO) in the last millennium. During the Medieval Warm Period (MWP), the NAO was strong while the PDO was weak. During the Little Ice Age (LIA), the NAO was weak while the PDO was strong. A La Niña-like state prevailed in the MWP, while an El Niño-like state dominated in the LIA. This phenomenon is particularly obvious in the 15th, 17th and 19th centuries. Analysis of the model output indicates that the NAO was generally positive during 1000?C1400 AD and negative during 1650?C1900 AD. There is a discrepancy between the simulation and reconstruction during 1400?C1650 AD. The simulated PDO generally varies in parallel with the reconstruction, which has a negative phase during the MWP and a positive phase during the LIA. The correlation coefficient between the reconstruction and simulation is 0.61, and the correlation is statistically significant at the 1% level. Neither the La Niña-like state of the MWP nor the El Niño-like state of the LIA is reproduced in the model. Both the reconstructed and the simulated Antarctic Oscillations had a negative phase in the early period of the last millennium and a positive phase in the late period of the last millennium. The Asian-Pacific Oscillation was generally strong during the WMP and weak during the LIA, and the correlation coefficient between the simulation and reconstruction is 0.50 for the period 1000?C1985 AD. The analysis suggests that the specified external forcings significantly affected the evolution of atmospheric oscillation during the last millennium.     

过去1 300年南海东岛生态环境对气候变化的响应

东岛牛塘为目前在西沙群岛少见的淡水型湖泊,其中保存完好的粪土沉积物记录了距今1 300年来东岛生态环境演化历史.对DY4粪土沉积柱的研究结果表明,在1 400 AD前,东岛海鸟数量较多,牛塘湖岸周围植被生长较为繁盛,而在1 400~1 850 AD期间,东岛海鸟数量和植被生长都处于低谷.通过综合对比研究区、中国乃至北半球降雨量、温度变化记录,发现1 400 AD前岛屿生物量较高的时期对应于暖干的中世纪温暖期,而低生物量时期与凉湿的小冰期一致,证明南海热带孤立岛屿生态系统对区域乃至全球气候环境变化响应非常灵敏.     

A comparison of the Medieval Warm Period, Little Ice Age and 20th century warming simulated by the FGOALS climate system model

To compare differences among the Medieval Warm Period (MWP), Little Ice Age (LIA), and 20th century global warming (20CW), six sets of transient and equilibrium simulations were generated using the climate system model FGOALS_gl. This model was developed by the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences. The results indicate that MWP warming is evident on a global scale, except for at mid-latitudes of the North Pacific. However, the magnitude of the warming is weaker than that in the 20th century. The warming in the high latitudes of the Northern Hemisphere is stronger than that in the Southern Hemisphere. The LIA cooling is also evident on a global scale, with a strong cooling over the high Eurasian continent, while the cooling center is over the Arctic domain. Both the MWP and the 20CW experiments exhibit the strongest warming anomalies in the middle troposphere around 200?C300 hPa, but the cooling center of the LIA experiment is seen in the polar surface of the Northern Hemisphere. A comparison of model simulation against the reconstruction indicates that model??s performance in simulating the surface air temperature changes during the warm periods is better than that during the cold periods. The consistencies between model and reconstruction in lower latitudes are better than those in high latitudes. Comparison of the inter-annual variability mode of East Asian summer monsoon (EASM) rainfall during the MWP, LIA and 20CW reveals a similar rainfall anomalies pattern. However, the time spectra of the principal component during the three typical periods of the last millennium are different, and the quasi-biannual oscillation is more evident during the two warm periods. At a centennial time scale, the external mode of the EASM variability driven by the changes of effective solar radiation is determined by the changes of large scale land-sea thermal contrast. The rainfall anomalies over the east of 110°E exhibit a meridional homogeneous change pattern, which is different from the meridional out-of-phase change of rainfall anomalies associated with the internal mode.     

太白山西佛爷池沉积物有机碳、氮同位素记录的过去1800多年的气候-环境变化

在秦岭主峰太白山南坡的冰蚀湖西佛爷池中取得一个深50cm 的沉积物柱芯(XFYC12-2)。对XFYC12-2的样品做加速器质谱(AMS) ¹⁴C 测年和有机碳、氮稳定同位素分析, 并据此重建这一高山湖泊周边过去1800多年的气候−环境变化。结果表明: 1811~1380 (或1440) aBP 偏冷干; 1380 (或1440)~840 aBP 温暖湿润, 这一阶段可能与中世纪暖期相当; 840~460 (或 520) aBP 转为寒冷干旱, 这一阶段或许相当于小冰期; 460(或 520)~100 aBP 又趋暖湿。上述气候?环境变化过程与太白山南坡高海拔地段另外两个湖附近的变化过程、中国东部地区的总体变化趋势及4 个代表性地点的变化过程相似。     

