Tropical cyclones that rapidly intensify when passing over marine heatwaves can become “supercharged”, increasing the likelihood of high economic losses, a new study finds.

Such storms also have higher rates of rainfall and higher maximum windspeeds, according to the research.

The study, published in Science Advances, looks at the economic damages caused by nearly 800 tropical cyclones that occurred around the world between 1981 and 2023.

It finds that rapidly intensifying tropical cyclones that pass near abnormally warm parts of the ocean produce nearly double – 93% – the economic damages as storms that do not, even when levels of coastal development are taken into account.

One researcher, who was not involved in the study, tells Carbon Brief that the new analysis is a “step forward in understanding how we can better refine our predictions of what might happen in the future” in an increasingly warm world.

As marine heatwaves are projected to become more frequent under future climate change, the authors say that the interactions between storms and these heatwaves “should be given greater consideration in future strategies for climate adaptation and climate preparedness”.

‘Rapid intensification’

Tropical cyclones are rapidly rotating storm systems that form over warm ocean waters, characterised by low pressure at their cores and sustained winds that can reach more than 120 kilometres per hour.

The term “tropical cyclones” encompasses hurricanes, cyclones and typhoons, which are named as such depending on which ocean basin they occur in.

When they make landfall, these storms can cause major damage. They accounted for six of the top 10 disasters between 1900 and 2024 in terms of economic loss, according to the insurance company Aon’s 2025 climate catastrophe insight report.

These economic losses are largely caused by high wind speeds, large amounts of rainfall and damaging storm surges.

Storms can become particularly dangerous through a process called “rapid intensification”.

Rapid intensification is when a storm strengthens considerably in a short period of time. It is defined as an increase in sustained wind speed of at least 30 knots (around 55 kilometres per hour) in a 24-hour period.

There are several factors that can lead to rapid intensification, including warm ocean temperatures, high humidity and low vertical “wind shear” – meaning that the wind speeds higher up in the atmosphere are very similar to the wind speeds near the surface.

Rapid intensification has become more common since the 1980s and is projected to become even more frequent in the future with continued warming. (Although there is uncertainty as to how climate change will impact the frequency of tropical cyclones, the increase in strength and intensification is more clear.)

Marine heatwaves are another type of extreme event that are becoming more frequent due to recent warming. Like their atmospheric counterparts, marine heatwaves are periods of abnormally high ocean temperatures.

Previous research has shown that these marine heatwaves can contribute to a cyclone undergoing rapid intensification. This is because the warm ocean water acts as a “fuel” for a storm, says Dr Hamed Moftakhari, an associate professor of civil engineering at the University of Alabama who was one of the authors of the new study. He explains:

“The entire strength of the tropical cyclone [depends on] how hot the [ocean] surface is. Marine heatwave means we have an abundance of hot water that is like a gas [petrol] station. As you move over that, it’s going to supercharge you.”

However, the authors say, there is no global assessment of how rapid intensification and marine heatwaves interact – or how they contribute to economic damages.

Using the International Best Track Archive for Climate Stewardship (IBTrACS) – a database of tropical cyclone paths and intensities – the researchers identify 1,600 storms that made landfall during the 1981-2023 period, out of a total of 3,464 events.

Of these 1,600 storms, they were able to match 789 individual, land-falling cyclones with economic loss data from the Emergency Events Database (EM-DAT) and other official sources.

Then, using the IBTrACS storm data and ocean-temperature data from the European Centre for Medium-Range Weather Forecasts, the researchers classify each cyclone by whether or not it underwent rapid intensification and if it passed near a recent marine heatwave event before making landfall.

The researchers find that there is a “modest” rise in the number of marine heatwave-influenced tropical cyclones globally since 1981, but with significant regional variations. In particular, they say, there are “clear” upward trends in the north Atlantic Ocean, the north Indian Ocean and the northern hemisphere basin of the eastern Pacific Ocean.

‘Storm characteristics’

The researchers find substantial differences in the characteristics of tropical cyclones that experience rapid intensification and those that do not, as well as between rapidly intensifying storms that occur with marine heatwaves and those that occur without them.

For example, tropical cyclones that do not experience rapid intensification have, on average, maximum wind speeds of around 40 knots (74km/hr), whereas storms that rapidly intensify have an average maximum wind speed of nearly 80 knots (148km/hr).

Of the rapidly intensifying storms, those that are influenced by marine heatwaves maintain higher wind speeds during the days leading up to landfall.

