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Abstract

Global warming increases available sensible and latent heat energy, increasing the thermodynamic potential wind-intensity of tropical cyclones (TCs). This causes a shift in mean TC intensity, which tends to manifest most clearly at the greatest intensities. The Saffir-Simpson scale for categorizing damage based on the wind-intensity of TCs was introduced in the early 1970s, and remains the most commonly used metric for communicating to the public the level of hazard that a TC poses. The scale does not extend beyond category 5 (70m/s windspeed or greater) partly because it was believed that exposure to category 5 winds would cause such great damage to structures that further damage beyond this becomes less relevant. This belief was based on building codes and practices of the day. Here, we propose an extension to the Saffir-Simpson scale to include category 6 TCs, and describe the frequency of TCs, both past and projected under global warming, that would fall under this category using three different approaches. We find that a number of recent storms have already achieved this category 6 intensity and, based on multiple lines of evidence, more such storms are projected as the climate continues to warm.