Recent  

The analysis of the dynamics of western central Mediterranean droughts for 850–2099 CE in the Community Earth System Model indicates that past Mediterranean droughts were driven by the internal variability. This internal variability is more important during the initial years of droughts. During the transition years, the longevity of droughts is defined by the land–atmosphere feedbacks. In the future, this land–atmosphere feedbacks are intensified, causing a constant dryness over the region.

The Last Interglacial period (LIG) is characterised by strong orbital forcing compared to the pre-industrial period (PI). This study compares the mean climate state of the LIG to the PI as simulated by the ACCESS-ESM1.5, with a focus on the southern hemispheric monsoons, which are shown to be consistently weakened. This is associated with cooler terrestrial conditions in austral summer due to decreased insolation, and greater pressure and subsidence over land from Hadley cell strengthening.

Using the temperature-dependent solubility of noble gases in ocean water, we reconstruct global mean ocean temperature (MOT) over the last 700 kyr using noble gas ratios in air enclosed in polar ice cores. Our record shows that glacial MOT was about 3 °C cooler compared to the Holocene. Interglacials before 450 kyr ago were characterized by about 1.5 °C lower MOT than the Holocene. In addition, some interglacials show transient maxima in ocean temperature related to changes in ocean circulation.

Uncertainties in climate proxy records are temporally autocorrelated. By deriving expressions for the power spectra of errors in proxy records, we can estimate appropriate uncertainties for any timescale, for example, for temporally smoothed records or for time slices. Here we outline and demonstrate this approach for climate proxies recovered from marine sediment cores.

Maps and fields of near-sea-surface temperature differences between the past and present can be used to visualize and quantify climate changes and perform simulations with climate models. We used a statistical method to map sparse and scattered data for the Last Glacial Maximum time period (23 000 to 19 000 years before present) to a regular grid. The estimated global and tropical cooling would imply an equilibrium climate sensitivity in the lower to middle part of the currently accepted range.

This paper focuses on the recovery of instrumental weather records available for Singapore and Malaysia (Straits Settlements) from the late 1780s to 1917. Taking a historical approach, the paper explores the types of records available, the circumstances of their production and their value to the scientific community.

This modeling study of the Last Glacial Maximum (LGM, ~ 21 000 years ago) ocean explores the biological and physical changes in the ocean needed to satisfy marine proxy records, with a focus on the carbon isotope ¹³C. We estimate that the LGM ocean may have been up to twice as efficient at sequestering carbon and nutrients at depth as compared to preindustrial times. Our work shows that both circulation and biogeochemical changes must have occurred between the LGM and preindustrial times.

This paper utilises a novel palaeoclimate archive from caves, cryogenic cave carbonates, which allow for precisely constraining permafrost thawing events in the past. Our study provides new insights into the climate of the Younger Dryas (12 800 to 11 700 years BP) in mid-Europe from the perspective of a high-elevation cave sensitive to permafrost development. We quantify seasonal temperature and precipitation changes by using a heat conduction model.

The similarity between indirect observations of past climates and information from climate simulations can increase our understanding of past climates. The further we look back, the more uncertain our indirect observations become. Here, we discuss the technical background for such a similarity-based approach to reconstruct past climates for up to the last 15 000 years. We highlight the potential and the problems.

At approximately 14 Ma, the East Antarctic Ice Sheet expanded to almost its current extent, but the role of CO₂ in this major climate transition is not entirely known. We show that atmospheric CO₂ might have varied on 400 kyr cycles linked to the eccentricity of the Earth’s orbit. The resulting change in weathering and ocean carbon cycle affected atmospheric CO₂ in a way that CO₂ rose after Antarctica glaciated, helping to stabilize the climate system on its way to the “ice-house” world.

A very high quality 160-year-long annually laminated (varved) sediment sequence of fluvial origin was recently discovered in an especially deep lake in Labrador. Each varve represents 1 hydrological year. A significant relation between varves' physical parameters (i.e., thickness and grain size extracted from each annual lamination) and river discharge instrumental observations provided the opportunity to develop regional discharge reconstructions beyond the instrumental period.

