Hurricane Helene’s Deadly Rainfall and Wind Increased by Human-Made Climate Change, Study Reveals

Hurricane Helene, one of the costliest and deadliest hurricanes to hit the US, left at least 227 dead across six states.

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A devastating hurricane that killed more than 200 people across six US states was made more intense and likely to occur by human-made climate change, a new study has revealed.

Category 4 Hurricane Helene slammed into Florida on September 26, packing winds of up to 140 mph (225 km/h) and driving a record-breaking storm surge up to 15ft (4.5m). It then moved inland, from Georgia all the way to Virginia passing through South Carolina, North Carolina and Tennessee, where it dumped huge amounts of rain.

By analyzing weather data and climate models to compare how similar events have changed between today’s climate – which has warmed approximately 1.3C – and the cooler pre-industrial climate, a team of leading scientists found that climate change made Helene’s winds some 11% more intense and its rains 10% heavier.

Along its 600-mile (965-kilometer) path, Helene killed at least 227 people, the second-highest number after Hurricane Katrina in 2005.

Helene strengthened from a Category 2 to a Category 4 hurricane in just ten hours, a phenomenon that is happening more and more often with climate change. Rapidly intensifying storms leave less time for authorities to issue warning systems, putting coastal communities in great danger. In 2022, for example, Hurricane Ian devastated portions of Florida after it rapidly intensified, packing two days’ worth of rapid intensification into less than 36 hours.

Helene’s rapid intensification, like most recent hurricanes, was fuelled by ultra-warm ocean temperatures in the Gulf of Mexico, which are currently about 3.6F (2C) above average. The likelihood of such high sea temperatures, the study revealed, was 200-500 times higher because of climate change.

As ocean surfaces warm, so does the air above it, causing water to be carried up to high altitudes to form clouds, while leaving a low pressure zone beneath causing more air to rush in. The warmer the air, the more water it can “hold,” and the amount of moisture in the atmosphere is expected to increase by up to 7% per degree of warming. 

As these systems build up, thunderstorms are formed, and if there are no strong winds to slow it down, they can become hurricanes. While the number of hurricanes is not necessarily increasing, those that do form are becoming more destructive – generating heavier rain and a higher storm surge.

The study, published Tuesday by World Weather Attribution (WWA), is just the latest confirmation of what scientists have been saying for years: climate change, primarily caused by the burning of fossil fuels and deforestation, is making extreme weather events such as tropical cyclones more destructive.

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“If humans keep heating the climate, we will keep seeing storms rapidly morph into monster hurricanes, leading to more destruction,” said Bernadette Woods Placky, Chief Meteorologist at Climate Central and one of the scientists behind the study.

The authors warned every US state to prepare for climate change, as downpours unleashed by hurricanes intensify.

“Helene is a tragic reminder that it is not just coastal areas that are vulnerable to the impacts of
tropical cyclones and hurricanes – wetter and stronger storms pose a growing threat far inland,” said Gabriel Vecchi, Knox Taylor Professor of Geosciences and Director of the High Meadows Environmental Institute at Princeton University.

“It is essential that society not only work to adapt, but also recognize that future warming and climate
impacts will depend upon decisions and actions we make now and in the coming years. It’s up to us:
if we meaningfully reduce greenhouse gas emissions, we will make the challenge to future
generations more manageable.”