The research, led by Lijing Cheng from the Institute of Atmospheric Physics at the Chinese Academy of Sciences along with 54 scientists from seven countries, found new temperature records in six of eight investigated ocean regions: the Indian Ocean, tropical Atlantic, Mediterranean Sea, North Atlantic, North Pacific, and Southern Ocean.
The global sea surface temperature (SST) continued its record-high trajectory from 2023 into the first half of 2024, showing a slight decline in the second half of the year in response to increased greenhouse gas concentrations in the atmosphere. The 2024 annual mean global SST surpassed the previous year’s record by 0.05°C–0.07°C, establishing a new high for the instrumentation era.
“The broken records in the ocean have become a broken record,” said Cheng, while co-author, professor John Abraham at the University of St. Thomas, emphasised, “To know what is happening to the climate, the answer is in the ocean.”
Professor Michael Mann from University of Pennsylvania noted, “Ocean Heat Content has increased steadily by 15~20 ZJ over the past five years despite the La Niña and El Niño cycles.”
The implications are extensive. Ocean warming accounts for more than one-third of global mean sea level rise through thermal expansion. The warming is exacerbating extreme weather events, including intensification of typhoons, hurricanes, and marine heatwaves.
The extra heat and moisture entering the atmosphere make storms more severe, with heavier rain, stronger winds, and more significant flooding. The study found that warming leads to more rapid intensification of storms and slower decay after landfall, increasing flooding risks related to tropical cyclones.
The warming is also causing ocean deoxygenation, creating significant hazards for marine life, ecosystems, humans, and terrestrial ecosystems. “The ocean is our sentinel for planetary warming, acting as the major sink of surplus heat accumulating in Earth climate system as a result of anthropogenic emissions,” said Dr. Karina von Schuckmann at Mercator Ocean International.
These findings align with broader climate trends. WMO Secretary-General Celeste Saulo noted, “Climate history is playing out before our eyes. We’ve had not just one or two record-breaking years, but a full ten-year series. This has been accompanied by devastating and extreme weather, rising sea levels and melting ice, all powered by record-breaking greenhouse gas levels due to human activities.”
The impact is already visible in places like Lakshadweep, where heat stress reached record levels in 2024. Local fisherman Anwar Hussain from Kavaratti told HT earlier, “The temperature of the deeper outer lagoon was 32 degrees C, but the surface water in the shallow lagoon was even warmer, around 36 degrees C, during the peak heating period in April and May. How can corals survive that heat?”
According to Derek P Manzello, coordinator of NOAA Coral Reef Watch, the heat stress in Lakshadweep (Laccadive Sea) and in southeastern India was record-setting in 2024.
The findings come as human-induced climate change remains the primary driver of extreme air and sea surface temperatures, while other factors, such as the El Niño Southern Oscillation (ENSO), also contributed to the unusual temperatures observed during the year.
UN Secretary-General António Guterres emphasised this urgency: “Individual years pushing past the 1.5 degree C limit do not mean the long-term goal is shot. It means we need to fight even harder to get on track. Blazing temperatures in 2024 require trail-blazing climate action in 2025.”
