Climate Change is Increasing the Strength and Frequency of Hurricanes

Pro: Hurricanes are Becoming Stronger and More Frequent

Hurricanes have become stronger worldwide during the past four decades, an analysis of observational data shows, supporting what theory and computer models have long suggested: climate change is making these storms more intense and destructive.

The analysis, of satellite images dating to 1979, shows that warming has increased the likelihood of a hurricane developing into a major one of Category 3 or higher, with sustained winds greater than 110 miles an hour, by about 8 percent a decade.

“The trend is there and it is real,” said James P. Kossin, a researcher with the National Oceanic and Atmospheric Administration and lead author of the study, published Monday in Proceedings of the National Academy of Sciences. “There’s this remarkable building of this body of evidence that we’re making these storms more deleterious.”

https://www.nytimes.com/svc/oembed/html/?url=https%3A%2F%2Fwww.nytimes.com%2F2020%2F05%2F18%2Fclimate%2Fclimate-changes-hurricane-intensity.html#?secret=UBjoWpfdjB

While hurricanes are a natural part of our climate system, recent research suggests that there has been an increase in intense hurricane activity in the North Atlantic since the 1970s. In the future, there may not necessarily be more hurricanes, but there will likely be more intense hurricanes that carry higher wind speeds and more precipitation as a result of global warming. The impacts of this trend are likely to be exacerbated by sea level rise and a growing population along coastlines.

Scientists are continuing to refine our understanding of how global warming affects hurricane activity. Cutting edge research is beginning to be able to attribute individual hurricanes to global warming. For example, new research estimates that as the Earth has warmed, the probability of a storm with precipitation levels like Hurricane Harvey was higher in Texas in 2017 than it was at the end of the twentieth century. Because of climate change, such a storm evolved from a once in every 100 years event to a once in every 16 years event over this time period.https://ucsusa.org/resources/hurricanes-and-climate-change

Con: Hurricanes are Not Getting Worse

There has been no increase in hurricanes as the planet has modestly warmed. since the end of the Little Ice Age, around 1850.

Even the U.N. IPCC agrees, finding no increase in the frequency or severity of hurricanes.

  • The United States recently went through its longest period in recorded history without a major hurricane strike.
  • The United States recently experienced its fewest total hurricanes in any eight-year period.
  • Florida, America’s most hurricane-prone state, recently underwent its longest period in recorded history without any hurricanes.

Devastating hurricanes occurred long before the invention of SUVs and coal-fired power plants. And hurricane activity shows little or no impact from global warming. Even the U.N. Intergovernmental Panel on Climate Change 2018 “Interim Report” observes there is “only low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenic influences.” The U.N. observation reflects hurricane and tropical storm data in Figure 1, below.

U.S. Impacts: Hurricane impacts on the United States are at an all-time low. The United States recently went more than a decade (2005 through 2017) without a major hurricane measuring Category 3 or higher, which is the longest such period in recorded history. The United States also recently experienced the fewest number of hurricane strikes in any eight-year period (2009 through 2017) in recorded history. Additionally, America’s most vulnerable state, Florida, recently concluded an 11-year period (2005 through 2016) without a landfalling hurricane of any size—the longest such period in recorded history. The Gulf of Mexico also recently) benefited from its longest hurricane-free period in recorded history (2013 through 2016).

More Wind Shear Negates Warmer Oceans: Whenever a hurricane forms, global warming activists claim modestly warmer global ocean temperatures are allegedly “supercharging” the storms. However, warm ocean water is just one factor in the formation and intensification of hurricanes. Wind shear inhibits strong storms from forming and rips apart storms that have already formed. Scientists have learned that global warming is likely to cause more wind shear in places where hurricanes form and intensify. That is one reason why even the U.N. IPCC admits there has been no increase in the frequency or severity of hurricanes. It is misleading to discuss one factor in hurricane formation (warmer oceans) while failing to discuss an equally important factor (wind shear) that diminishes hurricane formation and intensification.

Finally, it would require several hundred years of detailed hurricane data both before and after 1850 to accurately determine whether the natural trends and fluctuations of hurricane activity have been altered by the 1.3 parts per ten thousand increase in atmospheric carbon dioxide since 1850.  This is the period during which human activity contributed a portion of the increase of CO2 in the atmosphere, most of which occurred since 1940.  Without such sufficient data, no scientific comparisons and conclusions concerning the impact of the tiny increase in carbon dioxide in the atmosphere would be statistically meaningful.

Figure 1: This figure shows global hurricane and tropical cyclone activity are not increasing. Source: Global Tropical Cyclone Activity, Dr. Ryan N. Maue,  http://climatlas.com/tropical/frequency_12months.png.
Figure 2:  Global Hurricane Frequency (all & major) — 12-month running sums. The top time series is the number of global tropical cyclones that reached at least hurricane-force (maximum lifetime wind speed exceeds 64-knots). The bottom time series is the number of global tropical cyclones that reached major hurricane strength (96-knots+). Adapted from Maue (2011) GRL. http://climatlas.com/tropical/frequency_12months.png.
Figure 3: Last 50-years+ of Global and Northern Hemisphere Accumulated Cyclone Energy: 24 month running sums. Note that the year indicated represents the value of ACE through the previous 24-months for the Northern Hemisphere (bottom line/gray boxes) and the entire global (top line/blue boxes). The area in between represents the Southern Hemisphere total ACE.

Recent historically low global tropical cyclone activity: Geophys. Res. Lett. (2011), Abstract:

Tropical cyclone accumulated cyclone energy (ACE) has exhibited strikingly large global interannual variability during the past 40-years. In the pentad since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s. Additionally, the frequency of tropical cyclones has reached a historical low. Here evidence is presented demonstrating that considerable variability in tropical cyclone ACE is associated with the evolution of the character of observed large-scale climate mechanisms including the El Nino Southern Oscillation and Pacific Decadal Oscillation. In contrast to record quiet North Pacific tropical cyclone activity in 2010, the North Atlantic basin remained very active by contributing almost one-third of the overall calendar year global ACE.

From the NOAA GFDL website (Link) : 

“In summary, it is premature to conclude with high confidence that increasing atmospheric greenhouse gas concentrations from human activities have had a detectable impact on Atlantic basin hurricane activity, although increasing greenhouse gases are strongly linked to global warming… Human activities may have already caused other changes in tropical cyclone activity that are not yet detectable due to the small magnitude of these changes compared to estimated natural variability, or due to observational limitations.”

References:

  1. Recent historically low global tropical cyclone activity, Recent historically low global tropical cyclone activity, Geophysical Research Letters, Ryan N. Maue, First published: 20 July 2011, https://doi.org/10.1029/2011GL047711
  2. Global Warming and Hurricanes – An Overview of Current Research Results, Tom Knutson, Senior Scientist, NOAA/GFDL, Last Revised:  Nov. 17, 2023, https://www.gfdl.noaa.gov/global-warming-and-hurricanes/