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Two sediment cores recovered in the central part of Daihai Lake in north-central China were analysed at 2-to 4-cm intervals for total inorganic and organic carbon (TIC and TOC) concentrations. The TIC concentration is inferred to reflect temperatures over the lake region and an increase in the TIC concentration implies an increase in the temperature. TOC concentration is considered to reflect the precipitation in the lake basin and higher TOC concentrations denote more precipitations. Thus AMS 14C time series of the TIC and TOC records of Daihai Lake sediments uncovers a detailed history of changes in temperature and precipitation in north-central China during the last c. 12 000 yr. The Holocene, an epoch of postglacial warmth, started c. 11 500 cal. yr BP, and can be subdivided into three stages: the early (c. 11 500-8100 cal. yr BP), middle (c. 8100-3300 cal. yr BP) and the late Holocene (c. 3300-0 cal. yr BP). The climate was warm and dry during the early Holocene, warm and wet during the middle Holocene, and in the late Holocene became cooler and drier but displayed a relatively warmer and wetter interval between c. 1700 and 1300 cal. yr BP. The Holocene Climatic Optimum, defined as a postglacial episode of both megathermal and megahumid climate, might have occurred in north-central China between c. 8100 and 3300 cal. yr BP, and the climate during this period was variable and punctuated by cool and/or dry events. We infer that changes in the temperature were directly controlled by changes in summer solar radiation in the Northern Hemisphere resulting from progressive changes in the Earth's orbital parameters. Whereas an increase in the monsoonal precipitation could be closely related to an increase in the sea surface temperature of the low-latitude Pacific Ocean, an increase in the temperature and size of the Western Pacific Warm Pool and a westward shifted and strengthened Kuroshio Current in the western Pacific.

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Eolian quartz flux (EQF, g cm−2(103 yr)−1) to Lake Biwa, central Japan, provides direct information on variations of the East Asian winter monsoon. Lake Biwa sediments spanning the past ca. 145,000 yr are characterized by two main periods when EQF values were significantly greater than 5.50 g cm−2(103 yr)−1, and two main intervals during which EQF values were lower. Two periods with EQF values >5.50 g cm−2(103 yr)−1occurred from ca. 145,000 to 125,000 and 73,000 to 13,000 yr B.P., while times of lower EQF values occurred from ca. 125,000 to 73,000 yr B.P. and around ca. 5500 yr B.P. Between ca. 125,000 and 73,000 yr B.P., three minimum EQF values and two intervening peaks of slightly higher EQF values are recorded. EQF increased markedly from ca. 73,000 to 13,000 yr B.P., whereas between ca. 53,000 and 20,000 yr B.P. the values recorded were relatively lower than those recorded during either the preceding or the subsequent episodes. The data imply that the East Asian winter monsoon strengthened during the periods when EQF values were high, and weakened during the intervals with low EQF values. The EQF record of Lake Biwa can be correlated with the grain-size record of the quartz fraction in Chinese loess and with the SPECMAP marine δ18O record. However, the EQF record apparently lags ca. 5000 yr behind the loess and δ18O records during stage 6/5 and 2/1 transitions and ca. 10,000 yr during stage 5/4 transition. These apparent lags could be due to problems with the chronology; alternatively, they may imply that the eolian quartz flux depended more on the extent of dust source regions than on wind intensity during these transitions.

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