Shi Yafeng

General characteristics of temperature variation in China during the last two millennia

Three alternate China-wide temperature composites covering the last 2000 years were established by combining multiple paleoclimate proxy records obtained from ice cores, tree rings, lake sediments and historical documents. Five periods of temperature variation can be identified: a warm stage in AD 0–240, a cold interval between AD 240 and 800, a return to warm conditions from AD 800–1400, including the Medieval Warm Period between AD 800–1100, the cool Little Ice Age period between 1400–1920, and the present warm stage since 1920. Regional temperature variation is found during AD 800–1100, when warm conditions occurred in Eastern China and in the northeastern Tibetan Plateau and in AD 1150–1380, when the southern Tibetan Plateau experienced a warm interval. In contrast, evidence for cool conditions during the LIA is more consistent among the proxy records. The temperature reconstructions for China and the Northern Hemisphere show good agreement over the past millennium.

Mid-holocene climates and environments in China

Abstract This paper focuses mainly on the climatic and environmental variations 5 to 3 ka. B.P. with particular reference to one stable warmer and wetter millennium (7.2-6 ka B.P.). Some large-scale centennial warming was accompanied by an increase in precipitation owing to the expansion of the monsoon circulation, e.g. rapid warming during the period from 8.5 to 8.3 ka B.P. and was reflected in the high level of some inland lakes and the sudden expansion of vegetation in pollen diagrams. The growth of the Neolithic culture with agriculture and settlement in the present semi-arid area of Northwest China was undoubtedly related to the dramatic warming and wetting before 8 ka B.P. According to the proxy data of palynological studies, the deviation of annual mean temperature from todays about 7-6 ka B.P. was roughly estimated at about 1°C in South China, 2°C in the Changjiang (Yangtze) Valley, 3°C in North China and Northeast China. The strongest warming by 4–5°C was recorded in Qinghai-Xizang (Tibet) Plateau. The winter temperature rise was much greater than the annual average temperature. In the eastern half of China, the vegetation zones are mainly parallel to the latitude. During the climax of the Holocene warm period, the northern limit of the tropical monsoonal rain forest shifted less than 1° of latitude northward, the subtropical broad-leaved evergreen forest about 1° of latitude, the north subtropical deciduous and evergreen broad-leaved mixed forest about 3° of latitude in the coastal area but only 1–1.5° of latitude in mid-West China and the warm temperate deciduous forest moved 4° of latitude northward, greatly expanding its distribution. Further north, the cool temperate boreal forest withdrew from its southern boundary by about 2° of latitude. Global climatic warming in the mid-Holocene resulted in a sea-level rise. During the period from 6 to 5 ka BP. the sea-level was about 1–3 m higher than the present level. Large area of coastal lowland was submerged by sea water and frequency of occurrence of storm surges also increased during the high sea-level period.

Late Holocene temperature fluctuations on the Tibetan Plateau.

Abstract Proxy data of palaeoclimate, like ice cores, tree rings and lake sediments, document aspects of climate changes on the Tibetan Plateau during the last 2000 years. The results show that the Tibetan Plateau experienced climatic episodes such as the warm intervals during AD 800–1100 and 1150–1400, the “Little Ice Age” between AD 1400 and 1900, and an earlier cold period between the 4th and 6th centuries. In addition, temperatures varied from region to region across the plateau. A warm period from AD 800 to 1100 in the northeastern Tibetan Plateau was contemporaneous with cooling in the southern Tibetan Plateau, which experienced warming between AD 1150 and 1400. Large-scale trends in the temperature history from the northeastern Tibetan Plateau resemble those in eastern China more than the trends from the southern Plateau. The most notable similarities between the temperature variations of the Tibetan Plateau and eastern China are cold phases during AD 1100–1150, 1500–1550, 1650–1700 and 1800–1850.

