Record El Niño Strengthens: Pacific Heat Puts World's Coral Reefs at 'Terrifying' Risk, UN Expert Warns

Illustration: a stylized view of record Pacific heat building toward an El Niño peak.

What Happened

The World Meteorological Organization's monthly Global Seasonal Climate Update, published October 13, 2026, says sea-surface temperatures in the central and eastern tropical Pacific are forecast to increase to record levels during October-November-December 2026, reflecting a strengthening El Niño event that will drive weather patterns and impact economies, ecosystems and communities across the globe. The WMO says El Niño will continue to intensify ahead of its forecast peak in December, likely bringing above-average temperatures to much of the globe and shifting rainfall patterns — raising the risk of drought and floods in different regions.

"El Niño is firmly established and strengthening rapidly. WMO forecasts indicate a near-100 per cent likelihood that it will persist through February 2027, potentially being one of the strongest since at least 1950," said WMO Secretary-General Celeste Saulo. The near-certainty figure is not one model but a consensus across thirteen national and international centers — from Washington to Tokyo to London to Pune — built on real-time ocean buoy, satellite and radiosonde data coordinated by the WMO.

The numbers are stark. The widely used Niño 3.4 sea-surface temperature index rose from an average of 1.6°C above normal in June 2026 to 2.5°C above normal in August. For October-November-December, the seasonal average is forecast to reach approximately 3.7°C above normal — the highest since observations began, exceeding the previous record of 2.6°C set in November 2015–January 2016.

Other ocean basins are piling on. A positive Indian Ocean Dipole, which strongly influences rainfall around the Indian Ocean, is expected to peak in October before declining, while sea-surface temperatures in the equatorial Atlantic remain above normal. Earth just recorded its hottest August on record, according to monthly reports from the EU's Copernicus Climate Service, the US National Oceanic and Atmospheric Administration and NASA — and global sea-surface temperature reached an all-time observed high in August.

For coral reefs, the news could not be worse. A super El Niño fueling record ocean temperatures poses a "terrifying" threat to the world's fragile coral reefs, the chair of the UN's expert nature panel told AFP, as reported by phys.org on October 15, 2026. Marine scientist David Obura, a Kenyan reef expert and chair of IPBES — the UN's expert scientific panel on biodiversity — said the exceptional El Niño building strength in the tropical Pacific could drive vulnerable coral species even closer toward extinction. "That this coming event is worse than [1997/98], after three intervening global bleaching events ... is a terrifying reality," he said.

Illustration: a stylized coral reef between healthy color and heat-driven bleaching.

Background

Corals are heat sensitive and particularly vulnerable to climate change, which is heating the world's oceans and increasing the frequency and intensity of damaging bleaching events. El Niño, the warming phase of a natural climate cycle, temporarily elevates global temperatures, alters cloud and wind patterns, and raises the risk of damaging weather — and every strong El Niño since 1998 has been associated with a Global Coral Bleaching Event.

There have been four such global bleaching events, and each has impacted more reefs than the previous one, Derek Manzello, coordinator of NOAA's Coral Reef Watch, told Mongabay in reporting republished this month. Manzello noted that an estimated 8 percent of the world's corals died during the first global event in 1998, with a further 14 percent loss from 2009 to 2018; during the third event, about 15 percent of reefs experienced more than 10 percent coral mortality. A global assessment of the fourth event is still underway, but global coral cover declined by 8.9 percent during 2023–2024.

As background ocean temperatures rise due to global warming, the additional heat of El Niño is more likely to push corals beyond their thermal stress thresholds. "The global mean sea surface temperature from 2019–2023 was equal to the maximum recorded in 1998, which was associated with the first Global Coral Bleaching Event," Manzello said. "Sea surface temperatures during current La Niña conditions are warmer than they were during El Niño events three to four decades ago."

The response is already underway in places. In Costa Rica, researchers with the State Distance University (UNED) have moved approximately 2,700 corals into deeper water near Isla Tortuga in the Gulf of Nicoya, relocating coral nursery structures from around five meters to 13 meters below the surface, where cooler deeper water may reduce heat stress, NewsNation Online reported on October 17, 2026. Monitoring of temperatures, salinity and coral health has been intensified as part of the marine restoration project — a protective intervention, not a guarantee, as bleaching does not always mean death and some corals recover if temperatures fall.

Australia's Great Barrier Reef remains in serious ecological danger despite staying off UNESCO's danger list, with five mass coral bleaching events in the last eight years driven by record-high sea-surface temperatures — though large-scale restoration initiatives such as "Coral IVF" are being scaled up, according to an October 2026 overview.

