Hurricanes, also known as tropical cyclones, are powerful, fast-rotating storm systems that can have catastrophic effects on lives, homes, and the environment. A recent publication in the journal Proceedings of the National Academy of Sciences (PNAS) underscores how the effects of climate change are making these dangerous storms more frequent.
As the planet warms, evaporation and heat transfer from the oceans to the atmosphere intensify. Consequently, storms draw in additional water vapor and heat, leading to heightened wind speeds and more devastating hurricanes. This prompts a pressing question: should the most severe hurricanes be designated under a new classification, Category 6?
Currently, hurricanes are rated from 1 to 5 on the Saffir-Simpson Hurricane Wind Scale, which was developed in the 1970s. The purpose of the scale is to communicate risk to the public by classifying storms by their maximum sustained wind speed. The most severe is a Category 5 classification, indicating wind speeds surpassing 157 miles per hour (253 km/h).
Research conducted by climate scientists James Kossin of the First Street Foundation and Michael Wehner of Lawrence Berkeley National Laboratory has focused on analyzing the impact of climate change on the increase of hurricanes with wind speeds exceeding the 157 mph threshold. In their recent paper, they consider the benefits of introducing a new Category 6 that would include hurricanes with sustained wind speeds above 192 mph (309 km/h).
If adopted, this new category would include storms such as 2013’s Typhoon Haiyan, which had wind speeds of around 195 mph (314 km/h) and caused extreme devastation to regions of Southeast Asia, notably the Phillippines. Hurricane Patricia, which struck Mexico in 2015 with maximum wind speeds of 215 mph (346 km/h), the highest ever recorded, would also fall into Category 6.
The debate over Category 6:
- However, is the addition of a new category really needed? Under the current criteria, a Category 5 storm indicates catastrophic damage, rendering an area uninhabitable for weeks or months. Some argue against the need for a classification beyond this level of threat.
- Likewise, the public might underestimate the threat posed by Category 5 hurricanes if the scale were expanded to include Category 6. For example, the devastating Hurricane Irma and Hurricane Dorian would still not qualify based on their wind speeds (185 mph, or 298 km/h). And other Category 5 storms with less powerful winds, like Hurricane Ida, Hurricane Harvey, and Hurricane Florence, still caused tremendous damage due to extreme flooding.
- Scientists and meteorologists have long debated the overall adequacy of the Saffir-Simpson Hurricane Wind Scale in conveying the risks posed by hurricanes, as it overlooks hazards such as coastal storm surge, flooding, rip currents, and tornadoes, all of which can have fatal consequences—often to a greater degree than wind alone.
- Regardless of whether the Saffir-Simpson scale is modified to include a new Category 6 or changed altogether, Kossin and Wehner’s research sheds light on how global warming profoundly impacts hurricane conditions, suggesting we are likely to see an increase in severe hurricanes in the future.
