85th AMS Annual Meeting

Monday, 10 January 2005: 4:00 PM
Uncertainties in estimating the impacts of complex climatic events: Revisiting the case(s) of drought
Russell Bigley, NOAA/ERL/CDC, Boulder, CO; and R. S. Pulwarty and M. J. Hayes
Uncertainties in estimating the impacts of complex climatic events: Revisiting the case(s) of drought

Roger S. Pulwarty, Russell Bigley* NOAA/CIRES/Climate Diagnostics Center Boulder CO. Michael Hayes, National Drought Mitigation Center Lincoln Nebraska *corresponding author

Science can reinforce the healthy aspects of the politics of policy processes which identify and further the common interest by helping to select among 'science-confident' and 'hedging' options for pro-active management. In the context of climate variability and change, scientists must learn how to understand, manage and communicate the degrees of uncertainty in knowledge and prediction both of events and of their associated impacts. The alternative is for uncertainty to be manipulated to discredit science or to justify inaction. An area of climate-society interactions fraught with uncertainties is also one in which, given millennia of experience, it is easier to assume that we know more than we do. This is the area of loss estimations associated with drought impacts. Drought occurs every year across different regions within the U.S. The average area affected by severe and extreme drought each year is 14%. The area affected has been as high as 65% (1934) and has hovered in the 35-40% range in recent years. FEMA (1995) estimates that drought results in average losses of $6-8 billion each year. How such numbers are arrived at is unclear, even at the level of the state. Available economic estimates of the impacts of drought are difficult to reproduce and are likely to be either higher or lower for any given year. Problems in estimating drought impacts are confounded by the following: The nature of drought. Drought is slow in its onset and impacts tend to vary in location and scale Scale. Impacts are both direct and indirect. Secondary impacts may be larger than for other climatic extremes Aggregation. Over larger regions (such as for national estimates) drought impacts average out due to 'winners' and 'losers' of local impacts, mitigation practices, and inter-regional markets Collinearity. Some impacts may be counted twice due to the widespread nature of drought (affecting more than one industry) Duration of impacts. Cumulative impacts of drought may extend beyond the period of its climatological duration or over multiple seasons especially in local areas Data availability and quality. There is no central clearinghouse for impacts data concerning drought Selected sites are used to illustrate these issues.

While multi-billion dollar estimates for annual agricultural losses exist (averaging about $4b a year over the last ten years), it is unclear whether these losses are directly related to crop production alone or other factors. Little or no official loss estimates exist for the energy, recreation/tourism, timber, livestock, or environmental sectors, although the drought impacts within these sectors in recent years has been known to be large. Other loss estimates about which little information exists are municipal system losses and indirect costs associated with wildfire suppression. Municipal losses are based on voluntary and mandatory water use restrictions. Wildfire suppression costs to the USDA alone have surpassed $1 billion each of the last 4 years. It is imperative that future drought management efforts, and climate impacts assessments in general, recognize the unique nature of drought, its natural and social dimensions, and the difficulties of developing effective cost estimates of impacts as inputs to evaluating mitigation strategies.

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