Global ocean heat has hit a new record every day for the past year

(CNN) — The world’s oceans have experienced an entire year of unprecedented heat, with a new temperature record broken every day, new data shows.

Global ocean surface temperatures began breaking daily records in mid-March last year, according to data from the National Oceanic and Atmospheric Administration (NOAA) and the University of Maine’s Climate Reanalyzer, raising concerns about life marine and extreme climate throughout the planet.

“The extent to which previous sea surface temperature records were broken in 2023, and now again in 2024, is remarkable,” said Joel Hirschi, associate head of marine systems modeling at the U.K.’s National Oceanography Centre. .

Global average ocean temperatures in 2023 were 0.25 degrees Celsius warmer than the previous year, said Gregory C. Johnson, an oceanographer at NOAA. That increase “is equivalent to about two decades of warming in a single year,” he told CNN. “So, it’s pretty big, pretty significant and a little bit surprising.”

Scientists have said ocean heat is being supercharged by human-caused global warming, driven by El Niño, a natural weather pattern marked by higher-than-average ocean temperatures.

The main consequences are for marine life and the global climate. Global heat from the oceans can add more power to hurricanes and other extreme weather events, including scorching heat waves and intense rainfall.

High ocean temperatures are already proving catastrophic for corals. Australia’s Great Barrier Reef is experiencing its seventh mass bleaching event, authorities announced in March following aerial surveys.

Bleaching occurs when heat-stressed corals release the algae that live in their tissues and provide them with their food source. If ocean temperatures remain too high for too long, coral can starve and die.

Data from NOAA’s Coral Reef Watch tool shows the problem goes far beyond Australia and the world could face a fourth global mass coral bleaching event in the coming months.

Ocean heat sets the stage for more ferocious hurricanes. “The warmer the ocean, the more energy is available to fuel storms,” ​​said Karina von Schuckmann, an oceanographer at Mercator Ocean International in France.

Temperatures have been unprecedented in the North Atlantic, a key ocean area for hurricane formation, surprising some scientists, who are still trying to unravel the exact causes.

“Records (in the North Atlantic) have sometimes been broken by margins that are virtually statistically impossible,” Brian McNoldy, a senior research associate at the University of Miami’s Rosenstiel School, told CNN.

If very high ocean temperatures continue into the second half of 2024 and a La Niña event develops – the counterpart to El Niño that tends to amplify the Atlantic hurricane season – “this would increase the risk of a hurricane season.” very active,” Hirschi said.

About 90% of the world’s excess heat produced by burning planet-warming fossil fuels is stored in the oceans. “Measuring ocean warming allows us to track the state and evolution of planetary warming,” Schuckmann told CNN. “The ocean is the sentinel of global warming.”

El Niño is weakening and is expected to dissipate in the coming months, which could level off record ocean temperatures, especially if the cooling effects of La Niña replace it.

“In the past, surface temperature values ​​decreased after the passage of El Niño,” Schuckmann said. But, he added, it is currently impossible to predict when ocean heat will fall below record levels.

While natural climate variability will cause ocean temperatures to fluctuate, in the long term, NOAA’s Johnson said, we should expect them to “continue to break records as long as greenhouse gas concentrations in the atmosphere continue to rise.”

CNN’s Derek Van Dam contributed to this report.