Recent  

Bark beetle outbreaks are important disturbances to Norway spruce forests. Their meteorological and climatological triggers are analysed for the main oubreaks over the territory of the Czech Republic based on newly created series of such outbreaks, covering the 1781–2021 CE period. The paper demonstrates the shift from windstorms as the main meteorological triggers of past outbreaks to effects of high temperatures and droughts together with windstorms in past decades.

The spring onset and growing season dynamics during the Late Glacial period in the Baltic region were reconstructed using the micro-phenology based on dwarf birch subfossil leaf cuticles. The comparison of pollen- and chironomid-inferred past temperature estimations with spring onset, growth degree day, and plant macrofossil data shows coherent patterns during the cooler Older Dryas and warmer Bølling–Allerød periods but more complicated climate dynamics during the Younger Dryas cold reversal.

Some 155 million years ago, sediments were deposited in a shallow subtropical sea. Coral reefs formed in a warm and arid climate during high sea level, and clays were washed into the ocean at low sea level and when it rained. Climate and sea level changes were induced by cyclical insolation changes. Analysing the sedimentary record, it appears that sea level rise today (as a result of global warming) is more than 10 times faster than the fastest rise reconstructed from the geologic past.

Using statistical tree-growth proxy system models in the data assimilation framework may have limitations. In this study, we successfully incorporate the process-based dendroclimatic model MAIDEN into a data assimilation procedure to robustly compare the outputs of an Earth system model with tree-ring width observations. Important steps are made to demonstrate that using MAIDEN as a proxy system model is a promising way to improve large-scale climate reconstructions with data assimilation.

Tree-ring data and written sources from northern Fennoscandia reveal that large 17th century eruptions had considerable climatic, agricultural, and socioeconomic impacts far away from the eruption locations. Yet, micro-regional investigation shows that the human consequences were commonly indirect, as various factors, like agro-ecosystems, resource availability, institutions, and personal networks, dictated how the volcanic cold pulses and related crop failures materialized on a societal level.

We present a new and highly resolved atmospheric CO₂ record from the Siple Dome ice core, Antarctica, over the early Holocene (11.7–7.4 ka). Atmospheric CO₂ decreased by ~10 ppm from 10.9 to 7.3 ka, but the decrease was punctuated by local minima at 11.1, 10.1, 9.1, and 8.3 ka. We found millennial CO₂ variability of 2–6 ppm, and the millennial CO₂ variations correlate with proxies for solar forcing and local climate in the Southern Ocean, North Atlantic, and eastern equatorial Pacific.

Major volcanic eruptions are known to cause considerable short-term impacts on the global climate. Their influence on long-term climate variability and regime shifts is less well-understood. Here we show that very large, bipolar eruptions occurred more frequently than expected by chance just before abrupt climate change events in the last glacial period (Dansgaard–Oeschger events). Thus, such large eruptions may in some cases act as short-term triggers for abrupt regime shifts of the climate.

We evaluated the South American Summer Monsoon over the last millennium and dynamically interpreted the principal modes of variability. We find the spatial patterns of the monsoon are an intrinsic feature of the climate modulated by external forcings. Multi-centennial mean state departures during the Medieval Climate Anomaly and Little Ice Age show regionally coherent patterns of hydroclimatic change in both a multi-archive network of oxygen isotope records and isotope-enabled climate models.

At the end of the Cretaceous period, massive volcanism in India emitted enough carbon dioxide into the atmosphere to warm the climate globally above an already warm background state. We reconstruct late Cretaceous seawater temperatures much warmer than today using the chemistry of fossil oysters from the modern-day Netherlands and Belgium. Covariations in temperature and water chemistry indicate changing ocean circulation patterns, potentially related to fluctuating sea level in this region.

With a comprehensive Earth-system model including the global carbon cycle, we simulated the climate state during the last glacial maximum. We demonstrated that the CO₂ concentration in the atmosphere both in the modern (pre-industrial) age (~280 ppm) and in the glacial age (~190 ppm) can be reproduced by the model with a common configuration by giving reasonable model forcing and total ocean inventories of carbon and other biogeochemical matter for the respective ages.

We provide simple quantitative models for the interglacial and glacial intensities over the last 800 000 years. Our results suggest that the memory of previous climate states and the time course of the insolation in both hemispheres are crucial for understanding interglacial and glacial intensities. In our model, the shift in interglacial intensities at the Mid-Brunhes Event (~430 ka) is ultimately attributed to the amplitude modulation of obliquity.

