Peatlands hold valuable insights about past climate, but the link between tree growth and water conditions remains unclear. We analyzed tree-ring stable isotopes from Scots pines in Swedish peatlands to study their response to water levels and climate. Unlike tree-ring widths, stable isotopes showed strong, consistent signals of water table levels and summer climate. This improves our ability to reconstruct past climate changes from peatland trees.

For the first time, we provide a regional climate model with past climate forcings. The model's sensitivity to each forcing is tested in a case study around the large Samalas volcanic eruption in 1257. The orbital forcing shows the largest effect with an amplification of the seasons in the past compared with the standard model. The volcanic forcing has a strong short-term cooling effect after the volcanic eruption. This model is later used for a transient simulation of the last 2500 years.

We used climate models to study how stable water isotopes in ice cores changed in the Arctic and Antarctica during the warm Last Interglacial (LIG) period. Whilst standard simulations underestimate polar warming, when the effects of ice sheet meltwater from the preceding deglaciation are included, there is a much better match with observations. Findings suggest that previous estimates of LIG Arctic warming were too high. Understanding these past polar changes can help improve future predictions.

Large volcanic eruptions can trigger global cooling, affecting human societies. Using ice-core records and simple climate model to simulate volcanic effect over the last 8500 years, we show that volcanic eruptions cool the climate by 0.12 °C on average. By comparing model results with temperature recorded by tree rings over the last 1000 years, we demonstrate that our models can predict the large-scale cooling caused by volcanic eruptions and can be used in cases of large eruptions in the future.

In our study, we investigate changes in environment and climate that occured during post-Holsteinian period in Krępa palaeolake (eastern Poland). To achieve this goal we reconstructed summer temperature at the time using Chironomidae larvae head capsules and pollen data. This is first research from Central Europe with both chironomids and pollen used to trace climate change through post-Holsteinian period. We hope to encourage scientific community to carry out further research in the region.

Data assimilation (DA) has been used to reconstruct paleoclimate fields. DA integrates model simulations and climate proxies based on their error sizes. Consequently, error information is vital for DA to function optimally. This study estimated observation errors using "innovation statistics" and demonstrated that DA with estimated errors outperformed previous studies.

Continental-scale temperature maps have been generated based on rodent associations and spatial generalized linear mixed model for six different periods (Last Glacial Maximum, Heinrich Stadial, Bølling, Allerød, Younger Dryas and present-day conditions). Their reliability was assessed by comparing them with general circulation models, showing similar estimates, but slightly colder values in western Europe and warmer ones in eastern Europe for past periods.

The pore density (number of pores per unit area) of unicellular eukaryotes is used to reconstruct past bottom-water nitrate at the Sea of Okhotsk, the Gulf of California, the Mexican Margin and the Gulf of Guayaquil. The reconstructed bottom-water nitrate at the Sea of Okhotsk, the Gulf of California and the Gulf of Guayaquil are influenced by the intermediate water masses, while the nitrate at the Mexican Margin is related to the deglacial NO₃⁻ variability in the Pacific Deep Water.

The deep ocean is an important part of the global climate system. Accurate estimates of temperature changes at depth are crucial to understand the role of the intermediate to deep ocean in climate change. We have used samples from the Indian Ocean to establish Mg/Ca-based temperature calibrations based on benthic foraminifera. Our data suggest that generating optimal Mg/Ca ratios in benthic foraminifera may require species- and region-specific cleaning procedures.