articleCoral ReefsJan 29, 2026HYBRID OA

The 4th global coral bleaching event: ushering in an era of near-annual bleaching

NOAA National Environmental Satellite Data and Information Service · Global Science & Technology (United States) · +6 more institutions

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Abstract

Abstract Increasingly frequent marine heatwaves have escalated the prevalence and extent of mass coral bleaching events. Global-scale coral bleaching events (GCBEs) can unfold when marine heatwaves impact reefs across all tropical ocean basins within a common period. Here, we define an objective, quantifiable index to compare periods of satellite-derived coral heat stress accumulation globally from 1985 to 2025 and examine their relationship to confirmed GCBEs. We uncover an uninterrupted and ongoing period of global coral heat stress from 2018 to 2025, affecting an unprecedented 87% of reef areas globally. The average intensity has also been record-setting, with the median global heat stress accumulation on…

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