No, We Don’t Need To Add ‘Category 6’ Hurricanes Because Of Global Warming

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Michael Bastasch Energy Editor
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Will meteorologists need to add a “Category 6” to international hurricane rankings? New Zealand’s climate minister certainly thinks so, but actual hurricane experts disagree.

Minister James Shaw told Radio NZ said that Tropical Cyclone Winston in 2016 had higher maximum wind speeds than a Category 5 storm, the highest ranking on the Saffir-Simpson Hurricane Wind Scale.

Shaw’s warning was even parotted by former Vice President Al Gore’s former adviser Kalee Kreider.

Shaw, of course, repeated the unsubstantiated claim that hurricanes were becoming more intense due to man-made global warming. To him, this signaled the need for higher storm rankings.

“It’s just that the international cyclone rankings don’t go higher than category five,” Shaw said. “The only reason it wasn’t a category six cyclone is because we don’t have a category 6, but we might need one in the future.”

New Zealand’s MetService classifies a Category 5 cyclone as wind speeds from 133 to 142 miles per hour. NOAA says a Category 5 hurricane has sustained wind gusts of 157 miles per hour or higher.

Different countries have slightly different wind speed rankings depending on how long they take measurements for — New Zealand averages wind speeds over 10 minutes, while the U.S. averages them over one minute.


So, will we need a new hurricane scale? Hurricane experts disagreed with Shaw’s claim.

For starters, adding hurricane categories higher than five would force meteorologists to reorganize the entire scale, and force experts to reanalyze past storms to see where they fell on the reworked scale. Many past storms would qualify as higher than Category 5.

“There have been historically many very intense storms that would qualify as Category 6 or even Category 7,” Cato Institute atmospheric scientist Ryan Maue told The Daily Caller News Foundation.

Maue said extrapolating out the Saffir-Simpson scale would have made Hurricane Irma a Category 6 storm. Super Typhoon Meranti would have been a Category 6 and Hurricane Patricia would have been a Category 8.

Maue also took issue with Shaw’s claim that tropical cyclones were getting stronger because of man-made warming. Maue said “there is no convincing evidence in our observational record that global tropical cyclone intensity has increased to the point of needing to add another category.”

“That’s just hyperbole by folks who should know better,” Maue said.

There’s also another problem, which is probably the most important one.

Changing the Saffir-Simpson scale would change perceptions of risk. Category 5 is currently the highest ranking — strongest — storm on the scale because it’s able to cause tremendous damage.

Adding more categories to wind speed scales would make a Category 5 look less severe, lulling the public into a false sense of complacency when they should be evacuating or preparing.

Massachusetts Institute of Technology hurricane expert Kerry Emanuel gave a succinct explanation of how, while the Saffir-Simpson scale is imperfect, changing it would be counter-productive.

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