Global sea-level rise and equity weighting

Using the FUND model, an impact assessment is conducted over the 21st century for rises in sea level of up to 2-m/century and a range of national socio-economic scenarios. This model balances the costs of retreat with the costs of protection, including the effects of coastal squeeze. While the costs of sea-level rise increase due to greater damage and protection costs, the model suggests that an optimum response in a benefit-cost sense remains widespread protection of developed coastal areas, as identified in earlier analyses. The socio-economic scenarios are also important in terms of influencing these costs. In terms of the four components of costs considered in FUND, protection seems to dominate, with substantial costs from wetland loss under some scenarios. The regional distribution of costs shows that a few regions experience most of the costs, especially East Asia, North America, Europe and South Asia. Importantly, this analysis suggests that protection is much more likely and rational than is widely assumed, even with a large rise in sea level. However, there are some important limitations to the analysis, which collectively suggest that protection may not be as widespread as suggested in the FUND analysis. Equity weighting allows the damages to be modified to reflect the wealth of those impacted by sea-level rise. Taking these distributional issues into account increases damage estimates by a factor of three, reflecting that the coasts fall disproportionately on poorer developing countries. 1 Corresponding author. Email: david@anthoff.de, postal address: FNU – ZMK, Bundesstr. 55, 20149 Hamburg, Germany.