This is a special article just for the Middle School and High School students out there. I have been informed that the myth that Hurricane Katrina was caused by global warming is still being taught in those schools and that such hurricanes will get worse in the future. This is a great myth, but it is only a myth. It certainly gets told a lot, but just because something is used as political capital does not make it true. This might be one of the biggest lies that just won’t go to sleep. So I am putting together this article to help students debunk the myth that global warming causes hurricanes. I will even proceed on the assumption that increasing CO2 levels will actually cause warming, just to keep it simple.
The myth that global warming causes hurricanes started with Hurricane Katrina. Al Gore really put that on the map with his emotional, but not scientific portrayal in the movie An Inconvenient Truth. The basis for the claim was timing. An article by Webster et al. in Science Magazine came out weeks before Hurricane Katrina hit. That article was based on the idea that warming oceans would cause an increase in hurricanes in the future as a result of global warming.
The timing and the article set off a firestorm of activity within the scientific community. Many scoffed at the idea while others jumped on board. Several studies were undertaken to make a more comprehensive projection. The most recent was by the World Meteorological Organization Expert Team on Climate Change Impacts on Tropical Cyclones and came out in 2010. The summary of the report was given by Dr. Judith Curry.
- Detection and attribution: “It remains uncertain whether past changes in any tropical cyclone activity (frequency, intensity, rainfall, and so on) exceed the variability expected through natural causes, after accounting for changes over time in observing capabilities.”
- Projections: “It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged owing to greenhouse warming. . . Current models project changes ranging from −6 to −34% globally, and up to ±50% or more in individual basins by the late twenty-first century. Some increase in the mean maximum wind speed of tropical cyclones is likely (+2 to +11% globally) with projected 21st century warming.”
So the expert group from the World Meteorological Organization says that they cannot detect any change in the number of hurricanes from normal in the past. So the number of hurricanes remains normal. In addition their prediction is that there will probably be fewer hurricanes, but they might be stronger in some places.
That 5 years after Hurricane Katrina the main meteorological group is saying that they do not detect a change in the number of hurricanes is strong evidence that Hurricane Katrina was a totally natural event. Remember that the main problem was that the levees failed in New Orleans. The flooding from that is what caused the main damage to New Orleans. That happened in the days that followed the hurricane. Mankind caused the disaster in New Orleans, but as a result of not keeping up the maintenance on the levees. Mankind had nothing to do with the hurricane itself.
Dr. Ryan Maue has created a measure of the Earth’s total hurricane energy. He named this the Accumulated Cyclonic Energy. Cyclones are the more commonly used word for hurricanes around the world. Typhoon is another word used to describe the same weather event. Different locations around the world call them by different names. Dr. Maue has the total energy associated with all the cyclones around the world since the early 1970’s. Here is his official chart on the total energy.
There are many ups and downs with the total energy associated with the global hurricanes, but there is no correlation to temperature or CO2 levels. His website states at the very top of the page the following piece of information.
Global Tropical Cyclone ACE does not show an upward trend in communion with global temperatures.
There is the official statement from the professor that measures this. That is about as clear as possible.
I did take the liberty of associating the global CO2 levels with the ACE. Here is what they look like since 1975.
The ACE is comparable to the level in 1980 when CO2 was around 335 ppm, not the 390 ppm it is today. So while CO2 levels are higher, the global energy associated with hurricanes is unchanged. The science and the data both indicate that the increasing CO2 levels are not changing the total energy associated with hurricanes.