Hurricane Katrina was one of the worst natural disasters of my lifetime. On the morning of August 29, 2005, Katrina slammed into the Gulf Coast near New Orleans, Louisiana. This massive storm measured about 400 miles in diameter. Hurricane intensity is measured on the Saffir-Simpson Hurricane Scale based upon sustained wind velocity. A storm reaches hurricane strength when its maximum sustained winds reach 74 mph. Storms with winds ranging from 74 to 95 mph are designated Category 1 and typically produce modest damage. The strongest hurricanes on the Saffir-Simpson scale are designated Category 5 with sustained winds exceeding 157 mph. Katrina strengthened to a Category 5 storm as it crossed the Gulf of Mexico with sustained winds reaching an astonishing 175 mph. The storm’s intensity somewhat lessened by the time it made landfall to Category 3 with winds of 125 mph.
Thanks to modern weather satellites, meteorologists were able to warn people along the Gulf Coast that a major storm was imminent. The day before Katrina arrived, New Orleans mayor Ray Nagin issued a mandatory evacuation order – the first in the city’s history. It’s estimated that about 80% of the city’s population heeded the evacuation order. However, many were unable or unwilling to vacate the area. The day before the storm hit, the National Weather Service stated ominously, “Most of the area will be uninhabitable for weeks…perhaps longer.”
The city of New Orleans – with a population of around 500,000 at the time – was especially vulnerable to hurricanes with their powerful storm surge and heavy rainfall. Much of New Orleans is below sea-level. The Army Corps of Engineers had built a system of seawalls and levees to prevent New Orleans from flooding. Some of these levees were quite sturdy but tragically others were not. Katrina brought a monstrous storm surge of up to 27 feet. Engineers knew that such a storm surge would cause some flooding by temporarily exceeding the height of the levee system. What they didn’t anticipate was that the force of the storm surge would breech some levees completely, resulting in devastating and prolonged flooding. More than 80% of the city of New Orleans suffered significant flooding which lasted for weeks. Substantial parts of New Orleans were under so much water that people desperately climbed onto roof tops or were trapped in their attics. The Coast Guard heroically managed to rescue thousands, but despite the efforts of rescuers more than 1,800 people lost their lives. The storm caused a stupendous $125 billion in damages.
One of the most frequent claims we hear today is that global warming is causing more frequent and intense hurricanes. This claim seems quite plausible. Most everybody knows that hurricanes are fueled by warm waters. If global warming is causing an increase in water temperature, it makes sense that this phenomenon would fuel larger, more frequent and more dangerous storms. But what does the evidence say?
In 2014, a group of federal scientists (called the US Global Change Research Program, or USGCRP) published an influential report entitled National Assessment of Global Climate Change Impacts on the United States. This report claimed that there was a strong upward trend in hurricane activity in the North Atlantic Ocean. Their conclusion was based upon a metric called the “power dissipation index,” which measures the cumulative strength of all hurricanes based on maximum wind speed and duration. Strangely, the authors of the report limited the time frame of their study from 1970 until 2009.
Yet more data was readily available. Dr. Ryan Maue calculated the power dissipation index for North Atlantic hurricanes going back to 1920 and including the most recent data through 2013. Dr. Maue’s data, plotted below, gives us a much better understanding of overall hurricane activity in the North Atlantic. The red portion of the graph is the limited data included in the 2014 National Assessment report. It’s not difficult to see how this cherry-picked data would misleadingly suggest that global warming is driving increased North Atlantic hurricane activity. Thankfully, we can look at the big picture and correctly conclude that there is no discernable trend at all. You can see why the authors excluded the most recent data: the four North Atlantic hurricane seasons from 2010 through 2013 had relatively lower hurricane activity. Anyone paying attention to the news knows that the number and strength of North Atlantic hurricanes varies considerably from year to year. But over the last century, overall North Atlantic hurricane activity shows no signs of significant change.
For those of us living in the United States, North Atlantic hurricanes understandably get most of the attention. These are the hurricanes which threaten the big cities along the East Coast and the Gulf of Mexico. But North Atlantic hurricanes account for only 15% of hurricane activity globally. What can we learn by studying world-wide hurricane activity? Scientists have not always been able to accurately track hurricanes around the world. Some storms never make landfall and therefore do not inflict any damage. They remain out to sea, sometimes away from shipping lanes or other human contact. However, the advent of weather satellites in the last 40+ years has allowed scientists to comprehensively track and catalog storms. Dr. Ryan Maue has intensively studied hurricane activity globally. His data is presented in the graph below. This graph plots the total number of hurricanes as well as the number of major hurricanes – those storms classified as Category 3 or greater on the Saffir-Simpson Scale. Again, as even amateur weather watchers know, the number of storms varies considerably from year to year. But the data of storm frequency has been remarkably stable. You read that right – after more than 40 years of climate hysteria, the frequency of global hurricanes has not changed.
