A study published in Advances in Atmospheric Sciences has found that ocean warming in 2024 has led to new record high temperatures. The ocean is the hottest it has ever been recorded by humans, not only at the surface temperature but also for the upper 2000 meters.
“The broken records in the ocean have become a broken record,” said Prof. Lijing Cheng with the Institute of Atmospheric Physics at the Chinese Academy of Sciences. He led a team of 54 scientists from seven countries and discussed how a hotter ocean affects our lives on land and what this means for our future.
Why is the ocean so important?
The ocean is a critical part of the Earth’s climate—most of the excess heat from global warming is stored in the ocean (90%) and the ocean covers 70% of the Earth’s surface. Because of this, the ocean dictates our weather patterns by transferring heat and moisture into the atmosphere. The ocean also controls how fast climate change happens.
“To know what is happening to the climate, the answer is in the ocean,” said Prof. John Abraham at the University of St. Thomas, co-author of the study.
The image shows one set of results for the upper 2000 m ocean heat content (from the Institute of Atmospheric Physics). Blue and red colors refer, respectively, to whether a particular year was colder or hotter than the 1981–2010 period. This time period is used as a basis for scientists to compare against reference conditions. The central message is that the values have been increasing year after year after year.Ocean heat content changes for the upper 2000 meters of ocean waters, since 1958. Green bars indicate the measurement accuracy. © Cheng et al.
Results from three international teams who collaborated on this project were consistent—the ocean is warming, and 2024 was a record.
From 2023 to 2024, the global upper 2000 m ocean heat content increase is 16 zettajoules (1021 Joules), ~140 times the world’s total electricity generation in 2023.
“OHC has increased steadily by 15–20 ZJ over the past five years despite the La Niña and El Niño cycles,” said Prof. Michael Mann from the University of Pennsylvania.
The ocean surface temperature is also setting records. The surface temperature refers to temperatures just at the surface, where the ocean waters and atmosphere commute. Surface temperatures are important because they dictate how fast heat and moisture (humidity) can transfer from the ocean to the air and thus affect weather. The rise in surface temperatures since the late 1950s has been staggering.
Why does this matter?
The changes are not uniform; regional variations can be substantial. The Atlantic is warming along with the Mediterranean Sea, and across the mid-latitude Southern Ocean. While parts of the Northern Pacific Ocean have warmed very rapidly, other areas (the tropical region) have not, mostly due to the La Niña/El Niño cycle in that area. The heat has even accumulated near both the North and South Poles.
The ocean warming patterns are not uniform; regional variations can be substantial. © Cheng et al.
The ocean surface temperature is also setting records. © Cheng et al.
A warmer ocean affects marine life and results in huge damage in many ways.
“The main way the ocean continues to influence the climate is through accompanying increases in water vapor in the atmosphere that leads to the damaging increases in extremes in the hydrological cycle,” said Dr. Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research, U.S., another member of the team.
“Water vapor is also a powerful greenhouse gas and increased heating leads to drying and risk of drought and wildfire. But it also fuels storms of all sorts and leads to risk of flooding. That includes hurricanes and typhoons.”
For example, over the past 12 months, a staggering 104 countries have recorded their hottest temperatures ever. Droughts, heat waves, floods, and wildfires have impacted Africa, Southern Asia, the Philippines, Brazil, Europe, the U.S., Chile, and the Great Barrier Reef, as just but a few examples. Since 1980, for example, climate disasters have cost the U.S. nearly $3 trillion.
The heat in the ocean is the best measurement for monitoring the changing climate. “The ocean is our sentinel for planetary warming, acting as the major sink of surplus heat accumulating in the Earth’s climate system as a result of anthropogenic emissions,” said Dr. Karina von Schuckmann at Mercator Ocean International, co-author of the study.
If there continues to be a failure to take action to slow climate change, the disruption, unprecedented change and its implications, costs and loss and damage will continue to increase.
More information:
Sea Surface Temperatures and Deeper Water Temperatures Reached a New Record High in 2024, Advances in Atmospheric Sciences (2025). DOI: 10.1007/s00376-025-4541-3
Provided by
Chinese Academy of Sciences
Citation:
Ocean temperatures hit record highs in 2024, study finds (2025, January 10)
