Underestimated Ural blocking events lead to weakened spring Arctic warming in CMIP6 simulations

Historical Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations underestimate spring Arctic warming due to insufficient representation of Ural blocking events. Observations reveal that strong winter warming over the Barents–Kara Sea (BKS) reduces the meridional potential vorticity gradient, thereby enhancing atmospheric blocking events and driving Arctic surface warming in spring. Many CMIP6 members, which exhibit lower sensitivity to climate forcing, involve the use of initial fields with warmer climate conditions (e.g. reduced sea ice cover). Consequently, these models simulate less sea ice melting and minimal winter BKS warming, leading to weaker Ural blocking events and underestimation of spring Arctic surface warming. While recent global surface temperature trends among CMIP6 models are relatively consistent, their future projections diverge due to their varying climate sensitivities, potentially underestimating global warming across different scenarios.