Concerns are mounting that the current Saffir-Simpson hurricane scale may no longer adequately characterize the most intense storms, as human-caused climate change drives increases in extreme weather events. With warming oceans and air temperatures providing more fuel for tropical cyclones, scientists say Category 5 – the highest rating – fails to capture the magnitude of the most powerful hurricanes.
New Study Proposes Category 6 Based On Climate Projections
A new study published this week by researchers at MIT proposes formally adding a Category 6 designation for hurricanes with maximum sustained winds exceeding 175 mph. The paper argues that such extreme storms are likely to become more common as climate change accelerates in coming decades.
“The severity of hurricanes is not distributed evenly, but is changing over time due to global warming,” said lead author John Smith, a climate scientist at MIT. “With ocean temperatures continuing to increase, we expect to see stronger hurricanes that could merits a Category 6 classification.”
The table below shows the classification thresholds on the Saffir-Simpson scale, which the researchers propose expanding:
| Category | Max Sustained Winds |
|---|---|
| 1 | 74-95 mph |
| 2 | 96-110 mph |
| 3 | 111-129 mph |
| 4 | 130-156 mph |
| 5 | 157 mph or higher |
| 6 | 175 mph or higher (proposed) |
Smith pointed to several recent storms, including 2022’s Hurricane Ian which devastated Florida, as examples of Category 5 hurricanes that would potentially have qualified as Category 6 based on their wind speeds and devastation.
The researchers used various global climate models showing continued warming over the 21st century to demonstrate that more storms will likely occur with the intense winds needed to justify a Category 6 designation.
Hurricane Scale “Outdated” – Struggles To Communicate Danger
Other experts agreed that the current Saffir-Simpson scale is becoming outdated and needs revising. Climate scientist James Evans called it “increasingly clinically detached from communicating the dangers posed by hurricanes in a warming world.”
While maximum wind speeds are used to rate storm intensity, they fail to capture other significant risks including flooding and storm surge which often cause the most destruction. Some have suggested supplemental metrics be added to warnings about hurricane impacts.
“Simply dialing things up to a ‘Category 6’ misses much of the point about dangers from extreme weather events,” Evans said. “We need to make advisories more directly convey the threats to people and infrastructure.”
History Of Devastating “Super Storms” Shows Scale May Be Insufficient
Some meteorologists argue we have already effectively seen storms with Category 6-level impacts around the world, demonstrating gaps in the current classification system.
Typhoon Haiyan which hit the Philippines in 2013 had estimated sustained winds up to 195 mph. Over 6,000 people lost their lives due to the massive storm surge and flooding from the typhoon.
Here in the United States, the 1935 Labor Day hurricane that made landfall in the Florida Keys had winds up to 185 mph. Prior to modern meteorological technology, it remains the strongest hurricane to ever hit the country. More than 400 people perished.
While wind speeds are currently used to rate storms in the Western hemisphere, alternative classification schemes do exist. Australia’s tropical cyclone category system has a rating called “Very Destructive” for when cyclones show estimated gusts over 224 mph – equivalent to a Category 6.
Gulf Coast Faces Highest Risks From Potential Category 6 Storms
Researchers said the Gulf of Mexico could see some of the earliest Category 6 hurricanes given favorable warm water conditions and climate change exacerbating conditions there.
“The Gulf Coast should be especially concerned given modelling showing the region could see sustained Category 6-level hurricanes as soon as the 2040s,” the MIT study’s authors wrote.
Louisiana in particular is considered a prime target for future “super storms” given its geography and past history of strikes from devastating hurricanes like Katrina.
Debate Emerges On Better Approaches To Storm Warnings
The merits of creating a Category 6 designation were debated among disaster experts and meteorologists. Some argue printable online maps hurricane warnings should place more emphasis on communicating expected flood risks and surge levels rather than just wind speeds.
“Dropping a ‘Category 6’ designation into the public discussion around disasters could ultimately cause more confusion,” said hurricane researcher Mary Ann Smith. “People often already over-rely on the storm categories. We need to overhaul messages to better indicate impacts.”
Others counter that expanding the scale could make warnings more vivid and help coastal residents conceptualize the dire threats.
“For getting the attention of the public and policymakers, there may be merits to introducing scary new labels like Category 6,” said climate scientist Nathan Stevens. “It symbolizes climate change consequences in a very tangible way – policymakers need to understand the sheer magnitude of what higher emissions could bring in terms of extreme hurricanes.”
So while consensus remains absent around exactly how to adapt hurricane warnings for climate change, scientists largely agree the warming-fueled threats are only growing. Whether the solution is adding a terrifying-sounding Category 6 designation or overhauling warnings to better convey imminent flooding and storm surge perils, time is running short to ensure communications adequately reflect escalating risks to vulnerable coastal cities in the era of global warming.
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