Hurricanes have become so intense in the past decade that some scientists believe we need a new category to better represent their intensity: Category 6.
Under the current Saffir-Simpson Hurricane Wind Scale, hurricanes are categorized on a scale of 1 to 5 based on their maximum sustained wind speed. A hurricane is given Category 5 status when it reaches wind speeds of more than 252 kilometers (157 miles) per hour.
At Category 5 intensity, you can expect significant property damage, including fallen trees and power lines, as well as destroyed homes. Most of the impact area will not be habitable for weeks or months after a Category 5 storm.
In a new study, researchers noted that there have been several storms in recent years that far exceeded this speed threshold. Therefore, they suggest that authorities should consider introducing a new category – Category 6 – to define hurricanes and typhoons with wind speeds of more than 309 kilometers (192 miles) per hour.
Since 2013, at least five storms have already reached the hypothetical Category 6 threshold: Hurricane Patricia, Typhoon Meranti, Typhoon Goni, Typhoon Haiyan and Typhoon Surigae.
For example, Hurricane Patricia struck Mexico and parts of Texas in October 2015. With sustained winds of up to 346 kilometers (215 miles) per hour, it holds the title of the most powerful tropical cyclone ever observed in the Western Hemisphere.
The wind speed of a Category 5 storm compared to five other storms since 2013.
Image credit: James Kossin and Michael Wehner
With climate change already increasing the severity of storms around the world, these types of storms will become increasingly common in the coming years and decades.
Climate change can affect hurricanes and typhoons in numerous ways. Warmer sea surface temperatures provide more energy for hurricanes, potentially leading to greater intensity and faster wind speeds. At the same time, climate change may slow the movement of hurricanes as they drift through geographic regions. This allows the hurricane to lurk over one area for longer, increasing the amount of damage it can cause.
“Anthropogenic global warming has already significantly increased the surface temperatures of the oceans and troposphere in regions where TCs occur [tropical cyclones] form and spread. The resulting increase in available sensible and latent heat energy increases the thermodynamic potential wind intensity of these storms,” conclude Michael Wehner – of the Lawrence Berkeley National Laboratory in California – and James P. Kossin – of the University of Wisconsin-Madison – in their studies.
“Here we introduced a hypothetical extension of the Saffir-Simpson hurricane wind scale to indicate that the most intense TCs are intensifying and will continue to do so as the climate continues to warm,” the study authors add.
Although the proposed storm categorization system has not yet been adopted by the National Oceanic and Atmospheric Administration (NOAA) or any other official agency, it is not the first time researchers have floated the idea of expanding Hurricane Saffir-Simpson. As the climate crisis deepens, it seems increasingly likely that these proposals could become reality.
“This study picks up on a key feature of these classification systems, which is that the most extreme category (5) is open-ended – on this scale, anything above 252 km/h. This is problematic in the context of communicating expected increases in peak hours. The wind speeds of tropical cyclones under climate change. Accordingly, this study examines how the classification of tropical cyclones would change if a Category 6 threshold were introduced at 309 km/h,” said Dr Daniel Kingston, senior lecturer at the University of Otago in New Zealand. was not directly involved in the investigation, a statement said.
“Five storms have already exceeded this hypothetical Category 6 threshold, and all have occurred since 2013 – with the threshold expected to be exceeded with increasing frequency under ongoing climate change,” he added.
The study was published in the journal Proceedings of the National Academy of Sciences