During cyclone Ditwah Sri Lanka received 10% of its yearly rainfall in a single day.Credit: © Cyrielle Beaubois/Getty
The amount of heat stored in oceans in Asia reached the highest level on record last year, according to the World Meteorological Organization. Ocean heat has risen sharply in the region since the 1990s, destabilizing ocean currents and marine life and driving up sea levels.
The annual State of the Climate in Asia report, released today, found that in 2025, ocean heat content — the amount of heat stored down to a depth of 700 metres — was around 700 million joules per square metre higher than the 1991–2020 average.
Almost all of Asia’s oceans, including the Indian Ocean, Western Pacific, parts of Arctic Ocean and the inland Caspian Sea, experienced periods of extreme heat last year, called a marine heatwave. This is alarming because so much of the region experienced heatwaves at the same time, says Jodie Rummer, a marine biologist at James Cook University in Townsville, Australia.
Sea levels also hit record highs, caused by the combination of ocean warming and melting glaciers, ice caps and ice sheets. Across coastal areas of the northern Indian Ocean, between the Philippines and Japan, sea levels rose faster than the global average.
The region is particularly sensitive to rising sea levels because of the trade winds that blow across the Pacific Ocean from the Americas, which push warmer waters towards Asia, says Matthew England, who studies oceanography at UNSW Sydney in Australia. As this water accumulates in the Western Pacific, it pushes up both the water temperature and sea levels, England says.
“The report clearly shows that the Asian region is one of the most vulnerable to climate change,” he adds.
What’s to come?
A major driver of climate last year was the La Niña weather pattern, the report authors say. During these patterns, ocean temperatures in Asia are unusually warm and the trade winds are particularly strong, pushing even more warm water into Asia.
But the pattern is shifting. On Tuesday, Australia’s Bureau of Meteorology announced that the opposite weather pattern, El Niño, has now begun. The US National Oceanic and Atmospheric Administration issued its own El Niño advisory on 11 June. During El Niño, ocean temperatures are higher than usual in the Pacific.
In southeast Asia, El Niño will lead to drier conditions, causing drought and increasing the chance of wildfires, says Andrew King, a climate scientist at the University of Melbourne in Australia. Together, the effects of climate change and El Niño could lead to particularly extreme weather events in the coming year, he says.
Extreme weather
The report notes that countries in Asia experienced multiple extreme weather events last year, including monsoons, tropical cyclones, heatwaves and drought.
The monsoon season delivered exceptionally heavy rainfall in Pakistan, leading to floods that killed more than 1,000 people. Extreme rainfall in Sri Lanka, brought by cyclone Ditwah, saw the country receive 10% of its annual rainfall in 24 hours. The Macao region in China experienced 14 tropical-cyclone impacts during the year — the most recorded in a single year.
