2025 was the second-warmest year for the South-West Pacific, according to the latest State of the Climate in the South-West Pacific 2025 report released by the World Meteorological Organization (WMO). The region recorded an average surface temperature 0.37°C above the 1991-2020 baseline, making 2025 the second-hottest year on record after 2024. Beyond rising temperatures, the report highlights a year marked by warming oceans, extensive marine heatwaves, rising sea levels, stronger tropical cyclones, and the rapid disappearance of tropical glaciers.

One of the year’s deadliest disasters was Cyclone Senyar, which affected more than 10 million people across Indonesia and Malaysia and claimed over 1,200 lives. Scientists warn these climate impacts are becoming more frequent and severe, increasing risks for ecosystems, coastal communities, fisheries, agriculture, and public health across the region.

Ocean Warming Continues at an Alarming Pace

The report shows that ocean temperatures remained exceptionally high throughout 2025 despite the presence of La Niña, which typically brings temporary cooling to parts of the Pacific.

Record-breaking ocean heat content was observed south of Australia, across the southern Tasman Sea, and in parts of the tropical North Pacific between the Philippines and Hawaii. Sea surface temperatures also reached record highs around Papua New Guinea and across much of Australia’s surrounding waters.

Scientists say warmer oceans are fueling longer-lasting and more intense marine heatwaves, which threaten coral reefs, fisheries, aquaculture, and marine biodiversity.

Marine Heatwaves Threaten Ocean Life

Although 2025 was the second-warmest year for the South-West Pacific, one of the report’s biggest concerns is the increasing frequency of marine heatwaves.

Marine heatwaves occur when ocean temperatures remain unusually high for prolonged periods. These events can trigger:

• Mass coral bleaching
• Fish mortality
• Harmful algal blooms
• Loss of kelp forests
• Declining aquaculture productivity
• Shifts in marine species distribution

The most severe marine heatwaves in 2025 occurred between the Maritime Continent and Australia, as well as across the western South Pacific near New Zealand, New Caledonia, and Vanuatu.

Australia also experienced widespread marine heatwaves during the summer of 2024-2025, leading to coral bleaching on both its eastern and western reef systems, the first time both regions were affected in the same season.

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Papua’s Last Tropical Glacier Nears Disappearance

The report also highlights the dramatic loss of tropical glacier ice in Papua, Indonesia.

Scientists estimate that only about 2% of the glacier’s ice area remains compared with 1988, making it one of the fastest-disappearing glaciers in the world.

Current projections indicate the region’s final tropical glacier could disappear completely by late 2026 or early 2027, marking the end of tropical glaciation in the South-West Pacific.

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Cyclone Senyar Leaves a Devastating Impact

Extreme weather continued to accompany rising temperatures throughout 2025.

• Cyclone Senyar, the first known tropical cyclone to reach cyclone intensity within the Strait of Malacca, became the region’s deadliest weather disaster of the year.
• The storm caused widespread destruction across Indonesia and Malaysia, affecting more than 10 million people and resulting in over 1,200 fatalities, according to the report.

Its unusual development also highlights how warming ocean temperatures may influence tropical cyclone behavior in regions that have historically experienced fewer intense storms.

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Early Warning Systems Becoming Increasingly Important

The report emphasizes that better forecasting and early warning systems are becoming essential as climate risks intensify.

Released during the Southeast Asia Marine Heatwaves Services Workshop in Singapore, the report showcases new marine heatwave forecasting services developed by the Australian Bureau of Meteorology and CSIRO. These systems provide weeks or even months of advance notice, helping governments, fisheries, coastal industries, and conservation agencies prepare for extreme ocean conditions.

The WMO stresses that timely warnings and coordinated climate services will be critical for protecting lives, ecosystems, and economies as warming continues across the South-West Pacific. With a potentially strong El Niño now developing for 2026, scientists warn that even more challenging climate conditions could lie ahead if global temperatures and ocean heat continue their upward trend.

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