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Reconstructing of past hydroclimates at regional scales during the Common Era (CE) is necessary to place the current warming in the context of natural climate variability. Here we present a composite record of oxygen isotope variations during last 2500 years based on eight stalagmites from four caves in the central Pyrenees (NE Spain) dominated by temperature variations, with the amount of precipitation playing a minor role. The dataset is compared with other Iberian reconstructions that show a high degree of internal coherence with respect to variability at the centennial scale. The Roman Period (RP) (especially 0–200 CE), the Medieval Climate Anomaly (MCA), and part of the Little Ice Age (LIA) represent the warmest periods, while the coldest decades occurred during the Dark Ages (DA) and most of the LIA intervals (e.g., 520–550 CE and 1800–1850 CE). Importantly, the LIA cooling or the MCA warming were not continuous or uniform and exhibited high decadal variability. The Industrial Era (IE) shows an overall warming trend although with marked cycles and partial stabilization during the last 2 decades (1990–2010). The strong coherence between the speleothem data, European temperature reconstructions and global tree-ring data informs about the regional representativeness of this new record as Pyrenean past climate variations. Solar variability, likely through its impact on the North Atlantic Oscillation, and major volcanic eruptions appear to be the two main drivers of climate in southwestern Europe during the past 2.5 millennia. [ABSTRACT FROM AUTHOR]

Tree lines are supposed to react sensitively to the current global change. However, the lack of a long‐term (millennial) perspective on tree line shifts in the Pyrenees prevents understanding the underlying ecosystem dynamics and processes.We combine multiproxy palaeoecological analyses (fossil pollen, spores, conifer stomata, plant macrofossils, and ordination) from an outstanding ice cave deposit located in the alpine belt c. 200 m above current tree line (Armeña‐A294 Ice Cave, 2,238 m a.s.l.), to assess for the first time in the Pyrenees, tree line dynamics, and ecosystem resilience to climate changes 5,700–2,200 (cal.) years ago.The tree line ecotone was located at the cave altitude from 5,700 to 4,650 cal year bp, when vegetation consisted of open Pinus uncinata Ramond ex DC and Betula spp. Woodlands and timberline were very close to the site. Subsequently, tree line slightly raised and timberline reached the ice cave altitude, exceeding its today's uppermost limit by c. 300–400 m during more than four centuries (4,650 and 4,200 cal year bp) at the end of the Holocene Thermal Maximum. After 4,200 cal year bp, alpine tundra communities dominated by Dryas octopetala L. expanded while tree line descended, most likely as a consequence of the Neoglacial cooling. Prehistoric livestock raising likely reinforced climate cooling impacts at 3,450–3,250 cal year bp. Finally, a tree line ecotone developed around the cave that was on its turn replaced by alpine communities during the past 2,000 years.Synthesis. The long‐term Pyrenean tree line ecotone sensitivity suggests that rising temperatures will trigger future P. uncinata and Betula expansions to higher elevations, replacing arctic–alpine plant species. Climate change is causing the rapid melting of the cave ice; rescue investigations would be urgently needed to exploit its unique ecological information. We present the first millennial to centennial scale reconstruction of tree line dynamics for the Pyrenees. Our inferences are based on biological proxies (fossil pollen, plant macrofossils, and stomata) found in a unique palaeoenvironmental archive: an ice cave deposit discovered 200 m above current tree line. One main outcome is that subalpine forests were generally more widely distributed during the last 5,700 years and subalpine–alpine vegetation responded sensitively to both climate changes and human activities. Editor's Choice [ABSTRACT FROM AUTHOR]

The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I). [ABSTRACT FROM AUTHOR]