Billion-Dollar Weather/Climate Disasters: Time Series

The graphic below helps to visualize how the different types of identified U.S. Billion-dollar disaster events have changed over time. Caution should be used in interpreting any trends based on this graphic for a variety of reasons. For example, inflation has affected our ability to compare costs over time. To reflect this, the graphic also shows events with less than $1 billion in damage at the time of the event, but after adjusting for Consumer Price Index (inflation), now exceed $1 billion in damages. Continued assessment of these data are in process, as there are other factors as well that affect any rate of change interpretation. Comparison of events in most recent years is most reliable.

Recent milestones to improve the data analysis include the following:

NCDC hosted a workshop in May 2012 including academic, federal, and private sector experts to discuss best practices in evaluating disaster costs. A research article (Smith and Katz, 2013) regarding the loss data we use, our methods and any potential bias was published in 2013. This research article found the net effect of all biases appears to be an underestimation of average loss. In particular, it is shown that the factor approach can result in an underestimation of average loss of roughly 10–15%. This bias was corrected during a reanalysis of the loss data to reflect new loss totals.

All of this input has resulted in an improved process in which the data were reanalyzed from 1980-2013. This resulted in the identification of 8 new events that after inflation adjustment exceed the one-billion dollar threshold, 9 previously unidentified events, and 2 additional events that occurred in 2013:

New Billion-Dollar (CPI-Adjusted) Events:

  • Southern Severe Storms and Flooding (April 1980)
  • Midwest/Southeast/Northeast Winter Storm/Coldwave (January 1982)
  • Midwest/Plains/Southeast Tornadoes (April 1982)
  • Severe Storms and Hail (June 1984)
  • Western Severe Storms and Flooding (February 1986)
  • Hurricane Lili (October 2002)
  • Midwest/Plains Severe Weather (July 2003)
  • Midwest/Northeast Severe Storms and Flooding (July 2010)

Previously Unidentified Billion-Dollar Events:

  • Southeast Drought (Summer 1983)
  • Florida Freeze (December 1989)
  • U.S. Drought (Spring-Summer 1991)
  • Western/Central Drought/Heatwave (Spring-Fall 2003)
  • Southeast Tornadoes (March 2008)
  • Southern Severe Weather (April 2008)
  • Colorado Severe Weather (July 2009)
  • Ohio Valley/South Tornadoes (April 2011)
  • Midwest/Southeast Severe Weather (August 2011)

New 2013 Billion-Dollar Events:

  • Illinois Flooding and Severe Weather (April 2013)
  • Midwest Severe Weather (August 2013)

It is also known that the uncertainty of loss estimates differ by disaster event type reflecting the quality and completeness of the data sources used in our loss estimation. In 2013, three of the nine billion-dollar events (i.e., the drought and two flooding events) have higher potential uncertainty values around the loss estimates due to less coverage of insured assets. The remaining 6 events (i.e., severe local storms) have lower potential uncertainty surrounding their estimate due to more complete insurance coverage. To that end, we have temporarily rounded our loss estimates to the nearest billion dollars while developing research to define uncertainty and confidence intervals surrounding these estimates.