The increase in the concentration of atmospheric greenhouse gas will reduce the number of days with large ocean waves of more than four metres in height for eastern Australia, reports a paper published online in Nature Climate Change. This research could help in better understanding and predicting elevated water levels or coastal erosion in the region.
Large ocean waves in the mid-latitude regions are predominately caused by strong winds associated with extratropical cyclones. Andrew Dowdy and colleagues use observations from 1992-2010 to analyse storm days and associated wave events of four different heights: 2 metres or smaller, 2-4 metres, 4-6 metres and 6 metres or larger. They built a diagnostic model to evaluate the risk of large wave occurrences for various atmospheric pressure conditions in the upper-troposphere - as would be experienced during extratropical cyclone events - in eastern Australia. This approach was then applied to projections for this region from 18 different global climate models. Dowdy and colleagues report that for an intermediate level of greenhouse gas emissions there will be 25% fewer storm wave events, and for high emission levels there will be 42% fewer storm wave events for the 2070-2100 period compared with the historical average.
The authors note that the new method used in this study results in highly consistent results between the different climate models.