Comment on “Absence of Age‐Related Trends in Stable Oxygen Isotope Ratios From Oak Tree Rings” by Duffy et al. (2019)

Abstract

AbstractDuffy et al. (2019, https://doi.org/10.1029/2019GB006195) assess age‐related trends in tree‐ring oxygen isotope (δ18O) series from the UK using two approaches. They argue that their conventional approach, which also forms the basis for the frequently used Regional Curve Standardization (RCS) method, is incapable of identifying age‐related trends and that detrending the data would distort climatic indications. However, their study disregards much of the existing dendrochronological literature essential also for their trend detection approaches. Here, we reanalyze the data from their supplementary item and show that detrending δ18O series using the RCS method does not remove long‐term trends—indicative of summertime drying in England and Wales—and that the data set used in Duffy et al. (2019) is likely too small to draw wider implications.