Global Ocean Temperatures Near Record High as 2026 Spike Arrives Without El Niño Boost

On March 31, the surface of the world’s oceans averaged about 21.1°C (70°F)—one of the highest values ever recorded and just a fraction below the all-time record set two years ago—according to preliminary analyses from major climate monitoring centers.

Data from the University of Maine’s Climate Reanalyzer, which visualizes a National Oceanic and Atmospheric Administration sea surface temperature dataset, put the global average that day at 21.12°C. That is 0.57°C above the 1991–2020 average and only 0.04°C below the late-March 2024 peak of 21.16°C, the modern record.

The European Union’s Copernicus Marine Service, which uses a separate reanalysis based on the ERA5 climate dataset, similarly reported that global sea surface temperatures at the end of March were “just over 21°C” and around 0.5°C warmer than its 1993–2022 baseline. Copernicus scientists say March 2026 is on track to be the second-warmest March for the global ocean, behind only March 2024.

A record-threat without the usual El Niño driver

What stands out to researchers is not only how close 2026 has come to the previous record, but the backdrop against which it is happening. Rather than being driven by a strong El Niño event, which typically pushes global temperatures higher, this year’s spike is occurring as the climate system transitions away from a weak La Niña into neutral conditions in the tropical Pacific.

“We are at an exceptionally high global temperature level, very close to the records of 2024, within a few hundredths of a degree,” oceanographer Thibault Guinaldo of the French weather service Météo-France said in an interview with Le Monde. He added that ocean basins “inherit the temperatures they have experienced previously,” a reference to the ocean’s tendency to store and slowly release heat over time.

Scientists say that tendency—known as thermal inertia—is now combining with decades of greenhouse gas emissions to produce a new kind of baseline: even in years without a powerful El Niño, the world’s oceans are hovering near record warmth.

Global sea surface temperatures have been rising by roughly 0.13°C per decade since the early 1980s, according to long-term analyses by the Copernicus Climate Change Service and other groups. From April 2023 to March 2024, the ocean surface broke records month after month, contributing to 2024 becoming the hottest year in the instrumental record for global air temperatures.

The ocean as Earth’s main heat reservoir

More than 90% of the excess heat trapped by human-caused greenhouse gas emissions is absorbed by the ocean, a point emphasized by Karina von Schuckmann, a senior oceanographer at Mercator Ocean International, which operates the Copernicus Marine Service.

“Most of the excess heat in the Earth system is stored in the ocean,” von Schuckmann has said in recent assessments of the global heat budget. Natural climate variations such as El Niño and La Niña, she added, “add to the global change due to human greenhouse gas emissions,” rather than cancelling it out.

The latest numbers show that the ocean’s surface has scarcely cooled from the extreme levels reached in 2023 and 2024, even as the El Niño of that period faded and a weak La Niña briefly emerged.

Marine heatwaves spread across multiple basins

Satellite and model-based bulletins show vast swaths of the ocean locked in marine heatwaves—discrete episodes when sea surface temperatures remain unusually high for days to months.

A late-March bulletin from Mercator Ocean identified strong to severe marine heatwaves in the North Pacific, including off the coast of California and in a large patch of open ocean around 50° north. Another strong to severe event was ongoing off Angola and Namibia in the South Atlantic. The Southern Ocean between roughly 50° and 110° east longitude was also experiencing persistent warm anomalies, while the Mediterranean—which has endured repeated heatwaves in recent summers—remained warmer than average.

Some of the most pronounced anomalies at the end of March appeared in the Gulf of Mexico and parts of the tropical oceans, regions that play a central role in fueling hurricanes.

What near-record warmth could mean for hurricane season

Warmer water generally increases the potential intensity of tropical cyclones by providing more heat and moisture to developing storms. With the official Atlantic hurricane season still weeks away, forecasters caution that many factors will determine how active 2026 becomes, including wind shear and atmospheric circulation patterns over the Atlantic.

The current outlook from the National Oceanic and Atmospheric Administration and the World Meteorological Organization favors neutral conditions in the tropical Pacific through midyear, with the odds of El Niño rising later in 2026. Neutral or La Niña conditions tend to allow more Atlantic storms by reducing disruptive winds aloft, whereas El Niño often suppresses Atlantic activity even when sea surface temperatures are high.

