Ocean Heat and Extreme Weather: Why Today’s Climate Extremes Are Connected

Scientists are already observing clear shifts, not only in how often cyclones form, but in how they behave. Storms are intensifying more rapidly, carrying more moisture, and in some cases lingering for longer. The Intergovernmental Panel on Climate Change has found that, in a warmer world, tropical cyclones are expected to bring heavier rainfall, while NOAA’s Geophysical Fluid Dynamics Laboratory concludes that global tropical cyclone intensity and rainfall rates are likely to increase as warming continues. The result is a new kind of cyclone risk: harder to predict, and often far more destructive.

This year, that risk is being shaped by another powerful climate driver: El Niño. In June 2026, the World Meteorological Organization warned that El Niño conditions were developing in the tropical Pacific, fuelled by unusually warm ocean waters, with a high likelihood of influencing global temperature and rainfall patterns in the months ahead. El Niño is a natural climate pattern, but it is now unfolding against the backdrop of human-driven warming, meaning its impacts are layered on top of an already hotter atmosphere and ocean.

A double whammy: heatwaves and storms

One of the more worrying developments is the role of marine heatwaves (periods of unusually high ocean temperatures) in amplifying the impact of cyclones. When a storm passes over waters already warmed by a marine heatwave, the damage it causes can increase dramatically. These heatwaves effectively act as an extra energy source, allowing storms to build more rapidly and release heavier rainfall when they reach land. Recent research reported by Carbon Brief found that rapidly intensifying tropical cyclones that pass through marine heatwaves can cause around 93% greater economic damage than comparable storms that do not, even after accounting for coastal development.

The recent heatwave in Europe is a reminder that this is not only a tropical issue. Copernicus reported an exceptionally early and intense heatwave across western Europe in May 2026, followed by further warming of surrounding seas during the late-June heatwave. By 29 June, parts of the western Mediterranean were around 6°C above the long-term average, with notable warming also in the Ligurian, Tyrrhenian, southern North Sea and Baltic seas. These warmer seas do not create tropical cyclones in Europe in the same way as in the tropics, but they do show how quickly marine heat can build up around coastlines.

Cyclone impact at Ningaloo Reef

A striking recent example comes from Western Australia, where Tropical Cyclone Narelle passed near Ningaloo Reef at a particularly sensitive moment. Ningaloo is famous for its coral spawning, a remarkable natural event when corals release eggs and sperm into the water in a carefully timed and delicate mass reproduction.

This year, that timing collided with disaster. The cyclone hit during the reef’s first spawning event since the record-breaking marine heatwave of 2025, when the ecosystem was already under severe stress. Powerful waves and heavy swell tore across the reef, raising fears that many coral larvae may have been swept away before they had the chance to settle and grow.

In the storm’s aftermath, large numbers of dead animals (including fish, sea snakes, turtle hatchlings, and marine mammals) were found washed ashore. For researchers, this combination is deeply concerning: a reef weakened by heat, hit by a powerful storm at a critical moment in its recovery. As oceans continue to warm, these overlapping pressures are likely to become more common, making it increasingly difficult for reefs like Ningaloo to bounce back.

What is happening at Ningaloo also speaks to the bigger picture. Marine heatwaves, coral bleaching, cyclone damage and disrupted reproduction are not isolated problems. They can overlap in time, each one reducing the ability of an ecosystem to recover from the next. That is why the timing of storms matters so much. A cyclone striking a healthy reef is damaging; a cyclone striking a heat-stressed reef during coral spawning can interrupt the very process that would otherwise help that reef recover.

Stronger storms, longer impacts

Ningaloo is one example of a much broader concern: as storms become more intense, their impacts on marine ecosystems can also become more complex and harder to recover from. One of the more concerning observations is that some cyclones appear to be slowing down or stalling for longer in certain regions. While this pattern is not yet equally clear everywhere, and the reasons behind it are still being studied, the implications are serious.

When a storm lingers, marine life is exposed for longer to powerful waves, heavy rainfall, flooding, sediment runoff and sudden changes in water quality. Prolonged wave action can break apart coral, disturb seagrass beds and damage habitats that young fish, turtles and other species depend on. Heavy rainfall can also wash sediment, nutrients, chemicals and other pollutants from land into the sea, placing additional stress on ecosystems already weakened by heat.

These risks are also shaped by larger climate patterns, including El Niño. El Niño does not affect every region in the same way, and it does not determine the outcome of any single storm. But it can shift rainfall, heat and cyclone conditions across large parts of the world. The WMO’s July-September 2026 seasonal outlook points to a rapid development into a strong El Niño and forecasts above-normal temperatures over much of the globe, including parts of the Southern Hemisphere such as southern Africa, parts of South America and New Zealand.

That does not mean we can already predict exactly what the coming Southern Hemisphere summer will look like. But if El Niño conditions persist into late 2026, they could influence the background conditions heading into the Southern Hemisphere cyclone season, which in the Australian region officially runs from November to April.

For coastal communities around the world, these changes are no longer abstract. They are already being paid for in flooded homes, damaged harbours, lost income and slower recovery after each storm. Events once seen as rare are happening more often, and each one leaves a bigger bill behind. Ecosystems that local economies depend on, from coral reefs to fisheries, can take years to recover, if they recover at all. In many places, the question is no longer whether another storm will come, but how much damage it will leave behind.

A storm warning we can’t ignore

Cyclones have always been part of Earth’s natural climate system, but the conditions that shape them are changing rapidly. The ocean has absorbed most of the excess heat trapped by greenhouse gases, and that heat does not simply stay hidden below the surface. As the ocean warms, it changes the conditions in which storms form and intensify, providing them with more energy and moisture. But the concern is not only stronger storms. It is also what those storms now encounter: marine ecosystems already weakened by warming seas, marine heatwaves, coral bleaching, pollution, overfishing and habitat loss. In that context, a cyclone is not an isolated disturbance, but another shock to systems already struggling to recover.

The heatwave in Europe, the return of El Niño, and the damage at Ningaloo are all different parts of the same warning signs. They show how excess heat is moving through the climate system: into the atmosphere, into the ocean, into weather extremes and into the ecosystems people depend on. For the Southern Hemisphere, the coming months will need close attention, especially where warm seas, cyclone exposure and vulnerable marine ecosystems overlap.

Understanding these connections is important, because while we cannot stop storms from forming, we can still influence the conditions that make them more dangerous. That means drastically cutting greenhouse gas emissions, creating and properly managing protected ocean areas, and reducing the other pressures we place on the ocean. The warmer and more damaged the ocean becomes, the more we load the dice in favour of stronger, more damaging extreme conditions.