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In this study a set of simulations are performed with the regional climate model COSMO-CLM for Europe, for the mid-Holocene and pre-industrial periods. The main aim is to better understand the drivers of differences between models and pollen-based summer temperatures. Results show that a fundamental role is played by spring soil moisture availability. Additionally, results suggest that model bias is not stationary, and an optimal configuration could not be the best under different forcing.

Building upon Milancovic's theory of orbital forcing, this paper reviews the interplay between intrinsic variability and external forcing in the emergence of glacial interglacial cycles. It provides the reader with historical background information and with basic theoretical concepts used in recent paleoclimate research. Moreover, it presents new results which confirm the reduced stability of glacial-cycle dynamics after the mid-Pleistocene transition.

Climate models are used to predict future climate changes and as such, it is important to assess their performance in simulating past climate changes. We analyze seasonal sea-ice cover over the Southern Ocean simulated from numerical PMIP3, PMIP4 and LOVECLIM simulations during the Last Glacial Maximum (LGM). Comparing these simulations to proxy data, we provide improved estimates of LGM seasonal sea-ice cover. Our estimate of summer sea-ice extent is 20 %–30 % larger than previous estimates.

This paper introduces a new R package to perform quantitative climate reconstructions from palaeoecological datasets. The package includes calibration data for several commonly used terrestrial (e.g. pollen) and marine (e.g. foraminifers) climate proxies to enable its use in various environments globally. In addition, the built-in graphical diagnostic tools simplify the evaluation and interpretations of the results. No coding skills are required to use crestr.

We unearth and analyse 2 decades of highly valuable measurements made on Mauritius at the Royal Alfred Observatory, where several distinct thermometer combinations were in use and compared, at the turn of the 20th century. This series provides unique insights into biases in early instrumental temperature records. Differences are substantial and for some instruments exhibit strong seasonality. This reinforces the critical importance of understanding early instrumental series biases.

This study examines whether the 1600 Huaynaputina volcano eruption triggered persistent cooling in the North Atlantic. It compares previous paleoclimate simulations with new climate reconstructions from natural proxies and historical documents and finds that the reconstructions are consistent with, but do not support, an eruption trigger for persistent cooling. The study also analyzes societal impacts of climatic change in ca. 1600 and the use of historical observations in model–data comparison.

To better understand the climate conditions which lead to extensive melting of the Greenland ice sheet, we used climate models to reconstruct the climate conditions of the warmest period of the last 800 000 years, which was centered around 410 000 years ago. Surprisingly, we found that atmospheric circulation changes may have acted to reduce the melt of the ice sheet rather than enhance it, despite the extensive warmth of the time.

After the Marinoan snowball Earth, the climate warmed rapidly due to enhanced greenhouse conditions, and the freshwater inflow of melting glaciers caused a strong stratification of the ocean. Our climate simulations reveal a potentially only moderate global temperature increase and a break-up of the stratification within just a few thousand years. The findings give insights into the environmental conditions relevant for the geological and biological evolution during that time.

The timing of the initiation and evolution of the South Asian monsoon in the geological past is a subject of debate. Here, we present a new age model spanning the late Miocene (9 to 5 million years ago) and high-resolution records of past open-ocean biological productivity from the equatorial Indian Ocean that we interpret to reflect monsoon wind strength. Our data show no long-term intensification; however, strong orbital periodicities suggest insolation forcing of monsoon wind strength.

New stable isotope records from pedogenic carbonates through the ETM2, H2, and possibly I1 hyperthermals from the Bighorn Basin highlight significant spatial variability in the preservation and magnitude of these global climate events in paleosol records. These data also provide important climate context for the extensive early Eocene mammal fossil record from the southern Bighorn Basin and support previous hypotheses that pulses in mammal turnover corresponded to the ETM2 and H2 hyperthermals.

The Pliocene was a period during which atmospheric CO₂ was similar to today (i.e. ~ 400 ppm). We present the results of model simulations carried out within the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) using the CESM 1.0.5. We find a climate that is much warmer than today, with augmented polar warming, increased precipitation, and strongly reduced sea ice cover. In addition, several leading modes of variability in temperature show an altered behaviour.

Carbon monoxide (CO) is a regulated pollutant and one of the key components determining the oxidizing capacity of the atmosphere. In this study, we analyzed five ice cores from Greenland at high resolution for CO concentrations by coupling laser spectrometry with continuous melting. By combining these new datasets, we produced an upper-bound estimate of past atmospheric CO abundance since preindustrial times for the Northern Hemisphere high latitudes, covering the period from 1700 to 1957 CE.

We report the discovery, examination and interpretation of a unique type of data source, i.e., the 19th century monthly water level observation of a reservoir named Lake Machang on the Grand Canal in China. The water level changes of the reservoir on monthly and annual scales were compared with relevant precipitation and hydrology chronologies. The relationship of the evolution of the reservoir with the flooding of the Yellow River and reclamation is discussed.

The Last Interglacial (129–116 ka) is characterised by an increased summer insolation over the Arctic region, which leads to a strong temperature rise. The aim of this study is to identify and quantify the main processes and feedback causing this Arctic warming. Using the IPSL-CM6A-LR model, we investigate changes in the energy budget relative to the pre-industrial period. We highlight the crucial role of Arctic sea ice cover, ocean and clouds on the Last Interglacial Arctic warming.

