Extremes of the past: what interglacial periods reveal about weather of the future

Extreme weather represents one of the most significant consequences of a warming climate. Improving constraints on how such events may manifest in the future is therefore a key priority, particularly for hazards that lead to severe societal, ecological, and financial impacts, such as heatwaves, extreme rainfall, droughts and their compounding effects.Past interglacial periods provide physically realised instances of warm-climate states that can be used to contextualise ongoing anthropogenic warming and to inform future changes. Each interglacial is characterised by a distinct combination of orbital forcing and greenhouse gas concentrations, ice-sheet configuration, and background climate. Comparing these periods allows the partial isolation of the roles played by different climate drivers and large-scale circulation patterns in shaping the frequency, intensity, variability and spatial distribution of extreme events.Here, we compare extreme weather characteristics across four interglacial periods: the mid-Holocene (6 ka), the Last Interglacial (127 ka), Marine Isotope Stage 11 (408 ka), and Marine Isotope Stage 31 (1072 ka), alongside a pre-industrial control. The analysis is based on preliminary equilibrium time-slice simulations conducted using the HadGEM3-GC5.0 coupled climate model, which also enables an initial assessment of model performance across a range of interglacial climates. We demonstrate how distinct warm-climate conditions have affected polar and global extreme events in the past and discuss the mechanisms underpinning these changes and their relevance for future climates.