Reconstructed annual mean temperatures for the northeastern margin of the Tibetan Plateau: associations with the East Asian monsoons and volcanic events

Abstract

Owing to a lack of available long-term climatic records, data related to past climatic variability throughout the Tibetan Plateau remains limited. In this study, we found that Qilian juniper tree growth was significantly and positively correlated (p < 0.001) to yearly mean temperatures in the northeastern margin of the Tibetan Plateau. We developed an annual mean temperature reconstruction from year 1740 CE based on growth-climate relationships in the study area. Our reconstruction accounted for 53.9% of total variance from 1956 to 2012 (the calibration period). Through this reconstruction, we were successfully able to capture recent abrupt climate change events that generally agreed with other temperature-sensitive tree-ring reconstructions on both regional and hemisphere scales under a decadal timescale. Periods from 1820 to 1830, 1855 to 1890, and 1960 to 1985 CE corresponded to cold periods in the reconstruction, while the 1740s and periods from 1795 to 1815 and from 1990 to 2012 CE corresponded to relatively warm periods. We also detected increased interannual change variability in annual mean temperatures since the 1980s, which could be related to increasing variability in the East Asian winter monsoon as well as the rapid climate warming that has occurred since this time. From these reconstructed temperatures, we were successfully able to capture the occurrences of large volcanic events in China as well as five historic volcanic events outside China that had global implications on climate variability and that resulted in planetary cooling during the period from 1740 to 2012 CE. This in turn suggested that these volcanic events would have had short-lived impacts (approximately from 1 to 3 years) on temperature variation in the study area. The aim of this study was to provide a perspective in which to explore the mechanisms that simultaneously influence tree rings and climate.

Dendroclimatic Reconstruction of Mean Annual Temperatures over Treeline Regions of Northern Bhutan Himalayas

“…As per Past Global Changes (PAGES) project [15], dendrochronology is considered one of the most useful methodologies to inform about past climate changes because of its annual resolution and absolute dating [15][16][17][18]. To minimize noise in tree-ring data, it is advisable to collect many trees to stabilize the signal of interest, and to use the available state-of-the-art detrending/standardization procedure, prior to using the data for reconstruction purposes [3,16,19,20].…”

“…To minimize noise in tree-ring data, it is advisable to collect many trees to stabilize the signal of interest, and to use the available state-of-the-art detrending/standardization procedure, prior to using the data for reconstruction purposes [3,16,19,20]. However, many regional reconstructions reveal notable variations in amplitude and timing of certain warm and cold periods [2,3,18,[21][22][23][24], and degradation in reconstruction skills from periods of calibration to verification is also of major concern [18,24]. Moreover, existing reconstructions over Himalaya [7][8][9][10][11][12]24,25] lack consistency in targeted climate variables, challenging larger data composites for robust climate trend analysis [7].…”

“…This is unfortunate since the Himalayan region is thought to be more vulnerable and sensitive to climate change, as a higher rate of change is happening here than in many other regions of the world [26,27]. For instance, the warming trend in Eastern Himalayas and Tibetan Plateau is increasingly steeper with increased altitudes [13,14,[28][29][30] as measured over the past 50 years [18].…”

“…The authors concluded that the JJA-TEMR-BT13 skill could be substantially underestimated because of the quality of the local instrumental climate data. However, this conclusion could be insufficient because JJA-TEMR-BT13 did not fully capture well-known large-scale climate events and periods [18].…”

“…The objectives of this study were to explore dendroclimatic signals in tree-ring width chronologies from the tree-ring network, and to reconstruct, if possible, mean annual temperatures over Northern Bhutan, Himalaya. Annual temperatures have rarely been used as predictand (dependent variable) from tree-ring predictors (independent variable), largely because tree growth usually occurs in the summer months [3,5,17,18,24]. In fact, very few reconstructions of annual temperatures exist globally, and if attempted, poor results are often obtained [3,21,37].…”