Last glaciation and maximum glaciation in the Qinghai-Xizang (Tibet) Plateau: A controversy to M. Kuhle’s ice sheet hypothesis

Since the late 1950’s, many Chinese scientists have explored the remains of the Quaternary glaciation in the Qinghai-Xizang (Tibet) Plateau and its surrounding mountains. In the main, 3–4 glaciations have been recognized. The largest one occurred in the Late Middle Pleistocene with piedmont glaciers, ice caps and trellis valley glaciers in many high peak regions. But here is no evidence of a unified ice sheet covering the whole plateau as described by M. Kuhle. Due to the further uplifting of the Himalayas and Qinghai-Xizang Plateau the climate became progressively driver, diminishing the extension of glaciers during the Late Pleistocene. The elevation of the snow line during the Last Glaciation was about 4,000 m on the south, east and northeast edges of the plateau and ascended to 5500 m on the hinder northwest of the plateau. The thermal effect of the big plateau massif, the sharp increase of aridity from the southeast rim to the northwest inland area and the abrupt decrease of precipitation during the Ice Age largely account for the distribution of the Quaternary glaciers in the Qinghai-Xizang Plateau. The neglect of Chinese literature may be one of the causes accounting for M. Kuhle’s misinterpretation on the environment of the Quaternary glaciations in the Qinghai-Xizang Plateau.Since the late 1950’s, many Chinese scientists have explored the remains of the Quaternary glaciation in the Qinghai-Xizang (Tibet) Plateau and its surrounding mountains. In the main, 3–4 glaciations have been recognized. The largest one occurred in the Late Middle Pleistocene with piedmont glaciers, ice caps and trellis valley glaciers in many high peak regions. But here is no evidence of a unified ice sheet covering the whole plateau as described by M. Kuhle. Due to the further uplifting of the Himalayas and Qinghai-Xizang Plateau the climate became progressively driver, diminishing the extension of glaciers during the Late Pleistocene. The elevation of the snow line during the Last Glaciation was about 4,000 m on the south, east and northeast edges of the plateau and ascended to 5500 m on the hinder northwest of the plateau. The thermal effect of the big plateau massif, the sharp increase of aridity from the southeast rim to the northwest inland area and the abrupt decrease of precipitation during the Ice Age largely account for the distribution of the Quaternary glaciers in the Qinghai-Xizang Plateau. The neglect of Chinese literature may be one of the causes accounting for M. Kuhle’s misinterpretation on the environment of the Quaternary glaciations in the Qinghai-Xizang Plateau.

Impact of urban expansion on regional temperature change in the Yangtze River Delta

Based on non-radiance-calibrated DMSP/OLS nighttime light imagery from 1992 to 2003, urban land area statistical data, meteorological data and land surface temperature data retrieved by MODIS and NOAA/AVHRR data, the influence of urbanization on regional climatic trend of temperature in the Yangtze River Delta (YRD) was analyzed. Conclusions are as follows: 1) There is a significant urbanization process from 1992 to 2003 in the YRD. Four city clusters of Nanjing-Zhenjiang-Yangzhou, Suzhou-Wuxi-Changzhou, Shanghai and Hangzhou Bay form a zigzag city belt. The increase rate of annual mean air temperature in city-belt is 0.28–0.44°C/10a from 1991 to 2005, which is far larger than that of non-city-belt. 2) The urban heat island (UHI) effect on regional mean air temperature in different seasons is summer>autumn>spring>winter. 3) The UHI intensity and the urban total population logarithm are creditably correlated. 4) The UHI effect made the regional annual mean air temperature increased 0.072°C from 1961 to 2005, of which 0.047°C from 1991 to 2005, and the annual maximum air temperature increased 0.162°C, of which 0.083°C from 1991 to 2005. All these indicating that the urban expansion in the YRD from 1991 to 2005 may be regarded as a serious climate signal.

Features, Impacts and Causes of the High Temperature and Large Precipitation Event in the Tibetan Plateau and Its Adjacent Area During 40-30kaBP

