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OPINION

Is this the beginning of the Category 6 hurricane?

Category 5 is what we use to identify the strongest hurricanes on the planet, with sustained winds of 157 miles per hour or more. But some Atlantic hurricanes are arguably strong enough to merit a Category 6 designation thanks to climate change.

An aerial view of Lafitte, La., after Hurricane Ida, one of the strongest storms in the state's history, made landfall in September.
An aerial view of Lafitte, La., after Hurricane Ida, one of the strongest storms in the state's history, made landfall in September.JOHNNY MILANO/NYT

Imagine a world where Category 6 hurricanes threaten the East Coast, with sustained winds of 200 mph and storm surges in the 30-foot range. The devastation would be almost unimaginable — all the glass blown out of high-rise buildings, homes wiped off their foundations, and neighborhoods well inland completely underwater from the storm surge.

In some ways, we don’t have to imagine it — we are already living in a new era of superstorms. Category 5 is what we use to identify the strongest hurricanes on the planet, with sustained winds of 157 miles per hour or more. But some Atlantic hurricanes, such as Dorian in 2019, have had sustained winds in the 185 miles-per-hour range. That’s arguably strong enough to merit a Category 6 designation.

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Thanks to human-caused climate change, we are hurtling toward a world where such Category 6 storms may become a familiarity. Estimates are that the maximum wind speeds of Atlantic hurricanes increase about 17 miles per hour per degree Celsius. That’s enough to shift storms a whole category given 1 degree Celsius (approximately 2 degrees Fahrenheit) of warming, which is what we’ve already seen over the past century.

The calls for adding this next category of storms are growing louder. And I’ve added my voice to them. My own scientific work adds to a growing body of research suggesting that climate change is exacerbating the coastal threat from these storms.

If the concept of a Category 6 storm isn’t scary enough, there may be an even worse future in store if we fail to act on the climate crisis. Picture an EF-5 tornado hundreds of miles wide scouring the landscape. That would be the same as a theoretical Category 7 hurricane packing 220-plus miles-per-hour sustained winds and a 40-foot storm surge that could swamp a coastal metropolis and leave a region uninhabitable for years. The human toll would be unbearable.

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While this might sound like the stuff of a sci-fi film, it could one day become our reality — if we continue to elevate the concentration of carbon pollution in the atmosphere through the burning of fossil fuels and warm the planet another 1 degree Celsius.

We’re living in a new world where rapid intensification and major hurricanes are becoming more and more frequent. The parade of deadly and destructive hurricanes over the past two decades are etched in our memories: Ivan, Katrina, Rita, Wilma, Matthew, and Michael, among others. Each was a Category 5 storm, packing winds of 160 miles per hour or more with storm surges in excess of 15 feet. Such devastating storms were once extremely rare. Today, they are considerably more common. If we continue to warm the planet, they’ll get worse still.

Burning fossil fuels — such as coal, oil, and natural gas —not only warms the surface of the planet, but the ocean is getting warmer as well. The heat content of the upper ocean, which has reached record levels in recent years, is like a huge, fully-charged battery that supercharges hurricanes — stronger wind, higher storm surge. Take Ida for example: As it went over an unusually deep layer of warm water in the Gulf of Mexico, it was able to rapidly intensify from a Category 1 to a near-Category 5 hurricane in just a day, shortly before it made landfall in Louisiana. A degree or two warmer and it might well have fit the Category 6 definition.

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But it isn’t just the wind and surf that threaten human life and livelihood. There’s the additional flooding rain. It’s not a coincidence that the two worst flooding events in US history were associated with two recent landfalling hurricanes — Harvey and Florence. Warmer oceans evaporate more moisture into the atmosphere, and stronger storms entrain more moisture into them. It’s a double whammy that gives us unprecedented flooding events.

That might sound a bit theoretical, but let me give you a real-world example: Ida. This historic storm drenched not only the Gulf Coast where it made landfall, but also well inland days later as it produced catastrophic flooding in the Northeast United States: 3.15 inches fell in Central Park in New York in just 60 minutes.

In Eastern Massachusetts, Ida brought a tornado to Cape Cod and more than 9 inches of rain in New Bedford. And if you’re looking for one more piece of bad news, a growing body of research, including my own, suggests that climate change is increasing the odds of monster storms drifting farther north and striking New England.

We must as a society decide if we want to continue down the path we’re on, where climate change loads the dice in favor of withering heat waves, explosive wildfires, devastating flooding, and major hurricanes. Or do we want to decide to make the changes necessary to mitigate climate change, namely by ending the use of fossil fuels and slowing down the runaway train of global warming? The choice is ours to make.

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Michael E. Mann is distinguished professor of atmospheric science and director of the Earth System Science Center at Penn State University. He is author most recently of “The New Climate War: The Fight to Take Back our Planet.”