The incredible destruction wrought by Hurricane Harvey on Texas, as well as that from Hurricanes Irma and Michael – reminds us of the unbelievable havoc and misery that hurricanes and tropical storms can wreak. The fury accompanying these three storms has raised an obvious and important question: is climate change making hurricanes worse; and isn't this an important reason to take action on climate change?
I definitely believe in human-induced climate change, and I also strongly suspect that climate change may well be making hurricanes at least somewhat worse. But if we want to try to reduce the tragic impact of hurricanes, focusing on climate change is at best a distraction in the effort. Let me explain how I come to what is probably an unexpected conclusion.
Before going any further, let's consider why climate change might be making hurricanes and tropical storms worse. The two key reasons are water temperature and water vapor in the air. Hurricanes gain their energy from warm ocean temperatures. In fact, a hurricane can only form if the water temperature is at least approximately 80 degrees Fahrenheit (26.6 degrees Celsius). It can only be sustained with warm water temperatures. The warmer the temperature, the greater the chance of a hurricane forming and/or strengthening. Global warming certainly appears to be increasing water temperatures. At the same time, higher temperatures tend to increase the amount of water vapor in the air, something else that helps nurture a hurricane and make it more destructive. So other things being equal, global warming may well be contributing to the problem both of the number and intensity of hurricanes and tropical storms.
Yes, but it isn't so simple. Let me explain why.
First off, even if we could somehow end the problem of global warming and associated climate change, it's not clear what impact there would be on the number of hurricanes or their intensity. We know this for no other reason that there were intense hurricanes before there was evidence of global warming. In fact, since the start of the 20th century, the USA has experienced a Category 5 hurricane about once every 25 – 30 years: one in 1900, one in 1935, one in 1961, one in 1969, one in 1992, and now one in 2017. Category 4 hurricanes are an even more frequent occurrence. Table 1 below shows a list of the most intense Atlantic basin hurricanes over the past century. Hurricanes such as the 1900 Galveston storm, the 1935 Florida Keys storm, Carla, and Camille were likely just as intense as Irma and Katrina, and all occurred before global warming was an issue. So solving the global warming problem is certainly not going to eliminate these hurricanes. It may reduce the frequency, but even that isn't clear.
Table 1: Past Category 4 and 5 Hurricanes
|
Hurricane |
Year |
Windspeed (Miles/Hour) |
|
Irma |
2017 |
185 |
|
Katrina |
2005 |
175 |
|
Andrew |
1992 |
175 |
|
Camille |
1969 |
175 |
|
Carla |
1961 |
175 |
|
Mitch (did not hit USA) |
1998 |
180 |
|
Rita |
2005 |
180 |
|
Florida Keys |
1935 |
185 |
|
Gilbert (did not hit USA) |
1988 |
185 |
|
Wilma |
2005 |
185 |
|
Allen |
1980 |
190 |
|
Galveston hurricane |
1900 |
Unknown Cat 5 |
But the intensity of the hurricane really isn't the thing we should be worried about anyway. Instead, deaths and injuries, as well as the resultant damage, are the real concern. After all, there have actually been a number of extremely intense hurricanes in the Atlantic that never touched land. Nobody remembers the names of those storms, and nobody really cares.
So which storms have actually been the deadliest and costliest? The deadliest by far was the 1900 Galveston hurricane, which killed an estimated 6,000 people. They had virtually no warning on that one. Fortunately, modern technology has helped to provide better warning, with much less loss of life. The 1926 Miami hurricane killed 372 people, mainly because people didn't understand the calm of storm's eye is but a precursor to another round.
Then there's property damage. Table 2 shows a list of the most costly hurricanes and tropical storms. One interesting thing to note is that amongst the costliest were storms that weren't intense. In fact several of them – Tropical Storm Allison and Superstorm Sandy - weren't even hurricanes. They did incredible damage, however, and besides fatalities and injuries, that's what really gets our attention.
Table 2: Costliest Hurricanes/Tropical Storms
|
Hurricane |
Year |
Estim Cost (Billion USD) |
|
Hugo |
1989 |
7.1 |
|
Jeanne |
2004 |
7.6 |
|
Tropical Storm Allison |
2001 |
9.0 |
|
Frances |
2004 |
9.5 |
|
Rita |
2005 |
12.0 |
|
Charley |
2004 |
15.1 |
|
Irene |
2011 |
7.3 |
|
Wilma |
2005 |
21.0 |
|
Andrew |
1992 |
26.5 |
|
Ike |
2008 |
29.5 |
|
Superstorm Sandy |
2012 |
71.4 |
|
Katrina |
2005 |
108 |
|
Harvey |
2017 |
100+ |
Our real concern shouldn't be how intense the storm is, it should be how much loss of life (and injuries), as well as the damage. To deal with those, there are three things we can focus on. Let's consider each of them.
The first is the technology associated with tracking storms and predicting where they'll go. The 1900 Galveston hurricane killed so many people because there was little technology to track the storm and warn people to get out. We can and should continue to improve this technology, but we're not likely to have much impact here. Yes, we can build ever better weather satellites and sensors, but such improvements will probably have only marginal impact.
Instead, we should give greater attention to the second area where we can improve – building technology and building codes. The destruction caused by Hurricane Andrew in 1992 led to a detailed review of building codes and practices. They were strengthened significantly, especially with respect to window and door technologies, as well as methods to insure that roofs won't blow off. Homes and businesses built since 1992 are far more likely to survive an intense hurricane, thanks to the Andrew-induced changes. More obviously can be done in this area, particularly in retro-fitting existing structures.
