Projection of tropical cyclone-generated extreme wave climate based on CMIP5 multi-model ensemble in the Western North Pacific

Climate change impacts on future ocean wave climate have been studied using a suite of Global Climate Models (GCM). We investigated the representation of extreme (annual maximum) wave climate in the Atmosphere-Ocean GCM (AOGCM) driven wave climate projections, specifically looking at tropical cyclone (TC)-generated extreme waves in the Western North Pacific. The representation of the extreme wave climate by AOGCM driven wave climate projections was evaluated by comparing with higher-resolution AGCM driven wave climate projections, reanalysis and observations. We find better performance of AOGCM's to simulate TCs leads to significantly improved representation of the extreme wave climate. The better performing models can produce more than 30 ms(-1) wind speed in TCs and the frequency of occurrence of TCs is 80 % of the observed frequency of occurrence. The projected changes in the extreme wave climate are dominated by changes in TC-generated waves. Although the projected changes in TC-generated wave heights show the coherent decreases in some models with greater TC skill, there is a large variation in the projected changes among models. The other models which are less able to resolve the TC characteristics display projected changes dominated by non-TC generated waves systems, which is the decrease in wave heights around latitudes 30 degrees N. Although there is a large variation in the projected changes in TC-generated waves, the change ratio is 2 times larger than those of non-TC waves. Therefore, appropriate interpretation of the TC-generated wave changes and its variation is important for risk assessment.