A dendrochronological analysis of maximum summer half-year temperature variations over the past 700 years on the northeastern Tibetan Plateau

Summary

Three cypress (Juniperus przewalski Kom.) tree ring width chronologies were established based on tree ring cores collected at elevations ranging from 3,550–3,700 m a.s.l. in the headwaters of the Yellow River, Animaqin Mountains, in the northeastern Tibetan Plateau. Statistical analysis showed that the chronologies were negatively correlated to the summer half-year (April to September) maximum air temperature (p < 0.01). The maximum temperature of the summer half-year was reconstructed for the past 700 years based on the developed chronologies. The reconstruction explains 47% of the maximum temperature variance which occurred during the period with meteorological observations (1959–2001). Both cold and warm periods were evident in the reconstructed summer half-year maximum temperature record over the past 700 years. The summer half-year maximum temperature has increased since the 1980s, and the decade 1980 to 1990 is ranked as one of the fastest warming decades on record, however this is not exceptional on centennial or millennial timescales. The ten-year average summer half-year maximum temperature in the 1990s is relatively high, but it is still colder than several other periods, including 1480s–1490s and 1590s–1600s. The 1480s is the warmest period in the past 700 years. The summer half-year maximum temperature can change significantly within decades. From 1490s to 1500s, the temperature dropped 0.89 °C. In the northeastern region of the Tibetan Plateau, warmer periods are often accompanied by drought whereas cold periods are coincident with above average precipitation.