Stronger and more destructive hurricanes fueled by climate change may require a rethink in how storms are classified. This is according to a new study that proposes the introduction of a Category 6 classification to better represent damaging wind speeds.
The study, published Monday in the journal Proceedings of the National Academy of Sciences, examined whether the existing Saffir-Simpson hurricane wind scale, which rates hurricanes based on a storm's maximum sustained wind speed from 1 to 5, is sufficient to communicate this danger from stronger storms.
“Our motivation is to reconsider how the openness of the Saffir-Simpson scale can lead to underestimation of risk and, in particular, how this underestimation becomes increasingly problematic in a warming world,” said Michael Wehner, senior scientist at Lawrence The Berkeley National Laboratory in California and one of the study's authors said in a statement.
At the low end of the Saffir-Simpson scale, Category 1 describes wind speeds of 74 to 95 miles per hour. At the other extreme, Category 5 is used for storms with winds of 155 mph or more.
Several studies have found that while climate change is unlikely to lead to an increase in the number of hurricanes occurring each year, warmer ocean temperatures will increase the occurrence of such hurricanes. A warmer atmosphere can also retain more moisture, meaning these storms can cause heavier rainfall and catastrophic flooding.
Therefore, the planet can expect more severe storms as long as global warming continues.
In their study, researchers looked at hurricanes from 1980 to 2021 and found that five storms in the last nine years had peak wind speeds of more than 192 miles per hour. Scientists argued that these hurricanes could have been classified as Category 6 storms.
The study also used models to examine how different climate scenarios might affect hurricanes and other major storms around the world. They found that the risk of Category 6 storms in the Gulf of Mexico, a region already prone to strong hurricanes, could double if the planet warms 2 degrees Celsius above pre-industrial levels. Southeast Asia and the Philippines are also among the regions that would face a similarly high threat from intensified storms, the researchers found.
“Even under the relatively low global warming targets of the Paris Agreement, which aims to limit global warming to just 1.5 [degrees] “C above pre-industrial temperatures by the end of this century, the increased probability of Category 6 storms is significant in these simulations,” Wehner said in the statement.
The findings contribute to ongoing debates about how to better communicate to the public the threats posed by extreme weather events and the ways in which climate change can multiply them.
For example, scientists know that the Saffir-Simpson scale cannot capture some of the most destructive and potentially deadly aspects of a hurricane, such as storm surge, rainfall and flooding.
“Adding a sixth category to the Saffir-Simpson hurricane wind scale would not solve this problem, but it could raise awareness of the dangers of increased risk of severe hurricanes due to global warming,” said study co-author James Kossin , a climate scientist and distinguished science advisor to the First Street Foundation, a nonprofit research group, said in a statement.
The National Hurricane Center said Tuesday that it will begin releasing a new experimental tropical storm forecast this summer, updating its existing cone graphics that show a storm's potential track. The new forecasts will include tropical storm and inland hurricane watches and warnings in effect to better represent inland wind risks during extreme weather events, the agency said.
