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Rise in Storm Intensity Prompts Calls For a Whole New Category of Hurricane : ScienceAlert

Heat trapped by fossil fuel emissions is causing Earth’s atmosphere to chug with increasing fury. Some winds are now blowing so strongly that researchers propose adding an even more extreme category to the Saffir-Simpson hurricane wind scale.

“As a cautious scientist, you never want to raise hell,” Michael Wehner, a climate scientist at Lawrence Berkeley National Laboratory, told Dinah Voyles Pulver in USA Today. But “the wolf is here.”

The scale the United States has been using since the early 1970s ranges from Category 1, which indicates irritating winds of 120 kilometers (74 miles) per hour, to a harrowing 250 kph (157 mph) or more for the Category 5.

Demolished homes and scattered debris
Damage from 259 km/h Category 5 winds caused by Hurricane Ian that hit Florida on November 7, 2022. (Giorgio Viera/AFP/Getty Images)

Winds this powerful can demolish homes and destroy infrastructure, leaving areas uninhabitable for weeks, if not months. But 150 miles per hour no longer reflects the magnitude at which these storms can blow now, argue Wehner and former climate scientist James Kossin.

“Because climate change increases temperature and humidity, which are the sources of energy for a hurricane or tropical cyclone, one would expect this speed limit to increase,” Wehner explained to Li Cohen on CBS News. “And indeed it does.”

From 1980 to 2021 there has been an increase in storms well beyond Category 5. Therefore, researchers propose expanding the classification system to include Category 6, which would encompass hurricanes with winds of nearly 310 kph (192 mph) or further.

Chart showing hurricane intensity compared to Category 5 extent
Five tropical cyclones in the last 10 years would meet the proposed criteria for a Category 6 storm. (Kossin, PNAS2024)

At least five storms since 1980 would fall into that category, and all of them have occurred in the last nine years alone.

This includes one of the most powerful tropical storms on record, Typhoon Haiyan. In November 2013, this storm hit the Philippines with winds of 315 kilometers per hour, leaving more than 4 million people homeless and killing more than 6,300.

The team’s modeling suggests the Gulf of Mexico would see a doubling of Category 6 storms with about 2°C of global warming above pre-industrial levels, and regions near the Philippines can expect an increase of about 50 percent. hundred.

The current scale is inadequate, the team argues in their paper. At 346 kilometers per hour, Hurricane Patricia, which hit Mexico in 2015, was 97 kilometers per hour faster than the lower limit of Category 5.

“(The existing scale) is problematic in the context of communicating expected increases in the maximum wind speeds of tropical cyclones under climate change,” agrees University of Otago hydroclimatologist Daniel Kingston, who was not involved in the study. study.

Kingston explains that although other regions, such as New Zealand, may not directly experience the full impact of cyclones, the remnants of the storms can still cause wide-ranging devastation, such as the flooding now occurring on the east coast of Australia after a cyclone in the north.

“The most common and widespread impacts of any tropical cyclone are damage caused by water, rain and storm surge,” says Raveen Das, director of the New Zealand Tropical Cyclone Warning Centre. Other researchers agree. that wind speed is not the best reflection of these storm impacts, much less the only measure of their destruction.

While other regions use different cyclone scales, they are also based on wind speed and have similar open upper limits, so meteorologists around the world are watching this discussion with interest.

“While adding a sixth category to the Saffir-Simpson hurricane wind scale would not solve (the problem of storm surge risk), it could raise awareness about the dangers of the increased risk of major TCs due to global warming,” conclude Wehner and Kosiin. .

His research was published in PNAS.

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