Earth experiences regular ice ages resulting in shifts between cooler and warmer climates. Around 1 million years ago, the ice age cycles grew longer and stronger. We used bacterial and plant lipids preserved in an Arctic lake to reconstruct temperature and vegetation during this climate transition. We find that Arctic land temperatures did not cool much compared to ocean records from this period, and that vegetation shifts correspond with a long-term drying previously reported in the region.

This paper synthesizes 66 records of glacier variations over the Holocene from lake archives across seven Arctic regions. We find that summers only moderately warmer than today drove major environmental change across the Arctic in the early Holocene, including the widespread loss of glaciers. In comparison, future projections of Arctic temperature change far exceed estimated early Holocene values in most locations, portending the eventual loss of most of the Arctic's small glaciers.

Over the last 2.6 Myr, the Quaternary period has been marked by the alternation of extended and reduced Northern Hemisphere ice sheets, known as glacial-interglacial cycles. With a simple model, we are able to reproduce the main features of the ice volume evolution, like the switch of periodicity, from 41 kyr cycles to 100 kyr cycles, observed in the data after 1 Ma. The quality of the model-data agreement depending on the input insolation and period considered is discussed.

Late Eocene to earliest Oligocene (37.97–33.06 Ma) climate and vegetation dynamics around the Tasmanian Gateway region reveal that changes in ocean circulation due to accelerated deepening of the Tasmanian Gateway may not have been solely responsible for the changes in terrestrial climate and vegetation; a series of regional and global events, including a change in stratification of water masses and changes in pCO₂, may have played significant roles.

We investigate the effects of a warmer climate from the Earth's paleoclimate (last interglacial) on the marine carbon cycle of the Southern Ocean using a carbon-cycle-enabled state-of-the-art climate model. We find a 150 % increase in CO₂ outgassing during this period, which results from competition between higher sea surface temperatures and weaker oceanic circulation. From this we unequivocally infer that the carbon uptake by the Southern Ocean will reduce under a future warming scenario.

We employ acidity records from Greenland and Antarctic ice cores to estimate the emission strength, frequency and climatic forcing for large volcanic eruptions from the last half of the last glacial period. A total of 25 volcanic eruptions are found to be larger than any eruption in the last 2500 years, and we identify more eruptions than obtained from geological evidence. Towards the end of the glacial period, there is a notable increase in volcanic activity observed for Greenland.

We provide new winter sea ice and summer sea surface temperature estimates for marine core TAN1302-96 (59° S, 157° E) in the Southern Ocean. We find that sea ice was not consolidated over the core site until ~65 ka and therefore believe that sea ice may not have been a major contributor to early glacial CO₂ drawdown. Sea ice does appear to have coincided with Antarctic Intermediate Water production and subduction, suggesting it may have influenced intermediate ocean circulation changes.

We test a new method to reconstruct past atmospheric CO₂ levels based on the geochemistry of pelagic algal biominerals (coccoliths), which recent culture and numerical experiments have related to ambient CO₂ concentrations. By comparing the isotopic composition of fossil coccoliths to the inferred surface ocean CO₂ level at the time they calcified, we outline a transfer function and argue that coccolith vital effects can be used to reconstruct geological pCO₂ beyond the ice core record.

This article finds that grain farming in historical Scania (ca. 1700–1900) was adapted to wet and cold summers, while being resilient to frost and climate variability in the spring and autumn. These relationships started to change in the late 19th century with the introduction of new grain varieties, particularly autumn grain varieties. Nonetheless, historical farmers faced a threat in common with contemporary farmers, namely summer droughts, like the summer drought of 2018.

In this study, we applied geochemical tools to well-preserved ∼180-million-year-old marine mollusc shells from polar and mid-latitude seas. These results indicate that polar shells grew at temperatures of 8–18°C, while mid-latitude shells grew at temperatures of 24–28°C. These results, together with previously published data, raise concerns about the ability of climate models to predict accurate polar temperatures under reasonably high atmospheric CO₂ levels.

Sea ice is important for our climate system and for the unique ecosystems it supports. We present a novel way to understand past Antarctic sea-ice ecosystems: using the regurgitated stomach contents of snow petrels, which nest above the ice sheet but feed in the sea ice. During a time when sea ice was more extensive than today (24 000–30 000 years ago), we show that snow petrel diet had varying contributions of fish and krill, which we interpret to show changing sea-ice distribution.

We investigated the diversity of algae called diatoms in Lake Baikal, the oldest and deepest lake in the world, because algae sit at the base of aquatic foodwebs and provide energy (in the form of primary production) for other organisms to use. Diatom diversity and primary production have been influenced by both long-term and abrupt climate change over the past 16 000 years. The shape of these responses appears to be time-period specific.

Temperature seasonality is an important climate parameter for biodiversity. Fossil plants describe its middle Eocene to early Oligocene increase in the Northern Hemisphere, but underlying mechanisms have not been studied in detail yet. Using climate simulations, we map global seasonality changes and show that major contemporary forcing – atmospheric CO₂ lowering, Antarctic ice-sheet expansion and particularly related sea level drop – participated in this phenomenon and its spatial distribution.

The East Asian winter monsoon causes orographic snowfall over the windward side of the Japanese islands (facing the Sea of Japan and the northwesterly winter monsoon flow) and negative temperature anomalies around Japan. In this study, we reconstruct the outbreak of the winter monsoon around Japan for the winter from the 1840s to the early 1850s by using daily weather information recorded in old Japanese diaries and early daily instrumental temperature data.