Bodacious tubes on Australia鈥檚 east coast are being wiped out by global warming. That鈥檚 the finding from research predicting that, at current rates, climate change will crush those big waves. By the end of the century, the number of big waves will have reduced by a third.
The effect of climate change on waves around the globe has been poorly understood because climate models don鈥檛 always accurately predict surface winds, which drive waves.
and his colleagues from the Australian Bureau of Meteorology in Melbourne ran 18 climate models forwards and backwards from the present day to try to spot how the changing climate might influence big waves.
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Looking at data from buoys off the east coast of Australia, they found that big waves were reliably caused by storms in the western Pacific known as 鈥渆ast coast lows鈥�. These storms are themselves driven by differences in air pressure, which climate models predict quite well. The 18 climate models all produced very similar predictions, giving Dowdy a lot of confidence in the results.
Surf鈥檚 down
For waves to be classed as 鈥渂ig鈥� in the model, they had to occur on average no more frequently than about once every 10 days. Averaging across the models, they found climate change is already pushing down the number of big waves and that trend is going to increase.
Where there might have been waves taller than 6 metres on 36 days a year in the 1950s, now it happens on only about 34 days a year. If we continue along a high-emissions path, that will reduce by almost 30 per cent by the end of the century. They found a similar but less dramatic trend for 鈥渕oderate鈥� waves between four and six metres high.
鈥淔ewer large waves may be unwelcome news for some surfers,鈥� says Dowdy. But they might take comfort knowing it鈥檚 still possible that the very biggest waves will get even bigger, he says, something his study didn鈥檛 examine.
Changes in wave height could also have drastic effects on beaches, says from CSIRO, Australia鈥檚 national research organisation in Hobart, who heads-up the . The amount of sand on a beach is determined by the balance between what gets washed in and what gets washed out, and waves are the primary driver of that, he says.
The results can鈥檛 be generalised to other parts of the world, though, Hemer says. The weather conditions that drive waves in this region may not be the same elsewhere so these studies need to be repeated for each location.
Journal reference: Nature Climate Change: DOI: 10.1038/nclimate2142
