First the deadly Helene, now Milton: Climate change is changing hurricane dynamics

Earlier this week, Hurricane Milton intensified in the Gulf of Mexico, swiftly reaching Category 5 status, the highest level on the Saffir-Simpson scale. After leaving a path of destruction across the Yucatán Peninsula in Mexico, there is no doubt that it is an extreme event capable of causing devastating damage in Florida, which has yet to recover from the previous hurricane.

Hurricane Milton poses an “extremely serious risk” to Florida, according to the National Hurricane Center (NHC). “If you stay, you are going to die,” warned Tampa Mayor Jane Castor, urging residents to evacuate their homes as the hurricane is expected to have its greatest impact on the city.

This is not the first time residents in Florida have heard such warnings in the past two weeks. On September 26, Hurricane Helene made landfall in Florida as a Category 4 storm, moving inland and bringing torrential rains to Georgia, the western Carolinas, eastern Tennessee, and southern Virginia. The devastating impact resulted in 227 deaths, making it the second-deadliest hurricane in U.S. history, surpassed only by Katrina in 2005. Additionally, two million people were left without electricity, and damage from Helene has yet to be repaired as Milton approaches.

“This was such a massive event that it flooded almost everything in its path all the way to Ohio, not just the coast,” said Bernadette Woods Placky, chief meteorologist at Climate Central in the United States, during a press conference for World Weather Attribution (WWA), an organization of scientists that seeks to address what role climate change plays in an extreme event like Hurricane Helene.

Scientists have long warned that climate change driven by human activities is making hurricanes more destructive. However, a new study by WWA — though not yet peer-reviewed — utilizes established methodologies to examine how this relationship has manifested in the case of Hurricane Helene. According to the research, climate change has increased the likelihood of such intense hurricanes occurring in the region by 2.5 times compared to the pre-industrial era. In other words, a hurricane of this magnitude, which was once expected to happen once every 130 years, is now projected to occur once every 53 years.

Understanding how hurricane dynamics shift with global warming involves putting several pieces together. To this end, Ben Clarke, a researcher at the Grantham Institute at Imperial College London, and his team analyzed indices and models related to three key factors: rainfall patterns, wind, and ocean surface temperatures —the latter being crucial for fueling hurricanes. They examined data from the coastal region, where intense rainfall lasted for two days, as well as the continental areas, which experienced heavy rainfall for up to three days.

“In both regions, the rainfall was about 10% heavier due to climate change,” the study says, clarifying that it was 40% heavier on the coast, where it rained for two days, and 70% more intense on the mainland, which saw three days of rain. “If the world continues to burn fossil fuels, causing global warming to reach 2°C above pre-industrial levels, devastating rainfall events in both regions will become another 15-25 % more likely.”

The study also found that climate change increased Hurricane Helene’s winds by 11%. Additionally, rising ocean surface temperatures in the Gulf of Mexico — just above average at the time Helene passed through — were 200 to 500 times more likely due to climate change. Compounding this climatic mix was Helene’s unusual trajectory, which took it further offshore toward Ohio, a region lacking the hurricane preparedness of Florida.

“Most of the deaths occurred farther inland, in the mountainous terrain where challenges such as spotty cell and internet services, limited experience with Hurricanes and more limited evacuation infrastructure have been reported in the media as leaving people feeling caught off guard,” the study said.

Yes, climate change is transforming hurricane dynamics. It’s not just about Helene; it’s also about Milton and the storms to come. An analysis by Climate Central found that the high ocean temperatures fueling Milton have become 400 to 800 times more likely due to climate change.

As he watched images of Hurricane Milton’s progress and described its path on live television, Puerto Rican meteorologist John Morales’ voice cracked. “I apologize. This is just horrific,” he said, fully aware of the gravity of the situation unfolding before him. He recognizes the increasing unpredictability of weather patterns. After years of studying these phenomena, he senses that hurricane seasons in the Atlantic will become progressively more challenging.

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