This study analyzes the impacts of changing vegetation and atmospheric dust concentrations over an area that is currently desert (the Sahara) to investigate their impacts on tropical cyclone activity during a warm climate state, the mid-Holocene. Our results suggest a significant change in Atlantic TC frequency, intensity and seasonality when considering the effects of a warmer climate in a greener world. They also highlight the importance of considering these factors in future climate studies.

The 13 kyr BP Laacher See eruption impacted local environments, human communities and climate. We have simulated the evolution of its fine ash and sulfur cloud such that it reflects the empirically known ash distribution. In our models, the heating of the ash causes a mesocyclone which changes the dispersion of the cloud itself, resulting in enhanced transport to low latitudes. This may partially explain why no Laacher See ash has yet been found in Greenlandic ice cores.

The stability of the Atlantic Meridional Overturning Circulation (AMOC) critically depends on its mean state. We simulate the response of the AMOC to North Atlantic freshwater perturbations under different glacial boundary conditions. We find that a closed Bering Strait greatly increases the AMOC's sensitivity to freshwater hosing. Further, the shift from mono- to bistability strongly depends on the chosen boundary conditions, with weaker circulation states exhibiting more abrupt transitions.

Productive eastern boundary upwelling systems (EBUs) are characterized by abundant siliceous algae and diatoms, and they play a key role in carbon fixation. Understanding past shifts in diatom production is critical for predicting the impact of future climate change. We combine existing sediment archives from the Benguela EBU with new diatom isotope analyses and modelling to reconstruct late Quaternary silica cycling, which we suggest depends on both upwelling intensity and surface utilization.

Cosmogenic ¹⁰Be exposure dates from outlying islets along 300 km of the SW Greenland coast indicate that, although affected by inherited ¹⁰Be, the ice margin here was retreating during the Younger Dryas. These results seem to be corroborated by recent studies elsewhere in Greenland. The apparent mismatch between temperatures and ice margin behaviour may be explained by the advection of warm water to the ice margin on the shelf and by increased seasonality, both caused by a weakened AMOC.

Volcanic eruptions are a key source of climatic variability, and greater understanding of their past influence will increase the accuracy of future projections. We use volcanic ash from a 1477 CE Icelandic eruption in a Greenlandic ice core as a temporal fix point to constrain the timing of two eruptions in the 1450s CE and their climatic impact. Despite being the most explosive Icelandic eruption in the last 1200 years, the 1477 CE event had a limited impact on Northern Hemisphere climate.

The palaeoclimate community must both analyse large amounts of model data and compare very different climates. Here, we present a seemingly very abstract analysis approach that may be fruitfully applied to palaeoclimate numerical simulations. This approach characterises the dynamics of a given climate through a small number of metrics and is thus suited to face the above challenges.

The last interglacial was a warm period that may provide insights into future climates. Here, we compile and analyse stable carbon isotope data from the ocean during the last interglacial and compare it to the Holocene. The data show that Atlantic Ocean circulation was similar during the last interglacial and the Holocene. We also establish a difference in the mean oceanic carbon isotopic ratio between these periods, which was most likely caused by burial and weathering carbon fluxes.

The Atlantic Meridional Overturning Circulation (AMOC) is an important topic in the Pliocene Model Intercomparison Project. Previous studies have suggested a much stronger AMOC during the Pliocene than today. However, our current multi-model intercomparison shows large model spreads and model–data discrepancies, which can not support the previous hypothesis. Our study shows good consistency with future projections of the AMOC.

We present the first Fe record from the NEEM ice core, which provides insight into past atmospheric Fe deposition in the Arctic. Considering the biological relevance of Fe, we questioned if the increased eolian Fe supply during glacial periods could explain the marine productivity variability in the Fe-limited subarctic Pacific Ocean. We found no overwhelming evidence that eolian Fe fertilization triggered any phytoplankton blooms, likely because other factors play a more relevant role.