Climate scientists are proposing adding a new Category 6 designation to the Saffir-Simpson Hurricane Wind Scale as hurricanes are projected to intensify further with climate change.
Current Scale Only Goes Up To Category 5
The Saffir-Simpson scale currently categorizes storms on a 1 to 5 scale based solely on maximum sustained wind speeds, with 5 being the highest category defined. As explained by The Guardian:
The scale rates hurricanes from one to five based only on their wind speed, with five being the strongest, over 157mph. But over the past decade storms have brought impacts that the scale does not capture, such as extreme rainfall and storm surge flooding.
However, recent hurricanes have brought devastating impacts beyond just wind speeds. According to USA Today:
In the past decade, hurricanes with wind speeds that qualify as Category 5 – such as Michael in 2018, Irma and Maria in 2017 and Ida in 2021 – have brought wind damage along with devastating and deadly storm surge and extreme rainfall that overwhelm infrastructure and kill people.
This indicates the scale may not be adequately capturing the full destructive potential of hurricanes in the modern climate.
Hurricanes Getting Stronger With Warming
Scientists warn hurricanes are likely to continue getting stronger as the world warms. Rising ocean temperatures provide more fuel for storms, while higher sea levels exacerbate dangerous storm surge flooding.
According to climate scientist Michael Mann in Salon:
“Climate change is making hurricanes more destructive. Not only are we seeing them intensify at a remarkable rate, they are moving more slowly once they make landfall, which can worsen the impacts of their wind, storm surge and rainfall.”
The proportion of storms reaching Category 4 or 5 levels is already projected to increase with additional warming. Adding a Category 6 designation could help better communicate this risk.
Reasons For Category 6 Proposal
There are several key reasons scientists argue for defining an additional Category 6 designation beyond the current 5 category scale:
Better communicate intensification risk: Having a Category 6 would more clearly signal the significant projected strengthening of storms.
Capture total impact: The scale currently only accounts for wind speeds. A new category could help account for other devastating impacts like extreme rainfall and flooding.
Motivate action: Clearly highlighting the risk for unprecedented extreme hurricane events could help motivate emission reductions and climate adaptation efforts.
However, some scientists argue against adding a new category, suggesting continuing rising damage is more a factor of increasing coastal development than climate impacts.
What Wind Speed Would Qualify As Category 6?
There is no set consensus yet on what wind speed would qualify a storm as Category 6, but estimates range from around 175-200 mph.
As explained by Mann:
“Scientistically, I could certainly see merit in formalizing a Category 6 designation for storms with sustained winds exceeding 175 or 180 miles per hour.”
For context, among the strongest storms on record, 2022’s Hurricane Fiona reached peak sustained winds around 165 mph.
|Peak Wind Speed
Allen, Patricia and Dorian would likely have qualified for a Category 6 designation if it existed, with winds well exceeding 175 mph.
Locations Most At Risk
Some locations most vulnerable to these intensifying Category 6 hurricanes include:
Florida: With a dense coastal population and already battered by storms like Ian, Florida is at major risk of impacts. Miami in particular is considered the most vulnerable major coastal city globally.
Gulf Coast: Major oil infrastructure and important shipping ports line the Gulf Coast, along with cities like New Orleans vulnerable to extreme flooding.
Hawaii: Remote island geography makes disaster response extremely challenging.
Caribbean Islands: Poor infrastructure and high poverty levels reduce resilience on islands like Puerto Rico and limit the ability to prepare and recover.
Calls For Action
Many experts argue new risk information like the Category 6 proposal helps highlight the urgent need for action on emissions reductions and climate adaptation.
As Mann summarizes:
“It’s time for us to start preparing for even more severe tropical cyclones by updating building codes, improving early warning systems, building higher seawalls, developing technologies for rapid disaster response and recovery, and so on. And it’s time for us to reduce carbon emissions to minimize the threat.”
In particular, adapting infrastructure design and building codes to account for more extreme flooding and winds could significantly improve resilience.
The scale proposal also further builds the case for strong policies to rapidly cut greenhouse gas emissions and limit additional warming. Every fraction of a degree increase matters in controlling hurricane intensities.
Without serious adaptation efforts and emission cuts, damage from extreme storms threatens to rise to unprecedented levels. But taking action now can substantially reduce these mounting risks to coastal communities.
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