HAWAII — The National Oceanic and Atmospheric Administration warned on a Tuesday in 2026 that an anticipated El Niño could trigger a fifth global coral bleaching event. NOAA’s updated coral bleaching outlook places Hawaii and much of the northern Pacific Ocean at high risk of bleaching this summer.
This potential event would mark the fifth global coral bleaching incident in recorded history. Global coral bleaching events have coincided with every strong El Niño since 1998. Scientists are fairly certain El Niño will arrive before fall 2026, though its exact timing and strength remain under assessment. If it emerges as anticipated, widespread coral bleaching could occur between June and September.
Reefs surrounding Florida and the Caribbean may also face high bleaching risk later this summer, according to NOAA’s outlook. Higher ocean temperatures cause coral to lose their pigments and turn white, a process known as coral bleaching. Sea surface temperatures are currently higher than during the first global coral bleaching event in 1998.
The fourth global coral bleaching event, which NOAA confirmed on April 15, 2024, impacted 84% of the world’s coral reef area and ended in mid-2025. From early 2023 to mid-2025, bleaching-level heat stress affected reefs across the Pacific, Atlantic, and Indian Oceans, with mass bleaching documented in at least 83 countries and territories. The severe bleaching in Western Australia in early 2025 likely marked the end of that event.
Derek Manzello, Coordinator of NOAA’s Coral Reef Watch, said in a statement: 'We are now in the era where reefs will bleach on a near-annual basis, which means defining when global events begin and end is becoming increasingly difficult.' He added: 'The plan moving forward is to rely on field bleaching observations to determine if and when global events are happening.' Manzello also stated: 'Thermal stress is now pervasive on our nation’s coral reefs.' He emphasized that 'frequent, regular monitoring is more vital now than ever before, as it is the only way to understand the biological and physical factors associated with bleaching resilience from the organism to ecosystem level.'
Jennifer Koss, Director of NOAA’s Coral Reef Conservation Program, said: 'NOAA and its partners are studying multiple aspects of heat tolerance in corals.' She added: 'This will help us better understand resilience in corals and improve coral restoration strategies and techniques across the nation.' Coral reefs provide habitats for approximately one-fourth of all marine species.