4 Ways Hurricanes Are Different as a Result of Climate Change

Satellite image of Hurricane Florence


As Hurricane Florence makes her way across the Carolinas, we at Mothers Out Front feel deep concern for the people in her path who face a number of life-threatening perils. Eleven people have died three days into the ongoing superstorm. The weather system is moving very slowly at 2 MPH. Twenty-four inches (as I write this) of rain have fallen and more continues to fall. Rivers are expected to crest at up to 40 inches flooding communities. One million people are without power and many are displaced from their homes. People all over are asking, “What is happening?”

Why are the weather forecasters describing this storm as “huge,” “epic,” and “a monster?” And why, once the winds have calmed down, have people found themselves newly at risk? They have had to prepare for days of “catastrophic” rainfall, flash flooding, and slower freshwater flooding, instead of watching the storm move quickly through the region and dissipate. 

What are climate scientists saying about why hurricanes are different now? Four major differences are noted: hurricanes are larger; they are wetter; they produce higher storm surges; and they are more sluggish. These differences can be tied to changes in our climate resulting from the higher levels of greenhouse gases that have been released into the earth’s atmosphere, primarily from burning of fossil fuels. These changes have the power to dramatically increase the intensity and destructive power of the new superstorms and hurricanes that hit our coastlines. Here are four of the changes:

  1. The sea water is warmer, so it provides more energy to hurricanes. The Atlantic, where Florence formed, is 3.6°F warmer than normal. Harvey, which flooded out and destroyed parts of Houston, took shape over the Gulf of Mexico whose waters were warmer by 2°F. Scientists know that warmer water releases more thermal energy into newly forming cyclonic systems, increasing their intensity and wind speed.
  2. The air is warmer, so it holds more moisture. NOAA (National Oceanic and Atmospheric Administration) states that the air temperature (over the contiguous U.S., year-to-date in 2018) is 2.6°F higher the average temperature in the 20th century. Warmer air can hold more moisture evaporating from both land and ocean, leading to huge systems and more rainfall from hurricanes.
  3. Sea levels are rising, so storm surge is worse. Not only is the warming climate melting the great polar ice sheets and causing sea level rise, but warmer water creates more oceanic volume. And for every inch of sea level rise, the storm surge is commensurately greater. In Florence’s case, the storm surge was in the 20 inch range in some areas. The storm surge accompanying hurricanes is considered to be perhaps the most deadly threat to residents of coastal communities.
  4. The jet stream is slowing down and becoming less stable, so hurricanes are becoming sluggish and sometimes stalling. Nature International Journal of Science reported a study showing that the speed with which Atlantic hurricanes move has declined 20% in the period from 1949 to 2016. Recently, some major hurricanes have “stalled” such that the excess water falling as rain over several days has overwhelmed the ability of rivers, streams, and coastal areas to contain it, causing dangerous flood conditions. Scientists are researching changes in upper level atmospheric circulation that have been influenced by climate change to find out how they may be blocking these large storm systems from moving quickly on through. For example, Michael Mann, professor of atmospheric science at Penn State University, has suggested that the warming of the Arctic has led to new jet stream patterns “that are associated with the stalling of weather systems, including what we’ve seen with hurricanes over the past decade like Harvey, Irene, and now Florence.”

In summary, climate change has produced warmer water and warmer air making ocean waters ripe for developing more intense cyclonic systems. Sea level rise increases storm surge, and changed upper level atmospheric conditions are slowing the forward progress of these systems, leading to extraordinarily dangerous amounts of rainfall.

We at Mothers Out Front are focused on ensuring the wellbeing of all children as they enter the climate of the future. We are also focused on the need for justice for frontline communities of less wealthy citizens who often lack the resources to escape or recover from a superstorm.

We are working hard at state and local levels to dramatically curtail the release into the atmosphere of the greenhouse gases that are continuing to cause the climate to warm. We, with our allies, are creating a future in which energy is largely provided by renewable sources of energy (not carbon dioxide-releasing fuels like oil and natural gas). Join us in this important work that will help ensure that all children will have a livable climate.


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