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.