Arctic Warming Surpasses Estimates Constrained by Early 21st Century Albedo

Arctic warming has exceeded the global average and is projected to intensify, yet models may still underestimate its magnitude. Here, we apply a novel decomposition method to quantify the contributions of sea ice albedo, concentration, and extent to Arctic surface albedo trends in observations and CMIP6 models. While sea ice extent dominates the long-term decline, sea ice albedo strongly influenced observed variability in the early 21st century—a signal largely absent in models. This missing feedback results in up to 1.5 K (~20%) additional summer warming under SSP585. Crucially, models with present-day albedo trends more consistent with observations—particularly those driven by sea ice extent loss—project stronger future albedo feedback and greater Arctic warming. This emergent relationship provides a physically grounded constraint on long-term projections. Our findings underscore the importance of realistic sea ice process representation and demonstrate that recent changes in ice edge can inform future climate response.