12 June 2007, NewScientist.com news service

Gigantic ocean waves, spanning hundreds of kilometres from crest to crest, have been speeding up thanks to global warming, a new model suggests.

Geophysicists predict that as the ocean surface warms, these so-called planetary waves should speed up. To test this idea, John Fyfe and Oleg Saenko at the University of Victoria in British Columbia, Canada, modelled the changes to ocean wave patterns over the 20th and 21st centuries.

"We were really surprised at how quickly the ocean responded to temperature change," Fyfe says. According to the model, global warming has already increased the speed of the waves, but no one noticed because satellites have not been monitoring their speeds for long enough, he says. The model also shows that by the end of the 21st century, the waves will be a further 20 to 40 per cent faster compared with pre-industrial speeds (Geophysical Research Letters, vol 34, p L10706).

"We knew we'd see an effect, but we didn't think it would be significant for at least another two centuries," Fyfe says. The faster planetary waves will have an effect on global weather, he adds.