Bad weather causes damage. The National Centers for Environmental Information keeps track of weather events that cause over $1 billion in damage. According to the most recent data, such events have increased dramatically over the last 35 years nationwide. The columns in Figure 1 shows the number of billion dollar disasters per year. From an average of 1.8 in 1980-1984, the number has increased to 11.25 for the years 2012-2015. The number peaked in 2011 at 16.
The colors show the kind of disaster. While there used to be roughly equal numbers of several different kinds of disasters, in recent years the number of severe storms has increased (shown in green). Over the last 4 years, 51% of all billion dollar disasters have been caused by severe storms. While one immediately thinks of hurricanes and tropical storms (shown in yellow on the chart), the last 4 years have actually been years of low hurricane activity. The billion dollar disasters are being caused by tornadoes, thunderstorms, and other kinds of severe weather.
The black line in Figure 1 shows the 5-year mean of the dollar value of the damage caused. In the mid-1980s, the annual damages were under $10 billion. Damages peaked at about $70 billion in 2008, and have been running between $50 and $60 billion in recent years. Cost assessments for 2015 have not yet been completed.
The disasters that cause the most dollar damage are those that affect a wide area. The most damaging of all were Hurricane Katrina ($152.5 billion) and Hurricane Sandy ($67.6 billion), mostly through flooding from storm surge.
Why have the number of billion dollar disasters increased so dramatically? There are two principal reasons. One is climate change. Heat is a form of energy. Warm the atmosphere, and you increase the amount of energy in it. Put more energy in the atmosphere, and there is more energy to fuel severe weather. One of the primary predictions of climate change is that the world will experience an increase in severe weather events, and that seems to be happening, in the United States at least.
Another reason is development. Over time, with our expanding population, more and more of the country has been developed, and more of the land has been covered with buildings and infrastructure. When severe weather strikes, it is more likely to hit developed land, causing more damage. Not only that, but we have put ourselves in harms way by moving into vulnerable areas. For example, in St. Louis County, millions of dollars of development has occurred in the area formerly known as Gumbo Flats, now called Chesterfield Valley. Most of the development happened after the Great Flood of 1993. If a flood were to occur in that area now, it would cause much greater damage than in 1993.
The vulnerable areas that have seen development include the seashore, river valleys, forests (fire hazard), and earthquake zones.
Inflation is probably not the major cause of the increase. The NCEI cautions that it is difficult to estimate the current cost of events that happened years ago. However, they have tried, and have adjusted for inflation. Their estimates may not be perfect, but I doubt that inflation is the major cause of the increase.
The next post will look at similar data for Missouri.
National Centers for Environmental Information. 2016. Billion-Dollar Weather and Climate Disasters: Summary Stats. Downloaded 2/9/16 from https://www.ncdc.noaa.gov/billions/summary-stats.