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In a warming world, climatologists predict Category 6 hurricanes

Newswise — For more than 50 years, the National Hurricane Center has used the Saffir-Simpson wind scale to communicate the risk of property damage; it denotes a hurricane on a scale from Category 1 (wind speeds between 74 and 95 mph) to Category 5 (wind speeds of 158 mph or greater).

But as rising ocean temperatures contribute to ever more intense and destructive hurricanes, climate scientists Michael Wehner of the Lawrence Berkeley National Laboratory (Berkeley Lab) and James Kossin of the First Street Foundation wondered whether Category 5 would last indeterminate was sufficient to communicate the risk of hurricanes. damage caused by hurricanes in a warming climate. They therefore investigated and detailed their in-depth research in a new article published in the Proceedings of the National Academy of Sciences (PNAS), where they also introduce a hypothetical category 6 on the Saffir-Simpson wind scale, which would encompass storms with wind speeds greater than 192 mph.

“Our motivation is to reconsider how the open nature of the Saffir-Simpson scale can lead to an underestimation of risk and, in particular, how this underestimation becomes increasingly problematic in a warming world,” said Wehner, who has spent his career studying the behavior of extreme weather events in a changing climate and the extent to which human influence contributed to individual events.

According to Wehner, anthropogenic global warming has significantly increased ocean surface and tropospheric air temperatures in regions where hurricanes, tropical cyclones and typhoons form and spread, providing additional thermal energy for the intensification of storms. When the team conducted an analysis of historical hurricane data from 1980 to 2021, they found five storms that would have been classified as Category 6, and all of them occurred in the last nine years of records. They determined a hypothetical upper limit for Category 5 hurricanes by looking at the increasing range of wind speeds between lower category storms.

Hurricanes, tropical storms, and typhoons are essentially the same weather phenomenon; their difference in name is purely geographical: storms in the North Atlantic and Northeast Pacific oceans are called hurricanes, events in the Northwest Pacific Ocean are called typhoons, and events in the South Pacific and Indian oceans are called cyclones tropical.

In addition to studying the past, the researchers analyzed simulations to explore the impact of global warming on the intensification of hurricanes. Their models showed that with global warming of two degrees Celsius above pre-industrial levels, the risk of Category 6 storms increases by up to 50% near the Philippines and doubles in the Gulf of Mexico and that the highest risk of these storms is located in the southeast. Asia, Philippines and Gulf of Mexico.

“Even under the relatively weak global warming targets of the Paris Agreementwhich aims to limit global warming to just 1.5°C above pre-industrial temperatures by the end of this century, the increased risks from Category 6 storms are substantial in these simulations,” Wehner said.

“Messaging about tropical cyclone risks is a very active topic, and changes in messaging are needed to better inform the public about inland flooding and storm surge, phenomena for which a wind-based scale does not help. has only tangential relevance. While adding a 6th category to the Saffir-Simpson Hurricane Wind Scale would not solve this problem, it could raise awareness of the dangers of increased risk of major hurricanes due to global warming,” Kossin said. “Our findings are not intended to propose changes on this scale, but rather to raise awareness that wind risk from storms currently designated as Category 5 has increased and will continue to increase due to climate change.”

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Lawrence Berkeley National Laboratory (Berkeley Lab) is committed to providing solutions for humanity through clean energy research, a healthy planet, and scientific discovery. Founded in 1931 on the belief that the biggest problems are best solved by teams, Berkeley Lab and its scientists have been recognized with 16 Nobel Prizes. Researchers from around the world rely on the laboratory’s world-class scientific facilities to conduct their own pioneering research. Berkeley Lab is a multiprogram national laboratory managed by the University of California on behalf of the Office of Science of the U.S. Department of Energy.

DOE’s Office of Science is the largest supporter of basic research in the physical sciences in the United States and works to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.



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