Climate change isn’t the sole cause of any hurricane, but it might affect them

Hurricane Ian was still churning toward Florida on Sept. 27 when CNN anchor Don Lemon asked one of the nation’s leading meteorologists a question about climate change.

"Can you tell us what this is and what effect climate change has on this phenomenon?" Lemon asked as National Hurricane Center Acting Director Jamie Rohme stood before a screen showing the swirling graphics of the Category 4 storm overtaking the Gulf of Mexico.

"We can come back and talk about climate change at a later time," Rhome responded. "I want to focus on the here and now." Then he turned back to his screen to show what he described as a second eye wall forming around the inner eye wall.

Lemon appeared unsatisfied: "You said you want to talk about climate change, but what effect does climate change have on this phenomenon that is happening now," he asked again. "Because it seems these storms are intensifying."

"I don’t think you can link climate change to any one event," Rhome answered. "On the cumulative, climate change may be making storms worse, but to link it to any one event, I would caution against that."

Lemon, who is from Louisiana, pushed back: "Listen, I grew up there. These storms are intensifying. Something is causing them to intensify."

The exchange caused a bit of a stir with critics, who suggested Lemon was pushing a climate change agenda. Twitter users and news outlets alike joined in. 

But it seems to illustrate a commonly asked question — one that takes longer to explain than Lemon or Rohme were given.

So PolitiFact took that question (and many others) to experts.

Hurricanes form when humid air over warm ocean waters flows upward, creating clouds from the water the air releases, according to the University Corporation for Atmospheric Research. The air rotates as it rises, and it grows as warm ocean water and warm, moist air feeds it.

The more warm air, and the more warm ocean waters, the stronger the hurricane.  

Hurricanes happened before the climate crisis. And climatologists say the extent to which climate change is affecting them is hard to nail down in a concise talking point. 

"The problem is akin to having a grandparent who dies of lung cancer and who had smoked two packs a day," Kerry Emanuel, a climate scientist with a specialty in hurricane physics at MIT, wrote in an email. "You can say that his smoking made his cancer more likely, but some people who never smoked still get lung cancer, and some who smoked heavily lived until well into their 90s.

"Climate change has made intense, highly precipitating storms like Ian more likely."

Still, the science is complicated, as Phil Klotzbach, senior research scientist at the Department of Atmospheric Science at Colorado State University described.

"The relationship between hurricanes and climate change is a topic of vigorous scientific debate," Klotzbach wrote in an email. "If you were to email some of my colleagues, they may give you a somewhat different take than what I am going to give you, which highlights the uncertainty that we still have about the relationship."

A consensus paper published in the Bulletin of the American Meteorological Society in 2019 yielded no clear "yes" or "no" answer about how much human-caused climate change affects hurricane frequency and intensity.

Klotzbach also said climate change is raising sea levels and increasing the air’s ability to hold moisture, which means storm surges penetrate further inland and produce more rain. But then, warm temperatures can stabilize the atmosphere and reduce a hurricane’s intensity, and there are many other factors that are still being studied.

NOAA has published a page of resources and discussions on the potential links between climate change and hurricanes. A representative from NOAA also pointed out that "The acting NHC director clearly stated that ‘on the whole, on the cumulative, climate change may be making storms worse.’ That is supported by the overwhelmingly clear science on what climate change means for storms like Ian in general…" in an e-mail to Time.

Yes and no.

Global hurricane counts and accumulated cyclone energy have significantly decreased since 1990, according to a 2022 paper in the journal Geophysical Research Letters. But short-lived named storms and extreme rapid intensification events have increased. 

Hurricane damage has increased, too, the 2022 paper stated. Part of the reason, Klotzbach said, is that there are "more people and property in harm's way," noting that the population in Fort Myers, in southwest Florida, has increased considerably over the years. 

Mark Bourassa, a professor of meteorology at the Department of Earth, Ocean and Atmospheric Science at Florida State University’s Center for Oceanic-Atmospheric Prediction Studies, supports Rohme’s statement. 

He wrote in an email: "The statement from NOAA is correct that it is statistically impossible for hurricane researchers to attribute any single event to climate change. There is too much variability in hurricane strength that we don't understand. That variability likely overwhelms the climate change signal." 

In short, hurricanes happen for a variety of reasons, with or without human-caused climate change. No hurricane will ever be caused exclusively by one thing, but many elements come together — hence the phrase "perfect storm."

Many of those elements are affected by climate change, and may make storms of certain types and intensities more common, but the science is still complex and evolving.