Now of course not every strong storm becomes a hurricane. We’ve noted earlier that a storm is not classified as a hurricane unless it produces sustained winds exceeding 74 mph (64 knots) Storms with sustained winds between 39-74 mph (34-63 knots) are classified as “tropical storms.” The graph below shows the total number of tropical storms worldwide dating back to 1970. (The graph also includes the total number of hurricanes plotted below in grey. This is the same data plotted above in blue.) Again, the numbers are very clear. The frequency of tropical storms has shown no significant change over the last 50 years.
But the frequency of hurricanes is not the only measure of hurricane activity, even though we’ve also accounted for the frequency of major hurricanes too. To thoroughly evaluate the total intensity of hurricanes, scientists have developed metrics to measure total hurricane strength. One of those metrics is the power dissipation index described above. A very similar metric is called the “accumulated cyclone energy.” (Note: a “tropical cyclone” is another name for a hurricane.) Like the power dissipation index, the accumulated cyclone energy is calculated based upon maximum wind velocity and duration. This is the best tool we have to assess hurricane intensity. Below is Dr. Maue’s graph of accumulated cyclone energy over the last 50+ years. Again, there is some variability over time – but the overall data shows no upward trend at all. In fact, from 2007 until 2015, there was a period of very low hurricane intensity even while our media and politicians were telling us that climate Armageddon was bearing down upon us.
You certainly don’t need to be a climate scientist with a Ph.D and lots of peer-reviewed publications to reasonably interpret this data. Based on the hysterical climate alarmism that dominates much of our media and political discourse, I think most Americans would be shocked to learn that the frequency and intensity of hurricanes and tropical storms shows absolutely no upward trend over the last 40+ years. Yet many media and political figures have repeatedly proclaimed with utter certainty that global warming is responsible for the powerful storms ravaging our coastlines. They attack and denigrate those who disagree with their viewpoint. It is really quite astonishing how successful climate alarmists have been in deceiving so many people.
Despite their failure to predict the arrival of climate Armageddon over the last 40 years, climate alarmists seem undeterred. They continue to predict massive “superstorms” in the future which will devastate our coastlines and inundate our cities. It seems that for climate alarmists, disaster is always lurking right around the corner but never actually arrives. Now some reasonable scientists do think that future warming might fuel very slightly stronger hurricanes. Such predications about the future should be taken with a huge grain of salt, considering the very poor history of past predictions. (Remember all those climate models which consistently predicted far more warming that we have observed?) But let’s give them the benefit of the doubt for the moment, and say that hurricanes really do become stronger. But would this be the end of the world? Hardly.
Chris Landsea holds a Ph.D. in Atmospheric Science from Colorado State University. He is a widely respected meteorologist currently working at the National Hurricane Center. Dr. Landsea’s studies indicate that future warming may result in hurricanes with 1% greater intensity than before. In other words, major hurricanes would have wind speeds only 1-2 mph greater than they would have otherwise. A future hurricane might have maximum sustained winds of 162 mph, rather than 160 mph. A major storm like this would potentially inflict serious damage and result in loss of life. But the additional hurricane intensity would be negligible.
Attempting to cut fossil fuel use in order to drastically reduce carbon emissions is the absolutely worst way to help people threatened by hurricanes. Many politicians and media figures advocate spending trillions of dollars on expensive and unreliable wind and solar energy, despite the fact that hurricane frequency and intensity has shown no change. Yet the best hurricane strategy is economic growth. Prosperous nations enjoy advance warning systems, durable buildings and infrastructure, strong sea walls and levees, and robust disaster response efforts. The reason that hurricane Katrina was so shocking to Americans is that it was the exception to the rule. Americans generally don’t have to worry about such storms in the same way that people in the developing world do. Hurricanes striking developing nations can be utterly catastrophic, killing many thousands and causing economic devastation which lingers for years or even decades. The best way to help protect people from hurricanes is pursue strategies which encourage economic growth and development. And yes, that means they should use more fossil fuels to build up their society in the same way we have. The real threat from hurricanes comes from the climate alarmists who would waste trillions of dollars on ineffective policies all while denying people in the developing world the same blessings which we enjoy.
Here are some take home points. (1) Yes, the earth’s climate has been gently warming – a trend which goes back to the end of the Little Ice Age more than 300 years ago. (2) Yes, human industry has been causing rising levels of carbon dioxide in our atmosphere, especially since the end of World War II in 1945. (3) Yes, carbon dioxide is a greenhouse gas which we would expect to have a slight warming effect. (4) But the same natural forces which have caused warming since 1700 are still at work today. It is most likely that only a small amount of our present day warming is attributable to human CO2. (5) The gentle warming we have experienced has been overwhelmingly positive – both for humanity and for the rest of creation. (6) Moreover, there is absolutely no evidence that warming has resulted in any change in the frequency or the intensity of global hurricanes over the last 40-50 years. Those who hysterically claim otherwise are truly producing a tempest in a teapot. Hopefully we can change their minds, but even if we can’t, it’s vital that we try and keep the tempest in the teapot. Costly climate policies have already done serious harm for no benefit. Contemplating future massively expensive climate policies are the real storm which threatens the well being of people around the world.
