Annual temperature history in Southwest Tibet during the last 400 years recorded by tree rings

We present a tree ring-width record from the southern Tibetan Plateau (TP) which spans from 1612-1998 AD (387 years). The series was developed from Tibetan juniper (Juniperus tibetica Kom) growing at sites near the western distribution limit of the species. Two versions of the chronology, a traditionally standardized chronology (TSC) and a regional curve standardization (RCS)chronology were developed. Linear regression models between ring width and mean annual temperature account for 41% (TSC) and 43% (RCS) of the annual (July June) temperature variance for the period 1957-1998. According to the TSC reconstruction, warm periods occurred during the 1620s, 1650-1675, 1720s, 1740-1790, 1810s, 1850s-1890s, 1935-1950, and 1957-1964 and since 1980. Cold conditions prevailed during the 1630s-1640s, 1680s-1710s, 1730s, 1820-1840s, 1900s-1920s and the 1970s. Within the last 400 years, the late-20th century warming is distinctive but still within the range of natural climatic variability of this region. Comparison of our TSC reconstruction with proxy temperature records from other parts of the TP shows that the cold conditions during the 1730s, 1900s-1920s, and 1970s, and the warm periods during the 1770-1800, 1850s-1890s, 1935-1950, and 1957-1964 and since 1980 were synchronously occurring broad-scale climate anomalies on the whole TP. Differences between the reconstructions are found during the 17th century and around 1760, which were probably caused by local differences in temperature change and different sensitivity in seasonality. The RCS series portrays low-frequency variations such as warm periods during 1620-1640, 1650-1690, 1715-1790, and 1845-1875, and cold conditions during 1640-1650, 1690-1715, and 1875-1995. These long-term trends need to be verified by developing other proxy records that target to capture low-frequency signals in the future. Copyright (C) 2009 Royal Meteorological Society