because of social, political, economic, and technological changes in or affecting coping systems and changes in individuals' abilities to use these systems. The adequacy of estimates of the consequences of future climatic events therefore depends on realistic assessments of these changes in social systems. For example, the expansion of global markets into new regions decreases vulnerability to local droughts for people in those regions who have sufficient resources to buy food in those markets; it may, however, have an opposite effect for low-income people in the same region if it undermines preexisting social norms for sharing with the poor. A new flood-control dam reduces vulnerability to seasonal floods below the dam, and an educational program may get more people to purchase flood insurance.

The effectiveness of coping systems may also change over time. The aftermath of Hurricane Andrew illustrates the phenomenon. In the decades before the hurricane, during which there were few major hurricanes in Florida, major population increases were occurring there, and little attention was being paid to reducing vulnerability through stormresistant building construction techniques. As a result, the disaster insurance industry was not fully prepared, and there were serious disruptions in the cost and availability of coverage for some time afterward. In addition, the building stock in the region was much less hurricane resistant than it might have been.

These changes affect climate sensitivity and the potential value of forecasts. Therefore, efforts to anticipate the effects of climatic events or provide useful forecast information should take into account the possibility that, by the time a climatic event occurs, the target sectors may be in a considerably different situation in terms of vulnerability and of the coping possibilities available than when estimates of climate sensitivity were made.

7.

Successful coping with climatic variations sometimes depends on nonclimatic information. For example, farmers consider crop prices and price forecasts when making planting decisions to hedge against climatic events. Fishers consider information on fish stocks as well as climate forecasts in deciding how intensively to fish. Households and firms consider the price and coverage offered by disaster insurance providers. Such considerations may be obvious to the decision makers, but they may need to be brought to the attention of climate analysts.