WeatherZine WeatherZine Number 12, October 1998
"What's happening on the Societal Aspects of Weather WWW Site."


EditorialAn Optimal Number of Disasters?

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An Optimal Number of Disasters?

Conventional wisdom suggests that more disasters means more costs to society, but this view neglects learning through experience. To provoke your thinking, here I offer an alternative view.

Consider the following two recent events: First, in the aftermath of Hurricane Andrew (1992) one of the lessons learned was that homeowners, insurers, and many others we caught unprepared because it had been so long since the area had been hit by such a powerful storm. Some estimate that many billions of dollars in damages might have been averted with only a small up front investment. Second, in the North Dakota Floods of 1997, Fargo, North Dakota responded effectively to the flood and avoided major damages. Some in the community claim that one important reason for this was that they fight floods on a regular basis, and are thus well prepared for even extreme events. These two cases, and many like them, suggest a broader lesson about disasters:

Given that a community experiences disasters (more precisely, hazardous events whether floods, hurricanes, earthquakes, etc.), over the long term there is an optimal number of disasters at which the community will experience the lowest societal costs (if of course, they are able to incorporate the lessons of experience).

In other words, if disasters occur too infrequently, the community will become complacent, let preparation atrophy, and face difficulties in addressing issues of long-term mitigation. If disasters occur too frequently, or a community is unable to incorporate the lessons of experience, then the community would likely be overwhelmed by the cumulative costs of the events. Perhaps somewhere in between lies a point where the community gets enough "practice" with disasters to learn how to deal with them effectively, but does not become overwhelmed by their effects. This relationship is shown graphically in the accompanying figure, along with a conventional view of the relationship of disasters and costs (not to scale).

Long Term Societal Costs vs Frequency of Disasters

There are a number of reasons why such a relation might not exist. One is that the costs of a "disaster" are simply so large that the beneficial effects of learning over time, while significant, might not be able to compensate for the absolute costs of the event. For instance, Hurricane Andrew cost more than $30 billion. If we could have saved $10 billion, then it still would have been, by far the most costly hurricane of all time (in absolute terms). So perhaps such a relationship exists for disasters other than the most catastrophic.

Another reason is that some events may occur with such infrequency that learning is difficult to incorporate into decision making. For instance, some places experience earthquakes only once every few decades. So perhaps the relationship exists only for events that occur with sufficient frequency so as to allow for effective learning by decision makers.

But this leaves an fairly large subset of disasters (and communities) for which such a relationship might exist. And while different communities would likely show a different "curve" for contextual reasons like culture, history, environment, etc., knowledge of the existence of such a relationship would have important policy implications. For instance, if we could identify where a particular community lies on the curve, then there are implications for policy:

For communities with a lower frequency of disasters than is optimal, then the disaster planners might want to focus disaster mitigation efforts on education and awareness.

For communities with a higher frequency of disasters than is optimal, the disaster planners might want to focus their efforts on structural mitigation, relocation, and disaster assistance.

For communities with an optimal frequency of disasters, then disaster planners might want to draw lessons from the community's response and seek to disseminate them elsewhere.

Finally, the existence of such a relationship raises the possibility that mitigation efforts might be more closely tied to reliable predictions about future incidence of hazardous events.

Of course, the relationship of disasters and costs is much more complex than can be shown in a simple graph, and the overall frequency of disasters might be neither sufficient nor necessary to lead to lower costs. Nonetheless, we have enough experience with disasters to test such a relationship and its implications. Because we live in a world where experiential knowledge is so important, knowing if such a relationship exists would seem to be an important factor in understanding how society responds to disasters.

— Roger A. Pielke, Jr.

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Community News

Weather Journal Articles and Info Online

The American Meteorological Society has provided a number of services to the community worth your attention.

The full text of the journals of the American Meteorological Society are available online at The journals that include articles related to the societal impacts of weather include the following:

Journal of Applied Meteorology. Applied research related to the physical meteorology, cloud physics, hydrology, weather modification, satellite meteorology, boundary layer processes, air pollution meteorology (including dispersion and chemical processes), agricultural and forest meteorology, and applied meteorological numerical models of all types.

Weather and Forecasting. Articles on forecasting and analysis techniques, forecast verification studies, and case studies useful to forecasters. In addition, submissions that report on changes to the suite of operational numerical models and post-processing techniques, and articles that demonstrate the transfer of research results to the forecasting community.

Journal of Climate Articles on climate research and, therefore, welcomes manuscripts concerned with large-scale atmospheric and oceanic variability, changes in the climate system (including those caused by human activities), and climate simulation and prediction.

Bulletin of the American Meteorological Society . The official organ of the society, devoted to editorials, topical reports to members, articles, professional and membership news, conference announcements, programs and summaries, book reviews, and society activities.

Earth Interactions. Publishes in the electronic medium original research in the earth system sciences with the emphasis on interdisciplinary studies. Within framework, the journal particularly encourages submissions that deal with interactions among lithosphere, atmosphere, and biosphere in the context of global issues or global change.

If your are interested in searching the meteorological and geophysical literature then you will be interested in Meteorological and Geophysical Abstracts online at, a valuable site which allows you to search the voluminous literature in this area.

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