Understanding climate-driven impacts on the global wind-wave climate is critical to effective planning for offshore/coastal climate adaptation. This week, an international team of researchers under the auspices of the global COWCLIP (Coordinated Ocean Wave Climate Projections) Project – in which IHE Delft is a partner – has published new research mapping the impact of climate change on future wave climate around the globe.
The study, “Robustness and uncertainties in global multivariate wind-wave climate projections”, published in Nature Climate Change, provides a comprehensive assessment of existing community-driven, multi-method global wave climate projections. Drawing on the expertise of 10 international research groups, it concludes that, if the 2° C Paris Agreement target is achieved, signals of wave climate change are unlikely to exceed those of natural climate variability. However, under a business-as-usual emission scenario, there are consistent changes predicted for the wave heights, lengths and/or directions along 50% of the world’s coasts.
Alvaro Semedo, from IHE Delft’s Coastal Engineering and Port Development group, and one of the paper’s lead authors, explains that the predictions reveal around 5% of the global coastline that is at serious risk of future increasing wave heights: the southern coasts of Australia, and segments of the Pacific coast of South and Central America. But, he adds, predicted increases in wave heights and/or duration would lead to increased stress on coasts and coastal infrastructures.
The work combines a range of statistical and dynamical wave models with outputs from several global climate models, and under different future greenhouse gas emission scenarios, to determine how future wave climate might behave. By comparing projections for 2081 to 2100 with present-day climate, the group predicts significant potential impacts under a range of high-emission scenarios – including increased wave height and duration, and shifts in wave direction, each to the order of up to 5-15%. It also reveals strong agreement amongst wave climate projections for approximately 50% of the world’s coastline, with about 40% showing robust changes in at least two of the key variables (wave height, duration, or mean direction).
This extensive collection of wave climate projections also showed that uncertainty is dominated by climate model-driven uncertainties, and that single-method modelling studies are unable to capture up to ~50% of the total associated uncertainty.