Tree-Ring-Width Chronologies from Moisture Stressed Sites Fail to Capture Volcanic Eruption Associated Extreme Low Temperature Events

Tree-rings have been extensively used to develop temperature reconstructions using conifer species growing in different parts of the Himalaya. The reconstructions are based on the existence of both positive and negative relationship between the tree-ring chronologies and instrumental temperature records. However, the reconstructions based on positive relationship between tree-ring and temperature series are few. Regional temperature reconstructions developed using tree-ring series have revealed a significant correlation with the regional data which degraded gradually with distance from the tree-ring sampling sites indicating dominant orographic control on climate. On critical assessment of the available tree-ring-based temperature reconstructions, glaring anomalies were reported especially in case of the extreme years coinciding with the volcanic eruption associated cooling. Tree-ring-based reconstructions from Kashmir and Nepal, where temperature has direct forcing on tree-ring widths, indicated unusually cold temperatures in 1816, coinciding with the Tambora volcanic eruption in April 1815 in Indonesia. However, in the case of the chronologies having negative relationship with temperature, usually warmer conditions are reconstructed against the narrow rings usually observed in 1816. The narrow rings in 1816 could have been caused due to volcanic eruption induced cooling as well as reduced solar radiation restricting the photosynthesis. Thus changes in the limiting factor led to the break in relationship between tree-ring indices and climate parameters. In view of this, it is suggested that the environmental variables having direct relationship with tree growth should be reconstructed from tree-ring chronologies as there exists a fair possibility that the growth limiting factor such as temperature remains stable over time.