PLANNING FOR SEA-LEVEL RISE AND SHORE PROTECTION UNDER CLIMATE UNCERTAINTY

Attention is focused here on the effect of additional sources of uncer tainty derived from climate change on the cost-benefit procedures appl ied by coastal planners to evaluate shoreline protection projects. The largest effect would be felt if planners were trying to achieve the f irst best economic optimum. Given the current view that the seas will rise by significantly less than one meter through the year 2100, prese nt procedures should work reasonably well assuming (1) informed vigila nce in monitoring the pace of future greenhouse induced sea level rise , (2) careful attention to the time required for market-based adaptati on to minimize the economic cost of abandonment, and (3) firm support of the credibility of an announced policy to proceed with plans to ret reat from the sea when warranted. Assumptions (1) and (2) might be sat isfied in reality, even cursory review of existing policy makes it cle ar that meeting (3) is a ''long shot'' at the very best. In any case, planners should periodically revisit potential protection sites, espec ially in the wake of catastrophic events, to assess the impact of the most recent information on sea level rise trajectories, local developm ent patterns, and protection costs on the decision calculus.