Abstract

Recent results confirm that the last time the Arctic was sea ice-free occurred 127,000 years ago. Until recently, climate models have struggled to simulate a complete loss of Arctic summer sea ice during the Last Interglacial (LIG). Given the significantly higher summer insolation at that time, there is strong motivation to closely examine this period and conduct climate model simulations to assess whether models can accurately capture the extreme warming and sea ice loss that previous simulations failed to replicate. In this talk, as well as the evidence for a sea ice free Arctic, I will present the new Intergovernmental Panel on Climate Change (IPCC) Seventh Assessment Report (AR7) Coupled Model Intercomparison Project (CMIP7)–Paleoclimate Model Intercomparison Project (PMIP) FastTrack abrupt-127k protocol, which aims to address these challenges. By improving our understanding of model performance in this out-of-sample test, the FastTrack results should provide crucial insights into: key model physics; why the Arctic was sea ice free; and future Arctic sea ice model-derived projections.