The ocean across the Southwest Pacific region is becoming hotter and more acidic, harming local economies and marine ecosystems, while rising sea levels threaten vulnerable coastal communities and low-lying island nations, according to a new report from the World Meteorological Organization (WMO).
The State of the Climate in the South-West Pacific 2025 report found the region had its second warmest year on record, behind 2024, with extreme weather causing widespread disruption, economic damage and loss of life. The deadliest single event was Cyclone Senyar in November 2025, the first known system to reach tropical cyclone intensity in the Strait of Malacca, which affected more than 10 million people in Indonesia and Malaysia and killed more than 1,200.
The remaining tropical ice cover in Papua, Indonesia, was estimated in 2025 to be only about 2% of the ice area observed in 1988. The report projects the region’s last remaining tropical glacier will disappear by the end of 2026 or early 2027.
WMO secretary-general Celeste Saulo said the ocean is central to livelihoods, economies and resilience across much of the region: “In 2025, the region experienced warming oceans, rising sea levels, marine heatwaves and ocean acidification, alongside tropical cyclones and the continued loss of tropical glacier ice.”
Armida Salsiah Alisjahbana, executive secretary of the UN Economic and Social Commission for Asia and the Pacific, said heat is intensifying multi-hazard risks across the region: “Early warning and early action save lives when alerts are timely, messages are trusted and last-mile delivery reaches the vulnerable.”
The annual mean surface air temperature across the region in 2025 ranked as the second highest on record, about 0.37°C above the 1991–2020 average, with warmer-than-average conditions in the western Pacific and below-average temperatures in the central tropical Pacific, typical of La Niña.
Marine heatwave coverage in 2025, while lower than the previous year, was the most extensive ever recorded in a year without an El Niño event – a trend the report calls concerning given a potentially strong El Niño now developing for 2026. The most severe and extensive heatwaves occurred between the Maritime Continent and Australia, and in waters between New Zealand, New Caledonia and Vanuatu, contributing to coral bleaching in both eastern and western Australian reef systems in the same season for the first time on record.
Sea level in the region rose at an average rate of around 3.7mm per year between 1999 and 2025, with the highest rates recorded from eastern Australia to around 120°W, spanning the Coral and Tasman Seas. Nearly the entire region also recorded record-low surface ocean pH values in 2025.
The report was released at the Southeast Asia Marine Heatwaves Services Workshop in Singapore, running July 7–10, organized by the ASEAN Specialised Meteorological Centre.
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