If Atlantic waters remain significantly warmer than average while the atmosphere stays in a neutral pattern, “the background state would favor at least normal or above-normal activity,” said one U.S. seasonal forecaster in a recent television interview. A strong El Niño developing by late summer or fall, by contrast, could counter some of that potential by increasing wind shear over the basin.

In the eastern and central Pacific, the calculus is reversed. A developing El Niño later this year would tend to energize hurricanes in those basins and influence typhoon behavior in the western Pacific.

Coral bleaching and ecosystem disruption

Beyond storm counts, scientists say the near-record ocean warmth is already reshaping marine ecosystems.

The planet is in the midst of its fourth documented global coral bleaching event, which began in 2023 and by early 2025 had exposed around 84% of the world’s coral reef area to heat stress levels associated with bleaching, according to NOAA’s Coral Reef Watch program and international reef monitoring networks. Bleaching occurs when corals, stressed by heat, expel the symbiotic algae they rely on for food and color. If high temperatures persist, large areas of reef can die.

Australia’s Great Barrier Reef has endured multiple mass bleaching events since 2016. Recent government and scientific reports describe the largest annual loss of coral cover in nearly four decades during the 2023–24 and 2024–25 summers, as successive heatwaves struck before the ecosystem could recover.

Elsewhere, from the western Indian Ocean to the Caribbean and the eastern Pacific, reef systems have faced repeated bouts of extreme sea surface temperatures. The French overseas department of Mayotte, in the Indian Ocean, is among the locations highlighted by researchers as particularly exposed to recurring marine heatwaves.

Near-record global averages this year raise fears that the bleaching emergency could extend or intensify. NOAA recently expanded its bleaching alert scale after parts of the tropical ocean exceeded previous maximum categories of heat stress.

Marine ecologists warn that the impacts go far beyond coral.

“Extreme warm years and marine heatwaves can temporarily benefit some species, but overall we see a large-scale decline in fish biomass,” said Shahar Chaikin, a researcher at the Spanish National Museum of Natural Sciences, in comments reported by European media. Changes in water temperature can disrupt spawning, growth and food webs, driving some species poleward and leaving traditional fishing grounds depleted.

In the Mediterranean Sea, scientists have reported die-offs of cold-water species such as gorgonian corals during repeated heatwaves since 2022, likening the cumulative stress to experiencing a forest fire every year. At the same time, warmer conditions are favoring more tropical species, altering the makeup of ecosystems on which local fisheries and tourism depend.

Feedbacks that reach beyond the sea

As surface waters warm, they also tend to become more stratified—layered over cooler, denser water below. That makes it harder for heat and nutrients to mix downward and upward, respectively, which can further amplify surface warming while reducing productivity in some regions. Warmer water also absorbs less carbon dioxide, potentially weakening one of the planet’s most important natural carbon sinks.

The changes in the ocean reverberate through the atmosphere. The unprecedented ocean warmth of 2023 and 2024 was closely linked to a string of global air temperature records, intense heatwaves on land and increasingly heavy rainfall events in many parts of the world. Studies published in recent months suggest that, after factoring out known natural influences, the rate of global warming has accelerated over the past decade.

In the Arctic, sea surface temperatures have risen several degrees since the 1980s, contributing to thinner, younger sea ice and altered weather patterns. Around Antarctica, sea ice has remained at unusually low extents since 2016, with 2023 setting a new record minimum. Continued ocean heat uptake contributes to global sea level rise through both thermal expansion and the melting of marine-terminating glaciers.

Scientists are now watching closely to see whether the ocean’s surface temperatures in 2026 remain near record levels, dip modestly, or push into new territory—and how they will interact with whatever pattern emerges in the tropical Pacific later this year.

For coastal communities, fishers and small island states, those are not abstract questions. Coral reefs that buffer shorelines from waves are eroding, storm surge risks are increasing as seas rise and storms tap into warmer waters, and staple fisheries are shifting away.

Guinaldo, the French oceanographer, argued that the planet’s largest heat reservoir is sending an unambiguous signal.

“The basins inherit the temperatures they have experienced previously,” he said. The near-record warmth of March 2026 suggests that, for the foreseeable future, the ocean is inheriting a hotter and hotter past—and passing more of that heat back into the climate system humans depend on.