Storms, Acid Seas and Vanishing Ice: WMO Flags a Deepening South-West Pacific Crisis

The World Meteorological Organization’s State of the Climate in the South-West Pacific 2025 report warns that the region recorded its second-warmest year on record, with hotter and more acidic oceans, rising seas and destructive extreme weather. The findings matter because climate risks are converging across marine ecosystems, coastal communities, island nations and weather-disaster systems, raising pressure for stronger early warning, adaptation and climate-smart planning.

The South-West Pacific is entering a sharper phase of climate risk, where warming seas, rising water, ocean acidification and extreme weather are no longer separate warnings but overlapping pressures on economies, ecosystems and coastal communities. A new World Meteorological Organization (WMO) report says the region had its second-warmest year on record in 2025, behind only 2024, while Cyclone Senyar became the deadliest single event, affecting more than 10 million people in Indonesia and Malaysia and killing more than 1,200.

The South-West Pacific is not just getting warmer; its oceans are storing more heat, its waters are becoming more acidic, its seas are rising, and its weather systems are exposing gaps in disaster preparedness. For a region defined by island nations, fisheries, reefs, coastal settlements and maritime economies, the climate threat is moving from forecast to lived reality.

A region warming past its comfort zone

The WMO's State of the Climate in the South-West Pacific 2025 report places the region's annual mean surface air temperature at about 0.37°C above the 1991–2020 average, making 2025 the second-warmest year on record for land and ocean areas combined. The report also notes warmer-than-average temperatures in the western Pacific and below-average temperatures over the central tropical Pacific, a pattern typical of La Niña conditions.

La Niña can temporarily cool sea-surface temperatures in parts of the region. Yet the wider South-West Pacific average remained high, with record levels recorded over a broad area of the tropical western North Pacific, around Papua New Guinea, and in the Australia region as a whole.

The 2025 findings point to a region where natural climate variability is now operating on top of a long-term warming trend. The result is a more volatile climate baseline: even when some areas cool temporarily, the broader system remains under strain.

The retreat of Papua's tropical ice underlines how fast some physical thresholds are being crossed. In 2025, the remaining tropical ice cover in Papua, Indonesia, was estimated at only about 2% of the ice area observed in 1988, with the region's last remaining tropical glacier expected to disappear by the end of 2026 or early 2027.

The ocean is carrying the climate bill

Long-term ocean warming has made marine heatwaves more frequent, longer-lasting and more intense, with consequences for marine ecosystems and communities and industries that depend on them. In 2025, record high ocean heat content in the upper 700 metres was observed south of Australia, in the southern Tasman Sea, in parts of the tropical North Pacific between the Philippines and Hawaii, and locally south of Sumatra.

Marine heatwaves translate climate pressure into economic and ecological damage. They can cause coral bleaching, fish deaths, disruptions to aquaculture, kelp forest mortality, shifts in species distribution and harmful algal blooms. For coastal communities, this means the risk is not confined to biodiversity loss. It can affect food security, tourism, fisheries income and the stability of marine-based livelihoods.

Marine heatwave coverage in 2025, though lower than the previous year, was the most extensive ever recorded in a year without an El Niño event. The report describes this as a worrisome sign for 2026, with a potentially strong El Niño event developing.

Australia's reefs show how quickly marine heat can become a visible crisis. During summer 2024–2025, extensive marine heatwave conditions affected northern Australia, the west coast, the Great Australian Bight and southern waters. This contributed to coral bleaching in both eastern and western reef systems in the same season for the first time.

Rising seas are shrinking the safety margin

Sea-level rise is the slower-moving threat, but it may be the most unforgiving for low-lying communities. Between 1999 and 2025, sea level rose at an average rate of 3.7 ± 0.03 mm per year in the South-West Pacific. Higher rates were observed in an elongated pattern from the eastern coast of Australia to about 120°W longitude, covering the Coral and Tasman Seas and a large area west of New Zealand.

For coastal communities and low-lying island nations, rising seas raise the stakes of every storm, flood and coastal erosion event. They also complicate long-term planning for housing, transport, ports, freshwater systems and coastal infrastructure. The challenge is not only protecting people during disasters, but deciding where and how communities can safely live, work and invest in the decades ahead.

Ocean acidification adds another layer of risk. As oceans absorb increasing amounts of carbon dioxide, waters become more acidic, affecting marine ecosystems, habitats and biodiversity. In 2025, almost the entire South-West Pacific experienced record low values for surface ocean pH.

Together, warming, acidification and sea-level rise are narrowing the region's margin for adaptation. A reef damaged by heat may also face more acidic waters. A coastal settlement threatened by rising seas may also face stronger rainfall, flooding or storm surge. The danger is cumulative, and that makes climate-smart planning harder but more urgent.

Cyclone Senyar exposed the last-mile warning gap

Extreme weather gave the region its most immediate human toll in 2025. Several countries experienced climate events with fatalities and significant economic losses, especially from tropical cyclones. Cyclone Senyar was the first tropical cyclone on record in the Strait of Malacca since 1886, making landfall in northern Sumatra on 26 November before crossing the Strait and making a second landfall over Peninsular Malaysia. The heaviest rainfall included more than 400 mm in one day in far northern Sumatra, with extreme rainfall also affecting northern Peninsular Malaysia and southern Thailand.

Senyar demonstrated both progress and vulnerability. Early warnings, collaboration and local grants helped reduce casualties and support rapid relief, but gaps remained in last-mile warning dissemination to some coastal populations and fishers. That is a critical lesson for disaster risk reduction: better forecasts do not save lives unless they reach the people most exposed, in time, in language they understand and through channels they trust.

The next frontier is impact-based forecasting for cascading hazards. Senyar showed the need to prepare for complex scenarios where cyclonic storms combine with monsoon surges to trigger floods, landslides and debris flows, and may even coincide with geophysical hazards such as earthquakes or tsunamis.

For the South-West Pacific, climate risk is no longer a distant oceanic signal measured only by scientists. It is arriving through bleached reefs, rising seas, disappearing ice, damaged livelihoods and storms that test whether warnings can reach the last mile. The region's next climate challenge is not just to measure the danger more accurately, but to turn that knowledge into faster protection for the people and ecosystems already in its path.