The TEX₈₆ proxy is often used by paleoceanographers to reconstruct past sea-surface temperatures. However, the origin of the TEX₈₆ signal in marine sediments has been debated since the proxy was first proposed. In our paper, we show that TEX₈₆ carries a mixed sea-surface and subsurface temperature signal and should be calibrated accordingly. Using our 15-million-year record, we subsequently show how a TEX₈₆ subsurface temperature record can be used to inform us on past sea-surface temperatures.

The investigation of a 9 m long sediment core recovered at ca. 300 m water depth demonstrates that cold-water coral mound build-up within the East Melilla Coral Province (southeastern Alboran Sea) took place during both interglacial and glacial periods. Based on the combination of different analytical methods (e.g. radiometric dating, micropaleontology), we propose that corals never thrived but rather developed under stressful environmental conditions.

Using an Earth system model of intermediate complexity, we quantify contributions of the Earth's orbit, greenhouse gases (GHGs) and ice sheets to the strength of Saharan greening during late Quaternary African humid periods (AHPs). Orbital forcing is found as the dominant factor, having a critical threshold and accounting for most of the changes in the vegetation response. However, results suggest that GHGs may influence the orbital threshold and thus may play a pivotal role for future AHPs.

We have created a new global surface temperature reconstruction of the climate of the Last Glacial Maximum, representing the period 19–23 000 years before the present day. We find that the globally averaged mean temperature was roughly 4.5 °C colder than it was in pre-industrial times, albeit there is significant uncertainty on this value.

This research contributes to efforts solving research questions related to the history of ice sheet decay in the Northern Hemisphere. The East Siberian continental margin sediments provide ideal material for identifying the mineralogical signature of ice sheet derived material. Heavy mineral analysis from marine glacial sediments from the De Long Trough and Lomonosov Ridge was used in interpreting the activity of the East Siberian Ice Sheet in the Arctic region.

We examined annually resolved stable carbon and hydrogen isotope ratios of wood lignin methoxy groups of beech trees growing in temperate, low elevation environments. Here, carbon isotope ratios reveal highest correlations with regional summer temperatures while hydrogen isotope ratios correlate more strongly with large-scale temperature changes. By combining the dual isotope ratios of wood lignin methoxy groups, a proxy for regional- to subcontinental-scale temperature patterns can be applied.

Algae preserved in seafloor sediments have allowed us to reconstruct how Antarctic sea ice has varied between cold and warm time periods in the last 130 000 years. The patterns and timings of sea-ice increase and decrease vary between different parts of the Southern Ocean. Sea ice is most sensitive to changing climate at the external edges of Southern Ocean gyres (large areas of rotating ocean currents).

The WACSWAIN project (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) investigates the fate of the West Antarctic Ice Sheet during the last warm period on Earth (115 000–130 000 years before present). Within this framework an ice core was recently drilled at Skytrain Ice Rise. In this study we present a stratigraphic chronology of that ice core based on absolute age markers and annual layer counting for the last 2000 years.

We present sedimentary redox-sensitive trace metal records from five sediment cores retrieved from the SW Indian Ocean. These records are indicative of oxygen-depleted conditions during cold periods and enhanced oxygenation during interstadials. Our results thus suggest that deep-ocean oxygenation changes were mainly controlled by ocean ventilation and that a generally more sluggish circulation contributed to sequestering remineralized carbon away from the atmosphere during glacial periods.

We provide high-resolution Cd / Ca records of benthic foraminifera on two cores from the northern Indian Ocean since the last deglaciation. We reconstructed intermediate Cd_w records based on Cd / Ca. Combined with benthic foraminiferal assemblages, we show that intermediate Cd_w during the last deglaciation was mainly influenced by the ventilation of intermediate–bottom water masses. Thereafter during the Holocene surface productivity is the main forcing factor related to monsoon precipitation.

Applying yearly drought and flood records from historical documents and precipitation data in the period of instrumental measurements, this study constructs a time series of extreme droughts and floods in the Hanjiang River Basin from 1426–2017 and analyzes the temporal and spatial characteristics of the extreme drought and flood event variations.

Despite its importance in the global climate, our knowledge of Antarctic sea-ice changes throughout the last glacial–interglacial cycle is extremely limited. As part of the Cycles of Sea Ice Dynamics in the Earth system (C-SIDE) Working Group, we review marine- and ice-core-based sea-ice proxies to provide insights into their applicability and limitations. By compiling published records, we provide information on Antarctic sea-ice dynamics over the past 130 000 years.