Hurricanes are devastating weather anomalies and the winds and flooding that come in their wake can cause untold amounts of damage to coastal cities and towns. Thanks to the availability of 24-hour news networks and the Internet, we’ve all seen the brutal evidence of such storms.
Recently, hurricanes like Florence and Katrina, and superstorms like Sandy, have had many people wondering if there is some correlation with the incidence of these destructive storms and the rise in global warming. But, is this potential link between the two phenomena scientifically sound, or is it simply posturing by environmentalists?
Hurricane Florence recently blew its way through the Caribbean and hit the southeast coast of the U.S. Between August 31 and September 19, 2018, the eventual Category 1 storm poured trillions of gallons of rain onto the Carolinas, resulting in massive amounts of flooding. The storm reached a peak of 140 mph and ended up causing the deaths of 45 people.
Sandy and Katrina
Compared to Superstorm Sandy in 2012, a category 3 storm and Hurricane Katrina in 2005, a category 5, Florence was a light drizzle. Nevertheless, even a smallish hurricane can cause a significant amount of damage and loss of life. But why have storms like these been so destructive in recent years? Could it be due to climate change?
To understand the impact of global warming on hurricanes, we first need to understand hurricanes themselves. If one looks at a basic definition, they see that hurricanes form when areas of disturbed weather, mostly rain, and thunderstorms, organize over the ocean in a swirling pattern. As winds increase, they end up extracting more and more energy from the ocean water below.
Size of a Storm
The strengthening storms are then carried along by even larger weather patterns and travel along those pathways; sometimes out to sea and sometimes to shore. Nevertheless, hurricanes can be as large as 300 miles across, which means they can encompass quite a lot of land mass within them.
There has, of course, been tons of research done on whether or not tropical hurricanes will increase in strength and numbers in the coming years thanks to global warming. Unfortunately, much of the information is inconclusive or contradictory. Nevertheless, one only need to look at the facts to see how a warmer climate might result in bigger, better hurricanes.
Storm Expert David S. Nolan has been studying weather at the University of Miami and is acting chair of the department of atmospheric sciences. He also happens to be a noted expert on hurricanes and tropical weather in general. He recently weighed in on the notion of hurricanes and climate change in an interview with NBC News.
Nolan begins by explaining how hurricanes are categorized from 1 to 5 by the National Oceanic and Atmospheric Administration or NOAA. Category five hurricanes have the most severe wind speeds and are generally the most instructive. Category ones are still forces to be reckoned with, but by no means the most dangerous.
A Sixth Category?
Category fives are exceptionally rare and can reach speeds of up to 170 and 180 mph. Nolan posits that even if the weather continues to warm on a global scale, category fives will still be an extremely rare occurrence; maybe once every five years instead of once every ten. He adds that sixth category, meaning winds exceeding 180 mph is just as unlikely.
Nolan explains that there are some favorable conditions necessary for hurricanes to form. The first of which is warm ocean temperatures above 85 degrees Fahrenheit. This explains why so many hurricanes form in tropical waters. Category fives only form in these very favorable conditions, and again, rarely.
Hard to Predict
Predicting hurricanes, or rather predicting where a hurricane’s path will take it, is still a difficult enterprise for scientists like Nolan. It is a science, though not an exact one. Nevertheless, hurricane prediction and tracking have improved greatly thanks to the availability of satellite imaging. There are even drones that can fly out into storms and measure metrics.
Some hurricanes, like Florence, can make landfall quickly and dissipate soon after, causing little damage. Hurricane Harvey in 2017, however, hit land and gave way to heavy rainfall and coastal flooding. But predicting what course a storm takes relies on two important factors, which Nolan was happy to lay out in his recent interview.
The first factor to determine the course a hurricane takes is to see whether or not the storm is moving steadily inland, or lingering off the coast. Scientists like Nolan determine this by looking at the steering patterns of the atmosphere around the hurricane. This essentially means watching the larger weather patterns around the large storm.
The second factor depends on the kind of terrain the storm is heading towards or sitting over. If the ground is rough, the hurricane becomes disrupted. Nolan uses Hurricane Harvey as an example. It sat over Houston, which is a relatively flat and smooth surface near the Gulf of Mexico. As such, Harvey didn’t dissipate quickly but lingered for a number of days.
As to the subject of climate change, Nolan offered an educated take on the swirl of theories. There is evidence that the changing global weather patterns are making for more extreme rainfall. This can be explained by the warmer weather in general. Warm air can hold more water vapor, which rises and forms clouds and subsequently rain.
Regardless of the warmer weather and increased rainfall, Nolan suggests that, based on the current trends and our current understanding of hurricanes, there is no evidence as of yet to indicate that hurricanes may become more frequent or severe in the next few years. Of course, modern hurricane records, the good quality ones anyway, only go back about 60 years.
Thus, as hurricane activity varies so much from year to year, it hasn’t really been long enough in the grand scheme of things to see an increasing trend that is backed by scientific evidence. Weather changes can happen over centuries before upward trends are shown to be any sort of significant.
Nolan has said that he and his fellow atmospheric scientists have been using computer models for years in an attempt to simulate the motions of the atmosphere. It is through this method that they can more accurately assemble digital images of current weather and extrapolate how it might change in time; using the laws of physics and mathematics.
Indeed, most of Nolan’s research has been about hurricane formation and fostering a better understanding of the physical processes by which this phenomenon occurs. He added that of the many “disturbances” in the oceans every summer, very few become hurricanes. Nolan just wants to understand why some do.
The term “rapid intensification” has been thrown around a lot in scientific circles when it comes to the way hurricane wind speeds increase. This is essentially studying how hurricanes can increase by two or more categories in a single day. If Nolan and his peers learn how this happens on a small scale, they may be able to predict it happening on a larger scale as well.
No Proof, Yet
Ultimately, the main understanding of the scientific community is that global warming and climate change have little to no effect on the frequency of formation or intensity of hurricanes at present. That’s not to say that we may not see some changes in the future, but as Nolan explained, it will be a long while before scientists can truly measure the correlation with certainty.