A 622-year regional temperature history of southeast Tibet derived from tree rings

Abstract

A tree ring-width record spanning from AD 1377—1998 was developed from Tibetan juniper ( Cupressus gigantea) growing at sites north of the deep gorge of the Yarlung Tsangbo River of southeast Tibet. A linear regression model between ring width and mean January—June temperature accounts for 35% of January—June temperature variance for the period 1961—1998. Based on this model, we reconstructed January—June temperature variation history for the study region during the past 622 years. Warm conditions occurred during AD 1385—1418, 1443—1466, 1482—1501, 1523—1548, 1570s, 1705—1759, 1770—1790, 1851—1888, 1910s, and 1938—1965, and periods of relatively cold years are identified for AD 1419—1442, 1470s, 1502—1522, 1550—1569, 1610—1640, 1680—1700, 1760s, 1791—1850, 1900s and 1965—1995. Spatial correlation between tree rings and observed temperatures indicates that the reconstruction is representative of temperature change for southeast Tibet. Regional cold conditions during AD 1625, 1685, 1760, 1800—1850, 1890—1930 and 1965—1995, and warm conditions during 1710, 1730—1750, 1850—1890 and 1930—1960 can be identified in the eastern Tibetan Plateau. Our reconstruction shows good agreement with modelled regional temperatures derived from an ECHO-G model simulation. Common cold periods around 1470, 1685 and 1845 corresponding to the Spörer Minimum, the Maunder Minimum and the Dalton Minimum periods of low solar activity and increased volcanic activity were identified, indicating that solar and volcanic activity played an important role in temperature change of this region. The discrepancy between modelled and reconstructed temperatures was noted around 1965, reflecting that temperature decrease in the late 20th century (1965—1995) is anomalous.