Marine heat waves ‘almost double’ the economic damage caused by tropical cyclones

Tropical cyclones that rapidly intensify as they pass over sea heat waves can become “overloaded,” increasing the likelihood of large economic losses, a new study has found.

Such storms also have higher rainfall rates and higher maximum wind speeds, according to the study.

A study published in Achievements of scienceexamines the economic damage caused by nearly 800 tropical cyclones that occurred worldwide between 1981 and 2023.

He found that even after accounting for coastal development, rapidly intensifying tropical cyclones that pass near abnormally warm parts of the ocean cause nearly twice as much economic damage as storms that do not, with 93% more losses.

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.

Because marine heat waves are projected to become more frequent with future climate change, the authors say the interaction between storms and these heat waves “should be given more attention in future climate adaptation and climate preparedness strategies.”

“Rapid Intensification”

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

The term “tropical cyclones” covers hurricanes, cyclones and typhoons, which are named after the ocean basin in which they occur.

When they make landfall, these storms can cause a lot of damage. They took into account six of the top 10 catastrophes between 1900 and 2024 in terms of economic losses, according to information on climate catastrophes from the insurance company Aon 2025 the report.

These economic losses are largely caused by high wind speeds, heavy rainfall and damage storm surges.

A storm can become particularly dangerous through a process called “rapid intensification“.

Rapid intensification is when a storm strengthens significantly in a short period of time. It is defined as an increase in sustained wind speed of at least 30 knots (about 55 kilometers per hour) within 24 hours.

There are several factors that could lead to rapid intensification, including high ocean temperatures, high humidity, and low vertical.”wind shear” – this means that the wind speed higher in the atmosphere is very similar to the wind speed near the surface.

Rapid intensification became more common since the 1980s and is projected to continue even more often in the future while maintaining warming. (Although there is uncertainty on how climate change will affect the frequency of tropical cyclones increasing strength and intensification more clear.)

Sea heat are another type of extreme events that become more often due to recent warming. Like their atmospheric counterparts, marine heat waves are periods of abnormally high ocean temperatures.

Previous studies have shown that these marine heat waves can contribute to the rapid intensification of the cyclone. That’s because warm ocean water acts as “fuel” for the storm, he says Dr. Hamed MoftahariAssociate Professor of the Department of Civil Engineering in University of Alabama who was one of the authors of the new study. He explains:

“All the strength of a tropical cyclone (depends on how hot the (ocean) surface is). A marine heat wave means we have a lot of hot water, like a gas station. When you move through that, you’re going to be overwhelmed.”

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

Using International archive of the best tracks on climate management (IBTrACS) – Tropical Cyclone Tracks and Intensity Database – researchers identify 1,600 storms that made landfall between 1981 and 2023, out of a total of 3,464 events.

Of these 1,600 storms, they were able to match 789 individual landfalling cyclones with economic loss data from Database of emergency incidents (EM-DAT) and other official sources.

Then, using IBTrACS storm data and ocean temperature data from European Center for Medium-Range Weather Forecastsresearchers classify each cyclone by whether it underwent rapid intensification and whether it passed near recent sea heat before making landfall.

The researchers find that there has been a “modest” increase in the number of heat-driven marine tropical cyclones worldwide since 1981, but with significant regional variation. In particular, they say, there are “clear” upward trends in the North Atlantic Ocean, the North Indian Ocean and the Northern Hemisphere basin in the East Pacific.

“Storm Characteristics”

The researchers find significant differences in the characteristics of tropical cyclones that experience rapid intensification and those that do not, and between rapidly intensifying storms that occur with marine heat waves and those that do not.

For example, non-rapidly intensifying tropical cyclones have an average maximum wind speed of about 40 knots (74 km/h), while rapidly intensifying storms have an average maximum wind speed of about 80 knots (148 km/h).

Of the rapidly intensifying storms, those affected by the sea heat maintain higher wind speeds for several days before making landfall.

