| By Lauren Rosenthal and Mary Hui Climate change is cranking up the intensity of tropical cyclones. Known as hurricanes or typhoons depending on where they’re spawned, these spinning storms are becoming more potent as warmer seas and a hotter atmosphere provide more fuel. Ocean temperatures have been breaking heat records, in some places approaching the feel of a comfortable bath, and ramped-up evaporation rates are loading cyclones with trillions of gallons of rainfall. At the same time, wind shear that can help keep storms in check has been weakening in some parts of the world as sea temperatures rise. While there’s no clear evidence that climate change is increasing the frequency of tropical cyclones, the damage inflicted by more powerful storms will likely reach further inland. This has already endangered communities that aren’t used to the extreme weather that these storms bring, including flash floods and violent, tree-toppling winds that can demolish infrastructure and leave people without access to power or clean water for weeks. Here’s how climate change is transforming hurricanes and typhoons from the inside out. Tropical cyclones feed off heat and waterA key ingredient for cyclones is warm water, which releases heat and creates humid air as it evaporates from the sea surface. The moisture is absorbed into the burgeoning storm and cools to form clouds and thunderstorms. Ocean water needs to be at least 80F (27C) at the surface and warm to a depth of about 150 feet — around 46 meters, or nearly half the length of a soccer field — to provide sufficient fuel for a cyclone. Other crucial inputs include the rotational effect of the planet, which gives tropical cyclones their spin, and the absence of strong crosswinds outside the storm, which can disrupt its growth. Climate change is turning up the heatIn the Atlantic, developing storms tend to gather momentum as they stream westward over the ocean from the African coast. Along the way, they often cross a belt of extra-warm water known as the “Main Development Region.” A jolt of energy and moisture from these waters can help a storm coalesce into a fully fledged tropical cyclone. In recent years, the amount of thermal energy stored in this part of the ocean and surrounding areas has surged as the Atlantic heats to record-high temperatures — approaching 90F in some spots. Research suggests the main culprit driving that warming is human-caused climate change linked to increased greenhouse gas emissions. Other factors include reduced aerosol pollution. In recent years, theories that suggested warming was also connected to natural fluctuations have fallen out of favor with some scientists. Historically, the ocean cools down somewhat after a massive hurricane or typhoon sweeps across it, which helps lower the amount of energy available for the next storm system passing through. But in the Atlantic, that cooling pattern is becoming shorter-lived, fueling devastating back-to-back hurricanes such as Helene and Milton, which ripped through Florida less than two weeks apart in fall 2024. Disruptions that slow cyclones’ intensity are weakeningWarmer temperatures at the sea surface tend to weaken the crosswinds that can interfere with the growth of tropical storms. When strong winds run vertically up the sides of a growing storm system, for instance, they can shred the structure of the brewing hurricane or typhoon before it fully forms. As the oceans heat up, researchers have observed fewer opportunities for strong, storm-killing winds to develop. A recent study suggested these winds will decline close to land as climate change intensifies. Storms are getting stronger, fasterTropical cyclones aren’t becoming more frequent, but they are getting more powerful and intensifying more quickly, reaching higher maximum wind speeds. Storms in the Atlantic Ocean are also taking less time to reach their top speeds once they form. Hurricanes are now more likely to undergo a process called “rapid intensification,” whereby their winds pick up by at least 35 mph in the span of 24 hours. Researchers have also found that the proportion of hurricanes classified as “major” — meaning they’re at least a Category 3 storm — has already increased by about 5% per decade since 1979. They’re also getting wetterMore of these storms are forming earlier in the season compared to several decades ago. Earlier appearances are pushing tropical cyclones closer to peak rainy season, compounding the impact of extreme precipitation produced by other weather systems and from hurricanes and typhoons. Tropical storms are also getting wetter overall. That’s partly because warmer air is capable of pulling more moisture from the surrounding environment, including the ocean’s surface, leading to heavier rains once storms make landfall. One widely cited study found that the average rainfall rate of tropical cyclones increased by 1.3% per year over the course of 1998 to 2016, driven by warmer sea surface temperatures and a more moist environment. That’s given rise to deadly, rain-packed storms such as Hurricane Harvey, which dropped as much as 56 inches (1.42 meters) of precipitation as it stalled over Houston, Texas, in 2017. Read the full story. | 
