Towards reliable global allowances for sea level rise

Tide gauge data and information from tide, surge and ocean models have been used to calculate and validate the Gumbel scale parameters of extreme sea level distributions along the world coastline. The inclusion of ocean model information is found to result in significantly improved correspondence between observed and modelled scale parameters to that obtained using tide and surge model information alone. The scale parameters so obtained are shown to be consistent with findings reported previously, such as in assessments of the Intergovernmental Panel on Climate Change. However, the considerably improved provision of scale parameters along the coast means that coastal planners, and others concerned with impacts of sea level rise, can now undertake more complete investigations of the likely increase in sea level exceedance frequencies. In addition, coastal engineers will have access to more reliable estimates of the ‘sea level allowances’ needed to design defences for protecting coastal populations.