As the oceans and atmosphere have become warmer, the intensity of hurricanes has increased. A study has suggested that the climate crisis has caused a degree of intensification in the strength of hurricanes that necessitates an entirely new category.
Hurricane strength is usually measured using the Saffir-Simpson scale, developed in the 1970s by Herbert Saffir and Robert Simpson. According to the widely used metric, hurricanes are categorized in order of ascending wind speeds and storm surge intensity.
Category 1 hurricanes are the weakest category of storm, with the scale going all the way to Category 5. Hurricane Katrina, which hit New Orleans in 2005, and Hurricane Maria, which devastated Puerto Rico in 2017, were all Category 5 hurricanes. The most damage done by hurricanes is due to severe rainfall and coastal flooding.
“Storms are getting stronger and stronger, so category 5 underestimates actual risk,” claimed James Kossin, an author of the study and an atmospheric scientist at the University of Wisconsin–Madison.
The study, published in the Proceedings of the National Academy of Sciences, and titled The growing inadequacy of an open-ended Saffir–Simpson hurricane wind scale in a warming world, suggests “considering the extension to a 6th category of the Saffir–Simpson hurricane wind scale to communicate that climate change has caused the winds of the most intense TCs (tropical cyclones) to become significantly higher.”
According to the study, 5 hurricanes in the last decade have met the proposed criteria for qualifying as a Category 6 storm, which includes minimum sustained wind speeds of 192 miles per hour.
The study identifies global warming, the key phenomenon leading to the climate crisis, as the cause of stronger hurricanes. “Global warming has increased the energy available for tropical cyclone intensification through increases in latent and sensible heat fluxes from warmer ocean temperatures. As a result, storm intensities well above the category-5 threshold are being realized and record wind speeds will likely continue to be broken as the planet continues to warm. In light of this, we introduce a hypothetical modification of the Saffir–Simpson hurricane wind scale to bound category 5 to peak wind speeds between 70 and 86 m/s and include an additional category 6 above that.”
The climate crisis is not only causing stronger hurricanes, but making them more frequent. Another study from 2022 suggested that extreme hurricane seasons in the Atlantic Ocean are twice as likely as they were in the 1980s, owing to the climate crisis.