Based on records of the Guliya Ice Core (35.6°N,80.5°E),pollen and high lake levels in the Tibetan Plateau and its adjacent area, there appeared a particular warm and wet stage with the mean temperature 2-4℃ higher and large precipitation much more than that of the present. The reconstructed precipitations with Kutzbachs water and energy balance model of closed lake basin are estimated up to 640mm, 560mm and 260mm in the Qinghai Lake, Chabyer Caka/Laguo Co, and Akesaiyi/Tianshuihai Lake, which are 1.7, 3, 5 times of that in the present respectively. The large precipitation, extended to the north slope of Qilian Mountains at the north, and to Yunnan Province at the south east of Qinghai Xizang plateau, had played an important role in the geomorphological evolution of some rivers originated from the Tibetan Plateau. The upstream river pattern of the Yellow River, same as present, had come into being for the Zoige Palaeolake overflowing to meet the headward erosion of the Yellow River in the borderland of Gansu and Sichuan Provinces. The formation of the deep channels with their bottom lower than present sea level in the Three Gorge area, in the middle reach of the Yangtze River, might be related to high speed flood resulted from the upstream large precipitation in the Tibetan Plateau. While flood currents were narrowish and hindered in the gorge channel, the high energy turbulent flow carried large quantitative gravels to cut the river bottom and formed the deep channels (formed before 40kaBP). Some 14 C dates of the buried woods between 40-30kaBP, in the gravel deposits at the channel bottom indicated the upper mechanism process. Some separated closed lake catchments in the Tibetan Plateau, such as, Serling Co, Nam Co and Pangkog Co, were merged into a great closed catchment by water overflow. This high lake level event is mainly caused by the particularly strong Indian monsoon for enhanced cross equator aircurrent from south hemiphere over Indian Ocean activated by high solar radiation of precession cycle in low latitude. On the other hand, we infer, in the period between the event H4 (35.5kaBP) and H3(28-27kaBP), the southward shifted westerlies, from the warm North Atlantic Ocean for northern Eurasia ice sheet gave passive impact on high lake levels for arousing much precipitation.

Temperature estimation by oxygen-stable record over the past 200 ka in Zoige basin

According to the evolutionary processes of stable oxygen isotope in lake water, a physical model has been established to calculate paleotemperature and used to quantitatively re-build the temperature sequences in the past 200 ka in Zoigê basin, eastern Tibet. The results show that in the Zoigê region the maximum temperature of the period equivalent to stage 7 in deep-sea stable oxygen record was 2.7êC higher than that of the present; in stage 6, it was 4.3êC lower and the value of the peak temperature of stage 5 was 5.2 êC higher than the present air temperature; in stage 4, the average temperature was 2-3êC lower; in stage 3, the curve of the temperature es-timated displayed the character of two peaks and one valley, and the value of the temperature dif-ference in the period was above 4êC. Moreover, by comparing the tendency of the curves of pa-leotemperature calculated and responsive stable oxygen isotope of authicarbonate, we also found that during stage 6 the environment in the Zoigê basin was extraordinary, inferring that the stage represented a transition period from warm-dry and cold-wet to warm-wet and cold-dry.According to the evolutionary processes of stable oxygen isotope in lake water, a physical model has been established to calculate paleotemperature and used to quantitatively rebuild the temperature sequences in the past 200 ka in Zoige basin, eastern Tibet. The results show that in the Zoige region the maximum temperature of the period equivalent to stage 7 in deep-sea stable oxygen record was 2.7℃ higher than that of the present; in stage 6, it was 4.3℃ lower and the value of the peak temperature of stage 5 was 5.2℃ higher than the present air temperature; in stage 4, the average temperature was 2-3℃ lower; in stage 3, the curve of the temperature estimated displayed the character of two peaks and one valley, and the value of the temperature difference in the period was above 4℃. Moreover, by comparing the tendency of the curves of paleotemperature calculated and responsive stable oxygen isotope of authicarbonate, we also found that during stage 6 the environment in the Zoige basin was extraordinary, inferring that the stage represented a transition period from warm-dry and cold-wet to warm-wet and cold-dry.

The isotopic record at an alpine glacier and its implications for local climatic changes and isotopic homogenization processes

Stratigraphic variations of oxygen isotopes in the snow which accumulates during the winter at the Norwegian glacier Austre Okstindbreen are not entirely eliminated after 1- 2 months of ablation in the following summer. The relationship between regional temperature changes and δ 18 O values in the snowpack is affected by many natural factors, but 1989/90 winter air temperatures were reflected in the snow which remained on Austre Okstindbreen at 1350 m a.s.l. in July 1990. There were many variations of δ 18 O values in the 4.1 m of snow above the 1989 summer surface, but variations in the underlying firn were relatively small. Meltwater percolation modifies the initial variations of δ 18 O values in the snowpack. At a site below the mean equilibrium-line altitude on Austre Okstindbreen, increased isotopic homogenization within a 10 day period in July accompanied an increase of the mean δ 18 O value. Although the isotopic record at a temperate glacier is likely to be influenced by more factors than is that at polar glaciers, it can provide an estimate of the approximate trend of local temperature variations.