Reconstruction and analysis of time series of ENSO for the last 500 years

This paper reports the classification of ENSO into seven categories according to annual (March to February of next year) mean SST of Ni(n)o 3.4 and composite index (ΔI) for the period of 1861～2000. Categories +3, +2, and +1 denote very strong, strong and weak warm episodes (E), -3, -2, and -1 mean very strong, strong and weak cold episodes (A). Absolute SST anomalies are about 1.5 ℃, 1.0 ℃ and 0.5 ℃ respectively for the categories 3, 2, and 1 (or -3, -2, and -1). The normal years are expressed as category 0. Annual categories of ENSO are estimated on the basis of proxy data from AD 1501 to 1860. And a series of ENSO category is established for the period of 1501～2000 in conjunction with the observational data. Comparison of proxy data with observations for 1874～1973 indicates that about 80% of the El Ni(n)o years and La Ni(n)a years can be reconstructed from proxy data, and the reliability of the reconstruction is verified. Analysis of the power spectrum of the reconstructed ENSO series shows significant peaks at QBO, 3～4a (year), 5～6a, and 10a period, the former three are in accordance with the observations for the last 100 years or more. Studies on long term variability of ENSO indicates that ENSO frequency is relatively stationary during the last 500 years, including the Little Ice Age (LIA) (1550～1850) and Modern Warming Period (the 20th century). However, the frequency of E is a little higher in the 20th century and that of A is somewhat higher during the LIA.     

中国中世纪暖期温度的时空变化特征

采用全球海气耦合模式ECHO-G的1000个模式年的长积分气候模拟方法分析了中国中世纪暖期温度的存在性与时空变化特征.结果表明：中国的中世纪暖期出现在公元1000—1250年间,但它不是一个持续稳定的暖期,而是存在峰谷起伏变化,其中最暖的30年（中世纪暖期鼎盛期）出现在1131—1160年.中世纪暖期中国的年平均和冬、夏季平均温度距平变幅西部最大,东部最小.其鼎盛期中国的温度距平相对于千年温度都是正值,中国东部的增温幅度由南向北逐渐加大,变幅为0.4℃—0.8℃,而中国西部的增温呈Ω型分布,且随着海拔高度的增加,增温幅度逐渐加大,最大增温达2.0℃—2.2℃.     

Simulated and reconstructed winter temperature in the eastern China during the last millennium

Since the 1990s, under the auspicious impetus of two international research programs, the “Past Global Changes” (PAGES) and the “Climate Variability and Pre- dictability” (CLIVAR), massive research work has been carried out on climate and environment changes over the past 2000 years[1-3]. But majority of the studies has been centered on obtaining various kinds of climatic proxy data (such as historical documents, tree rings, ice cores, lake cores) and focused on the reconstruction of…     

Late Holocene paleoenvironmental changes in the southern Okinawa Trough inferred from a diatom record

We analyzed sediment diatoms from core MD05-2908 to infer climate and paleoenvironmental changes in the southern Okinawa Trough (SOT) over the past 1000 years.Because the study area is located in the East Asia monsoon area and beneath the main axis of Kuroshio Current,the climatic and hydrographical conditions are strongly influenced by both of these factors.The species used as environmental indicators,including the Kuroshio Current species (KC species) and freshwater species,were investigated in this paper.Changes in the abundance of the two groups of species revealed significant variations in water temperature and hydrography in the SOT during the Medieval Warm Period (MWP) and the Little Ice Age (LIA).From 950-1500 AD,the abundance of the KC species increased fluctuantly,while the freshwater species decreased,showing that the influence of the Kuroshio Current was intensified at that interval and the precipitation of the study area was relatively low.The KC species decreased remarkably and was maintained at a low abundance during the interval of 1500-1900 AD,which suggests that the impact of the Kuroshio Current on the SOT weakened during the period corresponding to the LIA.Moreover,the high abundance of the freshwater species at the same interval indicates a distinct increase in precipitation in northeastern Taiwan,which may be correlated to the south-detention of the rainfall belt in China caused by the southward migration of the western Pacific subtropical high.     

鄱阳湖沙山高分辨率沙质地层及其冬季风气候信息记录的初步探究

位于鄱阳湖流域的长江、赣江等河谷、河漫滩的下风方向,由于处于冬季风强烈的东亚季风区,在高频率出现的大风、强风天气情况下,受风力吹蚀作用,常形成区域性的沙山堆积.沙山纵向垄状地形发育,其上风方向,槽、沟与碟形坑等侵蚀地貌发育,其下风方向,纵向沙垄发育.通过对样品的光释光年代测试和粒度频数分析,浅析星子PBL剖面的小冰期风积地层,揭示了小冰期晚期持续近60年左右的一次冷期,这个冷期以突变开始,以渐变结束,其清晰程度在其它地质记录中是不曾发现的.研究发现鄱阳湖沙山纵向沙垄往往具有缓倾斜的前积与侧积,层理(薄层与细层)往往较稳定,对揭露冬季风气候信息具有重要的意义.