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actors to use their coping systems differently in order to improve their outcomes relative to what they would have been without the forecast.

Estimating the Effects of Climate Variations

An effect of climatic variations in a particular time period for a particular actor, activity, or region can be defined as the difference between an outcome for that period and the long-term average of similar outcomes, net of nonclimatic influences and of longer-term changes in average climate. According to this definition, each region or activity has climate-induced good and bad years, compared with long-term averages.

Using this definition to measure the effects of climatic variations is not a simple matter. It requires first that the effects of climatic variability on a range of outcomes be identified and measured for each sensitive activity in each region. Monetary effects and deaths and serious injuries from extreme weather events are relatively easy to identify and measure, but many other effects are not. For extreme events, they include uninsured injuries and property losses, as well as other effects that are harder to quantify, such as increased community cohesion in the immediate period of disaster recovery and in the longer term, community recognization and shifts in employment patterns, with some people benefiting and others losing.

The effects of nonextreme climatic variations can be particularly difficult to measure. Although many extreme negative events are routinely tallied, few nonextreme events are. The effects of such climatic variations are often subtle or distant in time from their causes, and, for these reasons, causality may be hard to establish. Some effects are deleterious and others are beneficial. It is necessary to model many of these effects rather than measuring them directly, as can be done with storm damage. Econometric models have been used in attempts to value commonplace weather events (e.g., Center for Environmental Assessment Services, 1980), but with mixed success.

Estimating the effects of climatic variation requires that data be developed on the various outcome variables and on things that may affect them, both in the time periods of interest and over a long enough past to establish historical averages. In any weather-sensitive sector, many outcome variables may be affected by climatic variability either directly or indirectly. In agriculture, for example, weather-sensitive outcomes include not only crop yields and income from crop sales, but also the costs (in money and time) of crop selection, water management, crop hazard insurance, participation in the futures market, government disaster payments, and so forth. Each of these activities may be affected by climatic



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