Sustained winds of over 110 miles per hour move a hurricane into category-3 status. At 157 miles per hour, the storm becomes a category-5 event. The chance that a hurricane develops into a category-3 storm has risen over 30 percent in the past four decades. This increase in frequency makes hurricanes more dangerous than 40 years ago.
Scientific analysis determining long-term trends relies on observations and data collection over time. A single event does not define a trend. When politicians or newscasters point to a surge of cold weather in the mid-western USA and then say it proves global warming is a hoax, they are demonstrating their lack of understanding about climatic trends. Average global temperatures rose one degree Celsius between the mid 20th century and today; global warming is a fact. However, some areas, like the mid-west, experienced colder weather than normal. An average is just what it says, and it includes places like the Arctic where temperatures rose 6 degrees and the USA Northern Plains where 2019 was colder than in the 1960s.
One observation from analyzing 40 years of hurricane data is that the frequency of category-3 storms has increased since the 1980s. This observation doesn’t mean that every hurricane is stronger or that there will be more category-3 hurricanes every year. But it does mean that category-3 storms are more likely in any given year, and that storm intensity is increasing on a decade-by-decade basis.
The recipe for a hurricane is warm water, moist air, and a low-pressure center (converging winds). Heat is the critical enabler for hurricane development. So, as winds sweep across the ocean’s surface, they suck up heat energy from the warm waters. Physics dictates that warm air holds more moisture, so the winds become saturated with water. But warm air also rises, and this moist, water-saturated air ascends due to buoyancy. Winds then converge on the low-pressure area created by the rising air, and a tropical storm is born.
Tropical storms grow up to become hurricanes, and the more heat a storm draws from the ocean, the stronger it becomes. So, heat transfer from the sea to the air is the critical connection between global warming and increasing hurricane intensity. Remember that the atmosphere is not the only recipient of global warming; ocean temperatures also rose over the past 40 years. These warmer seas translate to more storm energy.
When hurricane Katrina literally rained down destruction on New Orleans, the heat was to blame. The hurricane gained strength over the Gulf of Mexico waters that were several degrees warmer than usual. Warming oceans make hurricanes more dangerous, and thus the social and economic impact of these storms on coastal cities increases.
The human effects
The danger posed by natural disasters, hurricanes included, is directly related to its impact on humans. A category-5 storm that begins and ends over open ocean waters poses little threat. However, a category-3 hurricane heading directly towards Miami is a dangerous storm.
Hurricane research into long-term trends has also revealed several other disturbing observations. Hurricanes and tropical cyclones are reaching farther towards the poles. These storms are moving farther north or south from the equator, affecting coastal populations that have traditionally experienced hurricanes via the news only. They now have a front-row seat for the show.
Changes in the climate also cause hurricanes to move more slowly once they reach land. This slowing of the storms increases the occurrence of massive flooding as rain inundates coastal areas for longer periods. Intense flooding like Houston experienced with hurricane Harvey will become more common.
The changing behavior of hurricanes is not mere speculation or hand-waving. Our changing climate makes hurricanes more dangerous. The increased frequency of intense storms and their propensity for more flooding as they make landfall are borne out by four decades of scientific observations.
The warmest decade (Source: ArcheanWeb) – https://archeanweb.com/2020/05/25/the-warmest-decade/ Also:
Ocean warming dwarfs atmospheric warming (Source: ArcheanWeb) – https://archeanweb.com/2020/01/21/ocean-warming-dwarfs-atmospheric-warming/ Also:
Water vapor amplification and global warming (Source: ArcheanWeb) – https://archeanweb.com/2020/02/12/water-vapor-amplification-and-global-warming/ Also:
40 Years of Data Confirm Hurricanes Are Getting Stronger. Climate Models Were Right (By CARLY CASSELLA; Science Alert) – https://www.sciencealert.com/hurricanes-really-are-getting-stronger-and-there-s-a-likely-human-fingerprint Also:
Long-term data show hurricanes are getting stronger (Source: University of Wisconsin-Madison) – https://phys.org/news/2020-05-long-term-hurricanes-stronger.html Also:
Fuel for the Storm (Source: NOAA) – https://oceantoday.noaa.gov/fuelforthestorm/ Also:
Feature Image: Hurricane Isabel (Modified) – By Image courtesy of Mike Trenchard, Earth Sciences & Image Analysis Laboratory, NASA Johnson Space Center. – http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=12140, Public Domain, https://commons.wikimedia.org/w/index.php?curid=625449