Why It Matters

Reefs are not just pretty scenery. They support fish habitat, coastal protection and livelihoods linked to fishing and tourism for hundreds of millions of people, and their degradation cascades into food security and coastal economies. "El Niño doesn't add new heat to the planet. It releases heat the ocean has already been storing beneath the surface — which is why a strong event so often becomes one of the hottest years measured, as with 2024," Celeste Saulo told the Global Heat Forum in Bangkok, held October 6–9. "The ocean it's drawing from is the warmest we've ever measured it. There is simply more heat available to release."

The WMO's rainfall outlook shows the global stakes. The dominant wet signal is above-normal rainfall across the central and eastern equatorial Pacific east of the Date Line, with wetter-than-normal conditions also more likely across the Greater Horn of Africa, parts of Central Asia and coastal East Asia, northern parts of the Arabian Peninsula, parts of North America south of 45°N, and southeastern South America. In contrast, a broad dry signal is forecast over the western Pacific and the equatorial Atlantic stretching across the South Pacific to the southern tip of South America — with drier-than-normal conditions over the Indian subcontinent, southern Central America and parts of the Caribbean, and northwestern South America.

These shifts — coherent with a strong El Niño — raise the likelihood of heat extremes and heat-related impacts across large areas from October through December, and WMO and its members have mobilized meteorological services and humanitarian partners through the WMO Coordination Mechanism to help minimize impacts across all sectors of the economy.

Illustration: a stylized depiction of divers relocating coral nurseries to cooler, deeper water.

What Happens Next

• El Niño is forecast to peak around December 2026, with a near-100 percent likelihood of persisting through February 2027.
• WMO's monthly Global Seasonal Climate Updates will track whether the Niño 3.4 index reaches the forecast record of ~3.7°C above normal.
• Coral reef scientists worldwide, led by NOAA's Coral Reef Watch, will be monitoring for the onset of a fifth Global Coral Bleaching Event.
• Costa Rica's relocated 2,700 corals will be watched to see whether deeper placement improves survival through the heat peak.
• The positive Indian Ocean Dipole peaks in October and then declines, but equatorial Atlantic warmth persists — keeping tropical storm and rainfall risks elevated.
• Countries in the forecast wet and dry zones — from the Horn of Africa to the Indian subcontinent to southeastern South America — face planning decisions on flood and drought preparedness through early 2027.

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FAQ

Q: How strong is the current El Niño expected to be?

A: The WMO forecasts the Niño 3.4 sea-surface temperature index could reach about 3.7°C above normal for October–December 2026 — the highest since observations began, above the previous record of 2.6°C in late 2015 — and says it could become one of the strongest events since at least 1950, peaking around December.

Q: Why is El Niño so dangerous for coral reefs?

A: Corals are highly heat sensitive. El Niño temporarily elevates ocean temperatures on top of background warming, increasing the frequency and intensity of bleaching events. Every strong El Niño since 1998 has been linked to a Global Coral Bleaching Event.

Q: What did the UN biodiversity expert say?

A: IPBES chair David Obura called this El Niño a "terrifying" threat to coral reefs, warning it could drive vulnerable coral species even closer toward extinction — worse than the 1997/98 super El Niño, after three intervening global bleaching events.

Q: What are scientists doing to protect corals?

A: In Costa Rica, researchers moved about 2,700 corals from ~5m to 13m depth near Isla Tortuga, where cooler water may reduce heat stress, while intensifying monitoring. In Australia, "Coral IVF" — rearing millions of coral larvae in nurseries and releasing them onto damaged reef — is being scaled up.

Q: Beyond reefs, what weather impacts are expected?

A: The WMO forecasts above-average temperatures across large areas October–December, with wetter-than-normal conditions in the central/eastern Pacific, the Greater Horn of Africa and southeastern South America, and drier-than-normal conditions over the Indian subcontinent, southern Central America and the Caribbean.

Sources

• WMO / PreventionWeb (Oct 13, 2026) — Global Seasonal Climate Update: record Pacific warmth forecast, El Niño peak December, near-100% persistence through February 2027.
• WMO on LinkedIn (Oct 10, 2026) — Niño 3.4 anomalies from +1.6°C (June) to +2.5°C (August); ~+3.7°C forecast for Oct–Dec, highest since observations began.
• phys.org / AFP (Oct 15, 2026) — IPBES chair David Obura: El Niño a "terrifying" threat to coral reefs, potentially worse than 1997/98.
• NewsNation Online (Oct 17, 2026) — Costa Rica scientists move 2,700 corals from ~5m to 13m depth near Isla Tortuga as El Niño heats the Pacific.
• Mongabay via SphereNexus (Oct 10, 2026) — NOAA's Derek Manzello on four Global Coral Bleaching Events; 8.9% coral cover decline in 2023–2024.
• Citizen Daily Post (Oct 2026) — Great Barrier Reef remains off UNESCO danger list but under "serious threat"; five mass bleaching events in eight years; Coral IVF scaling up.