Although the wind speeds are very similar between the two groups once the storms make landfall, the pre-landfall difference still has an impact on a storm’s destructiveness, says Dr Soheil Radfar, a hurricane-hazard modeller at Princeton University. Radfar, who is the lead author of the new study, tells Carbon Brief:

“Hurricane damage starts days before the landfall…Four or five days before a hurricane making landfall, we expect to have high wind speeds and, because of that high wind speed, we expect to have storm surges that impact coastal communities.”

They also find that rapidly intensifying storms have higher peak rainfall than non-rapidly intensifying storms, with marine heatwave-influenced, rapidly intensifying storms exhibiting the highest average rainfall at landfall.

The charts below show the mean sustained wind speed in knots (top) and the mean rainfall in millimetres per hour (bottom) for the tropical cyclones analysed in the study in the five days leading up to and two days following a storm making landfall.

The four lines show storms that: rapidly intensified with the influence of marine heatwaves (red); those that rapidly intensified without marine heatwaves (purple); those that experienced marine heatwaves, but did not rapidly intensify (orange); and those that neither rapidly intensified nor experienced a marine heatwave (blue).

Dr Daneeja Mawren, an ocean and climate consultant at the Mauritius-based Mascarene Environmental Consulting who was not involved in the study, tells Carbon Brief that the new study “helps clarify how marine heatwaves amplify storm characteristics”, such as stronger winds and heavier rainfall. She notes that this “has not been done on a global scale before”.

However, Mawren adds that other factors not considered in the analysis can “make a huge difference” in the rapid intensification of tropical cyclones, including subsurface marine heatwaves and eddies – circular, spinning ocean currents that can trap warm water.

Dr Jonathan Lin, an atmospheric scientist at Cornell University who was also not involved in the study, tells Carbon Brief that, while the intensification found by the study “makes physical sense”, it is inherently limited by the relatively small number of storms that occur. He adds:

“There’s not that many storms, to tease out the physical mechanisms and observational data. So being able to reproduce this kind of work in a physical model would be really important.”

Economic costs

Storm intensity is not the only factor that determines how destructive a given cyclone can be – the economic damages also depend strongly on the population density and the amount of infrastructure development where a storm hits. The study explains:

“A high storm surge in a sparsely populated area may cause less economic damage than a smaller surge in a densely populated, economically important region.”

To account for the differences in development, the researchers use a type of data called “built-up volume”, from the Global Human Settlement Layer. Built-up volume is a quantity derived from satellite data and other high-resolution imagery that combines measurements of building area and average building height in a given area. This can be used as a proxy for the level of development, the authors explain.

By comparing different cyclones that impacted areas with similar built-up volumes, the researchers can analyse how rapid intensification and marine heatwaves contribute to the overall economic damages of a storm.

They find that, even when controlling for levels of coastal development, storms that pass through a marine heatwave during their rapid intensification cause 93% higher economic damages than storms that do not.

They identify 71 marine heatwave-influenced storms that cause more than $1bn (inflation-adjusted across the dataset) in damages, compared to 45 storms that cause those levels of damage without the influence of marine heatwaves.

This quantification of the cyclones’ economic impact is one of the study’s most “important contributions”, says Mawren.

The authors also note that the continued development in coastal regions may increase the likelihood of tropical cyclone damages over time.

Towards forecasting

The study notes that the increased damages caused by marine heatwave-influenced tropical cyclones, along with the projected increases in marine heatwaves, means such storms “should be given greater consideration” in planning for future climate change.

For Radfar and Moftakhari, the new study emphasises the importance of understanding the interactions between extreme events, such as tropical cyclones and marine heatwaves.

Moftakhari notes that extreme events in the future are expected to become both more intense and more complex. This becomes a problem for climate resilience because “we basically design in the future based on what we’ve observed in the past”, he says. This may lead to underestimating potential hazards, he adds.

Mawren agrees, telling Carbon Brief that, in order to “fully capture the intensification potential”, future forecasts and risk assessments must account for marine heatwaves and other ocean phenomena, such as subsurface heat.

Lin adds that the actions needed to reduce storm damages “take on the order of decades to do right”. He tells Carbon Brief:

“All these [planning] decisions have to come by understanding the future uncertainty and so this research is a step forward in understanding how we can better refine our predictions of what might happen in the future.”

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Marine heatwaves ‘nearly double’ the economic damage caused by tropical cyclones