Human-driven sea-level rise has quadrupled the frequency of coastal sea-level extremes since 1900

Coastal flooding events are escalating worldwide, yet the role of human-driven sea-level rise remains poorly constrained. Here we provide a global detection and attribution of changes in extreme sea-level frequency since 1900, combining tide-gauge records with historical and single-forcing experiments from the Coupled Model Intercomparison Project Phase 5. We show that relative sea-level rise, driven primarily by anthropogenic radiative forcing since the 1960s, has already transformed the likelihood of historically rare extremes. Globally, the median frequency of an historical 1-in-100-year extreme sea-level event has increased ~12-fold, with human-driven radiative forcing alone quadrupling the likelihood of such events. Natural variability still modulates regional patterns but has become secondary along most coastlines. These findings provide direct, observation-based evidence that climate change has already reshaped coastal flood hazard, underscoring the urgency of integrating attribution science into coastal adaptation, risk management and policy frameworks.