This season has seen an active Atlantic, most recently with hurricanes Fiona and Ian, leading to loss of lives and causing billions of dollars of destruction in Puerto Rico, Cuba and Florida. Strong tropical cyclones, called hurricanes in the Atlantic, typhoons in the western Pacific, and cyclones in the Indian Ocean, are simple to form, but you need the right mix of conditions: a small atmospheric disturbance in or near a tropical ocean, warm water temperatures (more than 80 F/26.7 C), and uniform winds (high upper-level winds can prevent a storm from forming in the first place, or rip apart a storm that’s already formed). A system goes from a tropical depression to a tropical storm to a hurricane, where the latter consists of winds of at least 74 mph. From there, hurricanes are scaled from 1 – 5 depending on increasing wind speeds. Is climate change making these storms more intense?
The warmer the water temperatures, the more heat energy is available, leading to a higher potential for tropical cyclones to develop. Hurricane Ian grew in intensity as it passed over ocean water 2 – 3 degrees Fahrenheit warmer than normal for this time of year. Why is the water warmer? It’s due to our high emissions of greenhouse gases to fuel the conveniences of modern life. In fact, the ocean takes up the majority of excess heat from human-caused global warming: 90% of it!
A warmer climate also allows hurricanes to unleash more rain. With each degree Celsius (1.8 degrees Fahrenheit) of warming, the atmosphere can hold 7% more water vapor that then gets released as precipitation. Add that water to the storm surge, made worse by rising sea levels, and you have a set-up for large-scale destruction. Data from NOAA show that the water off the southwest coast of Florida has risen more than 7 inches since 1965. It’s the flooding, not the winds that lead to most damage to life and property.
Enter in another scenario: rapid intensification, or, an increase of wind speed of at least 35 mph in 24 hours. We’ve seen this before in hurricanes like Harvey, Irma, Maria and Michael in 2017 and 2018. This year, Ian rapidly intensified multiple times. A study looking at hurricane records in the Atlantic from 1986 – 2015 found rapid intensification increasing 4.4 mph per decade, attributing some of the gains to a shift into the warmer phase of the Atlantic Multidecadal Oscillation (AMO), a natural ocean-atmosphere cycle, in combination with human-caused warming.
Another study, a NOAA 2019 paper, used simulations from one of the most advanced climate models available (HiFLOR), and concluded that recent increases in rapid intensification are “outside HiFLOR’s estimate of expected internal climate variability which suggests the model’s depiction of climate oscillations like the AMO cannot explain the observed trend.”
While natural climate variations play a role in hurricane development, intensity, and frequency, human-caused climate change amplifies these effects. Preliminary analysis of rainfall totals from hurricane Ian has found that the amount was at least 10% higher than expected in a world without warming.
With its sun and offshore wind, Florida could be a leader in renewable energy and the new and profitable jobs resulting from it. It’s a shame that politics are getting in the way of a happier, healthier planet and population.