Strong volcanic imprints contrast with a mild Little Ice Age: a first temperature reconstruction based on maximum latewood density from the Caucasus

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 18^th and 19^th century, a period often described as the Little Ice Age, were not significantly colder in the Caucasus than in the first half of the 20^th century. The reconstruction highlights the exceptional magnitude and persistence of 21^st 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.