Although the wind speeds between the two groups are very similar when the storm makes landfall, the difference before landfall still affects the destructiveness of the storm, says Dr. Sohail Radfarhurricane hazard modeler in Princeton University. Radfar, who is the lead author of the new study, tells Carbon Brief:

“Hurricane damage starts a few days before landfall…Four to five days before a hurricane makes landfall, we expect wind speeds to be high, and because of those high wind speeds, we expect storm surges which affect coastal communities’.

They also found that rapidly intensifying storms have higher peak precipitation than non-rapidly intensifying storms, with rapidly intensifying storms driven by sea heat showing the highest average rainfall at landfall.

The charts below show the average sustained wind speed in knots (top) and the average rainfall in millimeters per hour (bottom) for the tropical cyclones analyzed in the study, five days before and two days after the storm made landfall.

The four lines show storms that: rapidly intensify under the influence of sea heat (red); those that intensified rapidly without sea heat (purple); those that survived the marine heat but did not intensify rapidly (orange); and those that did not intensify rapidly and were not exposed to marine heat (blue).

Dr. Danija Morenocean and climate consultant in Mauritius Environmental consulting Mascarene who was not involved in the research, tells Carbon Brief that the new study “helps to clarify how marine heat waves amplify storm characteristics” such as strong winds and heavy rainfall. She notes that this “has never been done before on a global scale.”

However, Moren adds that other factors not accounted for in the analysis can “make a huge difference” in the rapid intensification of tropical cyclones, including subsurface marine heat waves and eddies – circular, rotating ocean currents that can trap warm water.

Dr. Jonathan Lynnatmospheric 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 essentially limited to the relatively small number of storms that occur. He adds:

“There are not so many storms to study the physical mechanisms and observational data. Therefore, the opportunity to reproduce such work in physical model would be very important.”

Economic costs

The intensity of a storm is not the only factor that determines how destructive a given cyclone can be – economic losses are also highly dependent on population density and the degree of infrastructure development in the storm’s location. The study explains:

“A severe 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 developmental differences, researchers use a type of data called “accumulated volume,” with Global layer of settlements. Built-up area is a quantity derived from satellite data and other high-resolution imagery that combines measurements of built-up area and average building height in a given area. This can be used as a proxy for developmental level, the authors explain.

By comparing different cyclones that hit areas with similar built-up areas, researchers can analyze how rapidly increasing sea heat contributes to the overall economic damage from the storm.

They found that, even when controlling for the level of coastal development, storms that pass through a marine heat wave during their rapid intensification cause 93% more economic damage than storms that do not.

They identify 71 storms caused by sea heat that caused more than $1 billion in damage (adjusted for data set inflation), compared to 45 storms that cause that level of damage without the effect of sea heat.

This quantification of the economic impact of cyclones is one of the most “important contributions” to the study, Moren says.

The authors also note that further development in coastal regions could increase the likelihood of damage from tropical cyclones over time.

Before forecasting

The study notes that the increase in damage caused by marine tropical cyclones, as well as the projected increase in marine heat waves, means that such storms “should receive more attention” when planning for future climate change.

For Radfar and Moftahari, the new study highlights the importance of understanding the interactions between extreme events such as tropical cyclones and marine heat waves.

Maftahari notes that extreme events are expected to become more intense and more complex in the future. This becomes a challenge for climate resilience because “we’re basically projecting the future based on what we’ve seen in the past,” he says. This could lead to an underestimation of potential dangers, he adds.

Moren agrees, telling Carbon Brief that in order to “fully exploit the potential for intensification,” future projections and risk assessments must take into account marine heat waves and other ocean phenomena such as geothermal heat.

Lynn adds that the actions needed to mitigate the damage from the storm “will take decades to get right.” He tells Carbon Brief:

“All of these (planning) decisions have to be made with an understanding of the uncertainty of the future, and so this study is a step forward in understanding how we can better refine our predictions of what might happen in the future.”