Stalagmites formed in caves provide valuable information about past changes in climate and vegetation conditions. In this contribution, we present a new method to better estimate past changes in soil and vegetation productivity using carbon isotopes and trace elements measured in stalagmites. Applying this method to other stalagmites should provide a better indication of past vegetation feedbacks to climate change.

A Green Sahara with enhanced rainfall and larger vegetation cover existed in northern Africa about 6000 years ago. Biosphere–atmosphere interactions are found to be critical to explaining this wet period. Based on modeled vegetation reconstruction data, we simulated dust emissions and aerosol formation, which are key factors in biosphere–atmosphere interactions. Our results also provide a benchmark of aerosol climatology for future paleo-climate simulation experiments.

We study the climate signal in long harvest series from across Europe between the 16th and 18th centuries. The climate–harvest yield relationship is found to be relatively weak but regionally consistent and similar in strength and sign to modern climate–harvest yield relationships. The strongest climate–harvest yield patterns are a significant summer soil moisture signal in Sweden, a winter temperature and precipitation signal in Switzerland, and spring temperature signals in Spain.

We evaluate how faithfully the boron isotope composition of foraminifera records atmospheric CO₂ by comparing it to the high-fidelity CO₂ record from the Antarctic ice cores. We evaluate potential factors and find that partial dissolution of foraminifera shells, assumptions of seawater chemistry, and the biology of foraminifera all have a negligible effect on reconstructed CO₂. This gives confidence in the use of boron isotopes beyond the interval when ice core CO₂ is available.

In this study, we investigate circulation patterns associated with Mediterranean droughts during the last millennium using global climate simulations. Different circulation patterns driven by internal interactions in the climate system contribute to the occurrence of droughts in the Mediterranean. The detected patterns are different between the models, and this difference can be a potential source of uncertainty in model–proxy comparison and future projections of Mediterranean droughts.

Atmospheric levels of molecular hydrogen (H₂) can impact climate and air quality. Constraining past changes to atmospheric H₂ is useful for understanding how H₂ cycles through the Earth system and predicting the impacts of increasing anthropogenic emissions under the hydrogen economy. Here, we use the aging air found in the polar snowpack to reconstruct H₂ levels over the past 100 years. We find that H₂ levels increased by 30 % over Greenland and 60 % over Antarctica during the 20th century.

We investigated the different boundary conditions to allow ice sheet growth and ice sheet decline of the Antarctic ice sheet when it appeared ∼38–34 Myr ago. The thresholds for ice sheet growth and decline differ because of the different climatological conditions above an ice sheet (higher elevation and higher albedo) compared to a bare topography. We found that the ice–albedo feedback and the isostasy feedback respectively ease and delay the transition from a deglacial to glacial state.

Oceanic Anoxic Event 2 (OAE 2), about 93.5 million years ago, is characterized by widespread deoxygenated ocean and massive burial of organic-rich sediments. Our results show that the marine deoxygenation at the equatorial Atlantic that predates the OAE 2 interval was driven by global warming and associated with the nutrient status of the site, with factors like temperature-modulated upwelling and hydrology-induced weathering contributing to enhanced nutrient delivery over various timescales.