Recent  

In this work, we use the same experimental protocol to simulate the last two glacial terminations with a coupled ice sheet–climate model. Major differences among the two terminations are that the ice sheets retreat earlier and the Atlantic oceanic circulation is more prone to collapse during the penultimate termination. However, for both terminations the pattern of ice retreat is similar, and this retreat is primarily explained by orbital forcing changes and greenhouse gas concentration changes.

To trigger glacial inception, the summer maximum insolation at high latitudes in the Northern Hemisphere must be lower than a critical value. This value is not constant but depends on the atmospheric CO₂ concentration. Paleoclimatic data do not give enough information to derive the relationship between the critical threshold and CO₂. However, knowledge of such a relation is important for predicting future glaciations and the impact anthropogenic CO₂ emissions might have on them.

Export productivity is part of the global carbon cycle, influencing the climate system via biological pump. About 34 million years ago, the Earth's climate experienced a climate transition from a greenhouse state to an icehouse state with the onset of ice sheets in Antarctica. Our study shows important productivity events in the Southern Ocean preceding this climatic shift. Our findings strongly indicate that the biological pump potentially played an important role in that past climate change.

Polar amplification (PA) is a key uncertainty in climate projections. The factors that dominantly control PA are difficult to separate. Here we provide an estimate for the non-ice-related PA by reconstructing tropical ocean temperature variability from the ice-free early Eocene, which we compare to deep-ocean-derived high-latitude temperature variability across short-lived warming periods. We find a PA factor of 1.7–2.3 on 20 kyr timescales, which is somewhat larger than model estimates.

At present, under low eccentricity, the tropical ocean experiences a limited seasonality. Based on eight climate simulations of sea surface temperature and primary production, we show that, during high-eccentricity times, significant seasons existed in the tropics due to annual changes in the Earth–Sun distance. Those tropical seasons are slowly shifting in the calendar year to be distinct from classical seasons. Their past dynamics should have influenced phenomena like ENSO and monsoons.

There is a lack of reconstructions from Antarctic ice cores of the temperature during the summer, a critical season in terms of solar energy received, preventing a good understanding of the link between Antarctic past climate and astronomically induced insolation changes. Here, the variations in total air content in an Antarctic ice core are found to be correlated to local summer temperatures simulated with a climate model. This tracer can be used to reconstruct past local summer temperatures.

Glaciers in the European Alps have been retreating since the 1850s. Monitoring glacier mass balance is vital for understanding global changes, but only a few glaciers have long-term data. This study aims to reconstruct the mass balance of the Silvretta Glacier in the Swiss Alps using stable isotopes and tree ring proxies. Results indicate increased glacier mass until the 19th century, followed by a sharp decline after the Little Ice Age with accelerated losses due to anthropogenic warming.

The Atlantic Meridional Overturning Circulation (AMOC) is an ocean current that transports heat into the North Atlantic. Over the ice age cycles, AMOC strength and its spatial pattern varied. We tested the role of heat forcing for these AMOC changes by simulating the temperature changes of the last eight glacial cycles. In our model, AMOC shifts between four distinct circulation modes caused by heat and salt redistributions that reproduce reconstructed long-term North Atlantic SST changes.

In 2018, a new 120 m ice core was drilled in a region located under the Antarctic ozone hole. We present the first results including a 1300-year record of snow accumulation and aerosol chemistry. We investigate the aerosol and moisture source regions and atmospheric processes related to the ice core record and discuss what this means for developing a record of past ultraviolet radiation and ozone depletion using the stable isotopic composition of nitrate measured in the same ice core.

We analyse simulations with idealised aerosol scenarios to examine the importance of aerosol forcing on mPWP precipitation and how aerosol uncertainty could explain the data–model mismatch. We find further warming, a narrower and stronger ITCZ, and monsoon domain rainfall change after removal of industrial emissions. Aerosols have more impacts on tropical precipitation than the mPWP boundary conditions. This highlights the importance of prescribed aerosol scenarios in simulating mPWP climate.

The Pliocene (~ 3 million years ago) is of interest because its warm climate is similar to projections of the future. We explore the role of atmospheric carbon dioxide in forcing sea surface temperature during the Pliocene by combining climate model outputs with palaeoclimate proxy data. We investigate whether this role changes seasonally and also use our data to suggest a new estimate of Pliocene climate sensitivity. More data are needed to further explore the results presented.

Radiocarbon proxies suggest that the deep waters are poorly ventilated during the Last Glacial Maximum (LGM). Here we use two transient simulations with tracers of radiocarbon and ideal age to show that the deep-ocean ventilation age is not much older at the LGM compared to the present day because of the strong glacial Antarctic Bottom Water transport. In contrast, the ventilation age is older during deglaciation mainly due to weakening of Antarctic Bottom Water transport.

A Little Ice Age (LIA) hurricane was characterized using key storm intensity metrics from historical naval records. Its unusual intensity was driven by a higher temperature gradient between continental and coastal atmospheric circulation that drove intense midlatitude extratropical transition. Quantitative attributes embedded in historical records allow multidisciplinary research to extend our understanding of climate processes through the historical period.  

The Southern Annular Mode (SAM) influences climate in the Southern Hemisphere. We investigate the effects of calculation method and data used to calculate the SAM index and how it influences the relationship between the SAM and climate. We propose a method to calculate a natural SAM index that facilitates consistency between studies, including when using different data resolutions, avoiding distortion of SAM impacts and allowing for more reliable results of past and future SAM trends.

Analysing a sediment record from Stóra Viðarvatn (NE Iceland), we reveal how natural factors and human activities influenced environmental changes (erosion, wildfires) over the last 11 000 years. We found increased fire activity around 3000 and 1500 years ago, predating human settlement, likely driven by natural factors like precipitation shifts. Declining summer temperatures increased erosion vulnerability, exacerbated by farming and animal husbandry, which in turn may have reduced wildfires.

Elevated atmospheric CO₂ concentrations and a smaller Antarctic Ice Sheet during the mid-Pliocene (~ 3 million years ago) cause the Southern Ocean surface to become fresher and warmer, which affects the global ocean circulation. The CO₂ concentration and the smaller Antarctic Ice Sheet both have a similar and approximately equal impact on the Southern Ocean. The conditions of the Southern Ocean in the mid-Pliocene could therefore be analogous to those in a future climate with smaller ice sheets.

The Great Plains host the single most important climatic boundary in North America, separating the humid east from the semi-arid west. How this boundary will move as the world warms holds implications for the societies and ecosystems of the Plains. We study how this boundary changed in the past during a period of globally warmer temperatures. We find that this climatic boundary appears to be in the same location as today, suggesting that the Great Plains climate is resilient to global changes.

The newly developed series of wheat, rye, barley, and oats prices from Sušice (southwestern Bohemia) for the period 1725–1824 CE is used to demonstrate effects of weather, climate, socio-economic, and societal factors on their fluctuations, with particular attention paid to years with extremely high prices. Cold spring temperatures and wet conditions from winter to summer were reflected in very high grain prices.