Long-term summer temperature variations in the Pyrenees from detrended stable carbon isotopes

Abstract

Substantial effort has recently been put into the development of climate reconstructions from tree-ring stable carbon isotopes, though the interpretation of long-term trends retained in such timeseries remains challenging. Here we use detrended δ<sup>13</sup>C measurements in Pinus uncinata tree-rings, from the Spanish Pyrenees, to reconstruct decadal variations in summer temperature back to the 13<sup>th</sup> century. The June-August temperature signal of this reconstruction is attributed using decadally as well as annually resolved, 20<sup>th</sup> century δ<sup>13</sup>C data. Results indicate that late 20<sup>th</sup> century warming has not been unique within the context of the past 750 years. Our reconstruction contains greater am-plitude than previous reconstructions derived from traditional tree-ring density data, and describes particularly cool conditions during the late 19<sup>th</sup> century. Some of these differences, including early warm periods in the 14<sup>th</sup> and 17<sup>th</sup> centuries, have been retained via δ<sup>13</sup>C timeseries detrending - a novel approach in tree-ring stable isotope chronology development. The overall reduced variance in earlier studies points to an underestimation of pre-instrumental summer temperature variability de-rived from traditional tree-ring parameters.