February 27, 2024

Scientists Propose New “Category 6” for Hurricanes as Storms Strengthen with Climate Change

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Feb 6, 2024


With climate change causing hurricanes to intensify faster and become more destructive, scientists are proposing adding a new “Category 6” designation to the Saffir-Simpson Hurricane Wind Scale, which currently only goes up to Category 5. [1] [2] Recent studies have shown that hurricanes are intensifying more rapidly, dropping more rainfall, and have higher storm surges due to warming oceans and air temperatures. [3] With Category 5 storms like Hurricane Dorian in 2019 already causing catastrophic damage, scientists say an expanded scale is needed to communicate the true risks of supercharged storms in a changing climate. [4]

Lead Up

The Saffir-Simpson Hurricane Wind Scale was introduced in the early 1970s to provide measurements of hurricane intensity based solely on maximum sustained wind speeds. [5] It categorizes storms from Category 1 with winds 74-95 mph up to Category 5 with winds over 157 mph. For decades, this 1-5 scale has been the standard for hurricane forecasting and public communications.

Saffir-Simpson Hurricane Scale

Saffir-Simpson Hurricane Wind Scale. Source: Wikimedia Commons

However, recent research has shown the scale does not capture the full impacts of hurricanes in a warming world. Due to rising global temperatures, storms are intensifying more rapidly over warmer oceans, supercharging their winds and rainfall. [6] They are also moving more slowly after landfall, dumping higher volumes of rain that causes catastrophic flooding. [7] And their storm surges are worsening due to sea level rise, sending walls of ocean water surging far inland. [8]

While Category 5 storms used to be rare, we have seen more in recent years including Hurricanes Dorian, Lorenzo, Irma, Maria, and Michael. The catastrophic damage they caused with winds over 157 mph spurred scientists to investigate whether the scale needs updating for the era of climate change.

Current Developments

In a new study published this week in the Bulletin of the American Meteorological Society, MIT climate scientist Kerry Emanuel proposes expanding the hurricane scale to include a new Category 6 designation for storms with winds over 175 mph. [9] Based on climate models, he says we could start seeing these extremely high-wind storms by the end of the century, causing damage we cannot yet imagine from winds, rainfall, and storm surge.

“In a world that warms by around 3-4 degrees Celsius by 2100, the power of Category 6 storms, with sustained winds over 175 mph, would be mostly unprecedented,” Emanuel explains. [10]

Emanuel says adding an additional Category 6 designation could better communicate to the public, media, and officials the true risks we face from supercharged hurricanes in our changing climate:

“Expanding the scale introduces the unfamiliar and perhaps unwanted concept of still more dangerous storms while failing at informing about this primary attribute of societal importance—the risk,” he argues. [11]

Hurricane Destruction

Hurricane damage in the Bahamas. Source: Shutterstock

His proposal for a Category 6 builds on previous studies arguing the current scale fails to capture key hurricane hazards that cause loss of life and damage: extreme rainfall, storm surge and flooding. Some have called for an expanded scale that rates hurricanes across multiple impact factors including wind, surge, and rainfall. [12]

Emanuel says simply adding a Category 6 designation could be a pragmatic way to update the familiar wind scale until more comprehensive rating systems are developed. It sends a clear message that climate change is amplifying these storms beyond what we have experienced before.

What Could Happen Next

Emanuel’s proposed Category 6 designation is already spurring debate in the meteorological community about how to update the Saffir-Simpson scale for climate change. While wind speed indicates intensity, some argue other metrics like air pressure, rainfall rates, size of storm are better indicators of total devastation. [13] Some news outlets have called for ratings of these additional factors to be incorporated alongside wind categories, with visual guides similar to the hurricane cones used in forecasts. [14]

There is also discussion around better incorporating ongoing exposure and vulnerability risks into warnings and forecasts. Simply expecting communities to evacuate based on wind speed fails to consider realities like homelessness, poverty, disabilities that make it much harder for people to seek safety. [15] Adjusting warnings and protective measures based on degrees of social vulnerability could help mitigate the disaster disparities climate change is worsening.

Degree of Social Vulnerability Potential Loss of Life Damage Risk Protective Action Needed
Very High Extremely High Catastrophic, long-term Mandatory evacuation orders
High Very High Extensive, years Transportation assistance, temporary housing planned
Moderate Moderate Widespread, months Community shelters readied
Low Low Localized, weeks Prepare emergency kits

Proposed hurricane warning system incorporating social vulnerability risks

While expanding storm categories will take time, there are calls for National Hurricane Center and NOAA to immediately begin incorporating climate change effects into forecasts to reflect our new reality of faster-strengthening storms. [16] Better predictive capabilities would allow more advance warning that storms will undergo rapid intensification so coastal residents have more time to evacuate. Next generation forecast models and supercomputing investments could enable these life-saving improvements.

The Bottom Line

The fact that scientists are now proposing something as dramatic as a Category 6 hurricane is a warning sign of how climate change is creating weather unprecedented in human history. [17] While expanding warning systems will take time and investment, this new evidence underscores the critical importance of driving global carbon emissions down rapidly if we want to limit supercharged storms ravaging our coastlines. Our collective future depends on heeding scientists’ calls for radical climate action before Category 6 monster hurricanes become a norm.




AiBot scans breaking news and distills multiple news articles into a concise, easy-to-understand summary which reads just like a news story, saving users time while keeping them well-informed.

To err is human, but AI does it too. Whilst factual data is used in the production of these articles, the content is written entirely by AI. Double check any facts you intend to rely on with another source.

By AiBot

AiBot scans breaking news and distills multiple news articles into a concise, easy-to-understand summary which reads just like a news story, saving users time while keeping them well-informed.

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