Limited early-industrial warming and strong volcanic imprints in the Caucasus: the first temperature reconstruction based on maximum latewood density

Abstract

The Caucasus occupies a unique climatic region influenced by European, Mediterranean, and Asian circulation systems, yet it remains underrepresented in tree ring-based Northern Hemisphere temperature proxy networks. Here, we present the first summer temperature reconstruction for the Caucasus region based on maximum latewood density (MXD). We used X-ray micro-computed tomography of tree-ring samples from Pinus sylvestris growing at the upper tree line in the Lesser Caucasus and an ensemble nested regression approach to develop a robust 326 year-long June-September temperature reconstruction (1697-2022). The record explains - regionally unprecedented - 72 % of temperature variance during the instrumental period (1901-2022) and captures distinct interannual and multi-decadal variability including pronounced warming since the 1990s and a strong imprint of major volcanic eruptions. Temperatures in the second half of the 19th century were not significantly colder in the Caucasus than in the second half of the 20th century. The reconstruction highlights the exceptional magnitude and pace of 21st century warming in the region, which is without analogue at least in the past three centuries. Comparison with regional and large-scale temperature reconstructions reveals strong agreement within the Caucasus but negative correlations with Central Europe, indicating distinct temperature variability patterns across Europe and western Asia. Future work should focus on the climate dynamics behind this dipole and the extension of temperature-sensitive tree-ring records in the region.