Earth’s oceans absorbed unprecedented heat last year, intensifying hurricanes, floods and droughts while driving sea levels higher.
By Jeremy Yurow, Courthouse News Service
The world’s oceans absorbed more heat in 2025 than any year on record, providing the fuel for extreme weather that killed thousands of people across the globe, according to researchers of a study published Friday in Advances in Atmospheric Sciences.
The amount of heat the oceans soaked up last year is difficult to comprehend: 23 zettajoules more than 2024. That’s roughly the same amount of energy the entire world uses in 37 years.
Think of it this way: If you took every power plant, every car, every light bulb, and every device on Earth and ran them continuously for 37 years, that’s how much extra heat the oceans absorbed in just 2025 alone.
“The ocean absorbs more than 90% of the excess heat trapped by greenhouse gases, making it the main heat reservoir of the climate system,” wrote the researchers, a team of more than 50 scientists from 31 institutions across Asia, Europe and the Americas.
The study found that 2025 marks the ninth straight year of record-breaking ocean heat. The researchers analyzed data from major monitoring centers, including the Chinese Academy of Sciences, Copernicus Marine and NOAA, to ensure their findings were accurate.
The consequences were tragic and far-reaching. In Southeast Asia, intense monsoon rains triggered catastrophic flooding in July, with some regions receiving over 31 inches of rainfall over just five days. Floods killed more than 1,350 people in Indonesia, Sri Lanka, Thailand and Vietnam in November.
In the United States, a flash flood in Central Texas over the Fourth of July weekend killed at least 138 people. The record-breaking rainfall highlighted what scientists call “the escalating risks associated with rapidly intensifying storm systems in a warming climate.”
These disasters are connected to warming oceans in a direct way. Warmer water means more evaporation, which puts more moisture into the air. When storms form over these supercharged oceans, they carry that extra water and dump it as extreme rainfall.
The warming isn’t happening evenly everywhere. About 14% of the world’s oceans hit their highest temperatures ever recorded in 2025, while roughly one-third ranked among the top three warmest years in their historical records. The tropical and South Atlantic Ocean, Mediterranean Sea, North Indian Ocean and Southern Ocean saw the most intense warming.
The Mediterranean Sea, North Atlantic and Southern Ocean all hit record-high temperatures in 2025. In the Mediterranean, the researchers found continued warming of intermediate waters, with temperatures reaching the highest levels on record. Nearly half of the Southern Ocean (the waters surrounding Antarctica) reached its highest temperature on record.
Other regions experienced dramatic changes as well. Central China experienced severe mountain floods and landslides in July, forcing large-scale evacuations and causing substantial infrastructure damage. Nigeria and neighboring West African regions suffered damaging flash floods that displaced thousands.
In western and southern Europe, a persistent summer heat dome drove temperatures above 118 degrees Fahrenheit and fueled extensive wildfires.
Lijing Cheng, the study’s lead author from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, explained the cover art for the journal’s special issue: cartoon images of sad, distressed shrimp and crabs inspired by characters from the classic Chinese novel “Journey to the West.”
“We reimagined them not as mighty guardians, but as vulnerable creatures whose armor, their shells and scales, is under attack by ocean warming, acidification and other ocean environmental changes,” Cheng said.
Climate scientist Kevin Trenberth said that as long as humans continue pumping greenhouse gases into the atmosphere, the oceans will keep absorbing heat, records will keep falling, and extreme weather will keep intensifying.
“The biggest climate uncertainty is what humans decide to do,” Trenberth said. “Together, we can reduce emissions, better prepare for upcoming changes, and help safeguard a future climate where humans can thrive.”
