Billion-Dollar Weather and Climate Disasters: Overview

Hurricane Katrina

The National Centers for Environmental Information (NCEI) is the Nation's Scorekeeper in terms of addressing severe weather and climate events in their historical perspective. As part of its responsibility of monitoring and assessing the climate, NCEI tracks and evaluates climate events in the U.S. and globally that have great economic and societal impacts. NCEI is frequently called upon to provide summaries of global and U.S. temperature and precipitation trends, extremes, and comparisons in their historical perspective. Found here are the weather and climate events that have had the greatest economic impact from 1980 to 2015. The U.S. has sustained 188 weather and climate disasters since 1980 where overall damages/costs reached or exceeded $1 billion (including CPI adjustment to 2015). The total cost of these 188 events exceeds $1 trillion.

2015 in Context

In 2015, there were 10 weather and climate disaster events with losses exceeding $1 billion each across the United States. These events included a drought event, 2 flooding events, 5 severe storm events, a wildfire event, and a winter storm event. Overall, these events resulted in the deaths of 155 people and had significant economic effects on the areas impacted. The 1980–2015 annual average is 5.2 events (CPI-adjusted); the annual average for the most recent 5 years (2011–2015) is 10.8 events (CPI-adjusted). Further cost figures on individual events in 2015 will be updated when data are finalized.

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Additionally, the U.S. experienced five distinct disaster event types in 2015. It is more common to observe three or four disaster event types in a given year. Five or more disaster event types exceeding $1 billion in the same year occurs less frequently (i.e., 2015, 2011, 2008, 1998, 1994 and 1989).

Methodology and Data Sources

In 2012, NCEI -- then known as National Climatic Data Center (NCDC) -- reviewed its methodology on how it develops Billion-dollar Disasters. NCEI held a workshop with economic experts (May, 2012) and worked with a consulting partner to examine possible inaccuracy and biases in the data sources and methodology used in developing the loss assessments (mid-2013). This ensures more consistency with the numbers NCEI provides on a yearly basis and give more confidence in the year-to-year comparison of information. Another outcome is a published peer-reviewed article "U.S. Billion-dollar Weather and Climate Disasters: Data Sources, Trends, Accuracy and Biases" (Smith and Katz, 2013). This research 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 approximately 10–15%. This bias was corrected during a reanalysis of the loss data to reflect new loss totals.

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 2014, two of the eight billion-dollar events (i.e., the drought and flooding event) have higher potential uncertainty values around the loss estimates due to less coverage of insured assets. The remaining 6 events (i.e., 5 severe local storms and a winter storm) 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 implementing our newest research to define uncertainty and confidence intervals surrounding these loss estimates. The peer-reviewed article "Quantifying Uncertainty and Variable Sensitivity within the U.S. Billion-dollar Weather and Climate Disaster Cost Estimates" (Smith and Matthews, 2015) is a next step to enhance the value and usability of estimated disaster costs given data limitations and inherent complexities.

In performing these disaster cost assessments these statistics were taken from a wide variety of sources and represent, to the best of our ability, the estimated total costs of these events -- that is, the costs in terms of dollars that would not have been incurred had the event not taken place. Insured and uninsured losses are included in damage estimates. Sources include the National Weather Service, the Federal Emergency Management Agency, U.S. Department of Agriculture, other U.S. government agencies, individual state emergency management agencies, state and regional climate centers, media reports, and insurance industry estimates.

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