Paleo-environmental changes in the Yangtze Delta during past 8000 years

The Yangtze Delta is one of the economically most developed areas in China. It is located in the eastern China monsoon region. Archaeological excavations and environment-archaeology studies over many years in this region provide exceptional information about climate changes, development of human civilization and also human-environment interactions. Archaeological excavations made in the study region reveal that the development of Neolithic cultures is not continuous, which may be a result of extreme climatic events. The analysis of14C-dated buried paleotrees, peat and shell ridges show the rise and fall of human civilization in the study area. The research results presented in this paper confirm that human civilization collapsed six times in the Yangtze Delta, matching six high sea level epoches, peat accumulation and buried paleotrees formation periods respectively. This indicates that human activities in the Yangtze Delta are controlled by local climate changes and changing hydrological conditions. The collapse of the Liangzhu culture (5000 aBP-3800 aBP) in about 4000 aBP, after a tremendous flooding event, followed by a relatively backward Maqiao culture (3800 aBP-3200 aBP) confused researchers and aroused their great interest. The research results in this paper show that the collapse of the Liangzhu culture is a result of several factors, for example war and food shortage, but the flooding event occurred in the late Liangzhu culture epoch is the main factor therein.The Yangtze Delta is one of the economically most developed areas in China. It is located in the eastern China monsoon region. Archaeological excavations and environment-archaeology studies over many years in this region provide exceptional information about climate changes, development of human civilization and also human-environment interactions. Archaeological excavations made in the study region reveal that the development of Neolithic cultures is not continuous, which may be a result of extreme climatic events. The analysis of14C-dated buried paleotrees, peat and shell ridges show the rise and fall of human civilization in the study area. The research results presented in this paper confirm that human civilization collapsed six times in the Yangtze Delta, matching six high sea level epoches, peat accumulation and buried paleotrees formation periods respectively. This indicates that human activities in the Yangtze Delta are controlled by local climate changes and changing hydrological conditions. The collapse of the Liangzhu culture (5000 aBP-3800 aBP) in about 4000 aBP, after a tremendous flooding event, followed by a relatively backward Maqiao culture (3800 aBP-3200 aBP) confused researchers and aroused their great interest. The research results in this paper show that the collapse of the Liangzhu culture is a result of several factors, for example war and food shortage, but the flooding event occurred in the late Liangzhu culture epoch is the main factor therein.

The quaternary climo-environment changes in Chaiwopu basin of Xinjiang region

This paper describes the paleoclimatic changesoccurring in the Chaiwopu Basin since 730,000 yr.B.P., together with theformation and evolution of Chaiwopu Lake based on the chronology and characteristics of a core drilled in the basin. Analysis of the drilling core provides information on the climate and environment of the area. It would appear that the paleoclimatic changes that occurred in the basin during the Pleistocene was controlled by the relationship between the sun and the earth and by Long-term (10,000 yr.) climatic cycles. The climate tended to cold-dry during the glacial period (ice age) and warm-moist during the interglacial. Following the warm period of the Holocene, short-term (1,000 yr.) climatic cycles occurred in cool-moist periods, similar to the “Little Ice Age”, alternated with warm-dry periods.This paper describes the paleoclimatic changesoccurring in the Chaiwopu Basin since 730,000 yr.B.P., together with theformation and evolution of Chaiwopu Lake based on the chronology and characteristics of a core drilled in the basin. Analysis of the drilling core provides information on the climate and environment of the area. It would appear that the paleoclimatic changes that occurred in the basin during the Pleistocene was controlled by the relationship between the sun and the earth and by Long-term (10,000 yr.) climatic cycles. The climate tended to cold-dry during the glacial period (ice age) and warm-moist during the interglacial. Following the warm period of the Holocene, short-term (1,000 yr.) climatic cycles occurred in cool-moist periods, similar to the “Little Ice Age”, alternated with warm-dry periods.