Uncertainties of Climate Modeling and Effects on Wave Induced Bending Moment

Ocean going ships are exposed to the environmental forces from waves and wind and the expected environmental loads over the life cycle of the ship need to be taken into account in the design. Classification societies have, by gathering historical observations of met-ocean conditions, developed rules based on semi-analytical models for response and strength, empirically modified to obtain agreement with observations. The safety level of existing ship structures is thus, to a large extent, defined by failure statistics and proven by successful operational experience. The fundamental assumption behind this practice is that observed data are stationary and ergodic. Because of climate change this no longer holds, however, and within a climate change perspective, the historic data will not represent a valid met-ocean description of future conditions. Therefore, the effect of climate change needs to be considered in ship design and operations. Even though there is general agreement among the majority of the world’s leading climate scientists that the world is experiencing climate change, there are still large uncertainties related to any climate projections and this uncertainty must also be taken into consideration. In this paper, the potential effect of climate change on the ocean wave climate is investigated and the possible impacts on safety of ships are demonstrated using the wave induced bending moment as an example. In particular, projections of the wave climate for a location in the North Atlantic Ocean will be analyzed and related uncertainties will be presented. The results will be discussed in the perspective of a risk-based framework for climate change adaptation, which is adopted in order to evaluate different design options.