While spending on hurricane tracking and building technologies can help save lives as well as reduce property losses, there is a third area that will yield substantially greater reductions in deaths, injuries and property damage … and it has absolutely nothing to do with global warming or technology. Instead, it has to do with zoning and insurance.
The biggest single danger in a hurricane or tropical storm is storm surge. The low barometric pressure associated with a hurricane causes the ocean to rise at least a few feet. The lower the air pressure, the greater the surge. How do you avoid this problem? By either not building structures in low lying areas adjacent the ocean, or building the structure high enough that storm surge passes underneath the structure.
This isn't some great new revelation – it's been known for at least fifty years. The other thing that's been known for many years is what areas are susceptible to storm surge and flooding. So you may ask, if we know that storm surge is a problem, and we also know where it could be a problem, why haven't we solved the problem?
The answer, unfortunately, is that we don't want to acknowledge the problem. Not only that, we take active measures through our government to make the problem worse. Let me explain how, and why.
We have pretty detailed maps that show what areas in the country will flood, as well as the estimated frequency of flooding. This is quite well known for coastal areas, especially low lying coastal areas. You may ask, if we know the relative frequency that these low lying coastal areas will flood, why do we build structures in those areas?
It's a good question. Some say we shouldn't build structures in low lying coastal areas for this very reason. One way to solve the problem is through property insurance. Unfortunately, about fifty years ago, property insurers concluded that flood insurance simply wasn't a good product to sell. This is because the property insurers calculated they would have to pay out too many claims and wouldn't be able to make money.
To the rescue came the US government, which decided to provide insurance companies guarantees for the flood insurance policies they wrote. This helped foster the development of property in flood prone areas, including areas subject to hurricane storm surge. Lots of people were happy about this – property developers, because they could build beautiful beach front developments; and buyers. So what could go wrong? Plenty.
Remember that the reason the Federal government started guaranteeing flood insurance policies was because the private market wasn't working. By getting involved in flood insurance, there have been a whole host of unintended consequences. The key one is that a huge amount of development has occurred in these flood prone areas. Every time a hurricane or tropical storm hits, huge claims need to be paid. The real reason the costs in Table 2 are so high is because these storms did serious damage to structures that were principally located in flood plains. The 1926 Miami hurricane, a pre-global warming storm, killed lots of people and did a lot of damage. If the same storm occurred today, it's estimated it would cost $ 164 billion in damages. This is because of so much development, as well as lots of it in flood prone areas.
Unfortunately, the problem just gets worse, because we keep permitting development in known flood plains; and that development is backstopped the Federal government.
We probably can't do much about reducing the number of hurricanes and tropical storms we have, at least in the short run, but we can do something about building structures – especially expensive structures – in known flood plains. If we curtailed the number of structures in flood plains, we're likely to reduce storm induced damage there.
We could materially reduce the terrible cost of hurricanes by focusing on items two and three (i.e., improving building codes, zoning, and reducing the amount the amount of construction in flood plains.
Here's the really good news about this. It can all be done without the Paris Climate Accord … without developing any new technology to reduce carbon emissions … and without worrying about who is the President of the United States. Much of it can be done without even spending money.
If it is indeed that easy, why hasn't it been done? Quite simply, because there are lots of incentives to build structures in known hurricane flood plains, but not enough dis-incentives to prevent this from happening. The incentives are obvious: buildings near the sea are highly desirable. Economic development of the beach is highly attractive for lots for people. The disincentives are far less obvious. The big disincentive – paying out Superstorm Sandy size insurance claims – just isn't a disincentive until it happens.
What realistically can be done? At one extreme, we could stop all development in flood prone areas. Pretty draconian, but that would reduce the problem going forward. At the other extreme, we could end all Federal flood insurance guarantees and just let the marketplace sort out the risk. This solution would save taxpayers a lot of money, but it would create problems, especially for lower income groups. Moreover, it would be very unpopular with those whose insurance is presently being subsidized. Any way you look at it, there are tough choices to make. The key point, however, is that these are the real decisions that need to be made if we want to reduce the cost of hurricanes.
This problem isn't limited to construction of properties that are in storm surge prone areas. The case of Houston and Hurricane Harvey is instructive here. The impact of Hurricane Harvey on Houston was not related to storm surge. Even though Houston is a good distance from the Gulf of Mexico, it still has numerous areas that are prone to flooding. Yet there's been lots of development in those areas thanks to government backed flood insurance.
The other thing about Houston is that flooding is a recurring problem. I personally experienced in 25 inch rainstorm in Houston one day in the summer of 1976. It had absolutely nothing to do with a hurricane. The flooding was horrendous. There have been numerous other floods since. The problem is exacerbated by poor soil, excess construction, and inadequate zoning – all problems which are understood, but for which not enough has been done.
Hurricane or no hurricane, these are costly and deadly problems that need to be prevented. My point is that one can superficially cite global warming and climate change as the cause, but by doing so one obscures the real problem: building in flood plains and inadequate building codes.
So while it's important to deal with global warming and climate change, let's not let that be an excuse. When it comes to problems like hurricanes, lets focus attention on solving the real problems.
Please share your thoughts, whether you agree or disagree. Thanks for reading.
