Sea temperatures near record in March as El Nino odds rise: Climate agency

Global oceans stayed extraordinarily warm in March, posting the second-highest March sea-surface temperature ever recorded and brushing up against last year’s peak set during a powerful El Niño. The persistence of ocean heat is fueling concern that the world could be headed for another bout of accelerated warming.

According to Europe’s climate monitoring service, the average sea-surface temperature across the ice-free oceans between 60°S and 60°N reached 20.97°C in March. That makes it the second-warmest March in the record books, behind March 2024, when a strong El Niño helped propel temperatures to unprecedented levels. Daily readings climbed steadily through the month, edging toward last year’s extraordinary highs.

El Niño signals strengthen for 2026

Several leading climate centers now anticipate a transition from today’s neutral conditions to an El Niño state in the second half of 2026. El Niño is defined by unusually warm waters in the central and eastern equatorial Pacific. When it emerges, it commonly boosts global average temperatures on top of the long-term warming driven by greenhouse gas emissions, and can reshape weather patterns around the world.

While seasonal outlooks carry uncertainty, a return of El Niño typically raises the odds of more intense heat, disruptive rainfall shifts, and heightened risks of floods and droughts in vulnerable regions. The last major event amplified heat waves on land and in the ocean, setting off widespread marine heatwaves and contributing to coral bleaching.

Why ocean heat matters

The ocean absorbs the vast majority of the excess heat trapped by human-caused greenhouse gases. When the upper ocean warms, it can:

• Supercharge marine heatwaves that stress ecosystems, trigger coral bleaching, and disrupt fisheries.
• Alter storm behavior and rainfall patterns, influencing flood and drought risks across continents.
• Feed back into global air temperatures, increasing the likelihood of new heat records.

March’s near-record warmth underscores how little respite the oceans have had since last year. Even outside the tropics, broad swaths of the Atlantic and Pacific have been running hot, with lingering anomalies that have persisted through winter into early spring. Such background warmth means any return of El Niño could more readily push global temperatures to new milestones.

What to watch next

• Marine heatwave hotspots: Parts of the Atlantic and Pacific have hovered in heatwave territory; continued monitoring will show whether these expand into summer.
• Coral bleaching risks: Elevated temperatures raise the chance of bleaching alerts in sensitive reef regions if anomalies persist or intensify.
• Seasonal outlooks: Monthly updates on El Niño–Southern Oscillation conditions will clarify whether a shift toward El Niño in 2026 is gaining momentum.
• Extremes on land: Warmer oceans can load the dice for stronger heatwaves and erratic rainfall in many regions, compounding existing climate risks.

With March’s ocean temperatures again hovering near the top of the chart, the signal is clear: the planet’s primary heat reservoir remains abnormally warm. If El Niño does reemerge as projected, it will add another layer to that heat, raising the stakes for ecosystems, economies, and communities worldwide.