Historical Climate Changes of the West China in the Holocene

Based on the results of palaeoclimate studies on glaciers,geology,deserts,lakes,tree rings and historical documents etc,the sequences of climate changes since the holocene in the west China are given in this paper.The main results are as follows:1.The climate changes of the Holocene can be divided into three stages.The transition from the middle Holocene to the late Holocene might occur before 3500 years,which were 500 years earlier than that of the East China.Abrupt changes during the transitional period are also found.2.The climatical oscillations in a thousand-year-scale has experienced six cold stages and five warm stages since the beginning of Holocene,The cold stages were 8700a.B.P, 5900-5400a.B.P,4200-3800a.B.P,3000-2700a.B.P,2000-1400a.B.P,1000a.B.P,the present;and the warm stages were 7500-5900a.B.P,5400-4200a.B.P, 3800-3000a.B.P,2700-2000a.B.P,1400-1000a.B.P respectively.The climatical oscillation had a period of 1000-3000 years in a thousand-year-scale.3.In the recent 1000 years,the temperature change of the climatical oscillations in a hundred-year-scale has experienced six low temperature stages and five high temperature stages.The former were A.D.1100's,1310's,1480's,1830's,1950's.and the later were A.D.1220's, 1390's, 1570's, 1780's, 1990's, respectively.The pcriod of changes was 120-210 years.The coldest stage appeared from the middle 17th century to the early 18th century.For the past 500 years.the drought phase with the highest frequency appeared in A.D.1480-1650,and three most severe drought events 18th century.In the recent 100 years,there is a dry-tendency in the eastern parts of the Northwest China and the North China.