Assessment of whether tree-ring hydroclimate reconstructions are useful for characterising extreme drought in East Anglia (England)

Region East of England Focus Paleoclimate proxies are used here to characterise extreme droughts including those corresponding to a 1:500-year return period. We evaluate four tree-ring hydroclimate (precipitation or drought index) reconstructions representing similar geographical regions across East Anglia and Southern England. New hydrological insights The overall agreement between the reconstructions is found to be weak or moderate, partly due to their differing seasons, regions and methodological differences. Therefore, we used all four reconstructions to quantify the sensitivity of drought to choice of reconstruction. We show that reconstruction errors influence the quantification of extreme dry seasons (here spring/summer seasons) and must be accounted for in the analysis especially if the reconstruction was calibrated using regression. We demonstrate that modelling the reconstruction error as a random term, as well as z-score standardisation, enables the reconstruction to reproduce instrumental climate behaviour such as the rank-order drought curve. Using these approaches, we quantify the occurrence probability of high threshold extreme events and evaluate the differences in severity of droughts across the reconstruction datasets (which vary in length from 800 to 1112 years). We conclude that tree-ring reconstructions can provide valuable long term hydroclimate insight, but they should be used with caution when investigating extreme droughts due to inter-reconstruction differences and the need to represent reconstruction errors.