Arctic winter sea ice loss may exceed forecasts by 1 million km²

Researchers at the University of Cambridge and Mexico's CIMAT used sediment records from a warmer Arctic 6,000 years ago to refine climate models, finding winter sea ice may shrink by about 1 million km² more than previously projected. Bayesian weighting cut uncertainty in some projections by up to 85%.

• Winter ice loss forecast is underestimated by about 1 million km²
• Study used 27 climate models and the IP25 biomarker from sediment cores
• Uncertainty range narrowed by as much as 85% in some projections
• Winter sea ice hit record-low maximums in March 2025 and 2026