Updating historical tree-ring records for climate reconstruction

Over the past three decades, numerous Late Holocene-long tree-ring (TR) chronologies have been developed for different parts of Europe that allow archaeological, historical and cultural wood remains to be dated with annual precision. Ironically, palaeoclimatic evidence inherent in such composites is limited as modern updates essential for calibration/verification with instrumental measurements are often inappropriate, incomplete or even missing. Here we proposes a novel approach to updating historical TR records while preventing statistical over-fit with the target data and advocate 'horizontal' splitting between historical (early) and recent (modern) TR samples prior to their standardization (detrending). This split-technique will help to overcoming unprecedented effects of increased atmospheric greenhouse-gas, biospheric fertilization, forest management, sample replication, age-structure and chronology development associated with modern proxy updates. (C) 2010 Elsevier Ltd. All rights reserved.