Simulations of the response of the ocean waves in the North Atlantic and North Sea to CO2 doubling in the Atmosphere.

Data from high resolution numerical experiments are analysed to study the effect of greenhouse warming on the atmospeheric climatology of the North Atlantic region. By comparing data from a control experiment with analysis data, it is shown that the climate model simulates a fairly realistic current climate. A 2×CO2 experiment is compared with the control experiment. In this comparison, the mean sea level pressure, the near surface winds and the variability of the 500 hPa geopotential heights are considered. The spatial distribution and frequency of the storms over the North Atlantic are also studied. Small regional differences are detected. In particular, there is an increase in the frequency of winds from the northwesterly direction. However, these effects are small compared to the magnitude of the low frequency natural variability in the North Atlantic area. It is therefore not possible to say whether they are caused by external forcing.
Near-surface winds from two climate model data sets were used to drive an ocean wave model, WAM, in order to determine the sensitivity of the wave climatology to the small differences seen in the climatology of the winds. The average wave heights, the variability of the wave heights and the extreme wave heights of the two simulations were compared. Further analysis of the extreme wave heights is done using statistical techniques. Small local differences are detected which reflect the differences in the wind fields from the climate model experiments, although their relative magnitude is generally smaller than that of the anomalies in the winds.