Could a greener world be bad news for green energy? Wind speeds are falling across much of the northern hemisphere, and this could mean less electricity is available from wind turbines. An increase in the amount of vegetation may be to blame.

Which one will catch the wind? (Image: John Kelly/Getty)

Robert Vautard at the Laboratory of Climate and Environmental Sciences (LSCE) in Gif-sur-Yvette, France, and colleagues analysed surface wind speed data from 822 sites around the world, covering the last 30 years.

They found that surface wind speeds have declined by 5 to 15 per cent across much of the northern hemisphere over this period. The slowing has been more marked for winds of over 10 metres per second than for lighter winds.

When Vautard and his team modelled the effect of vegetation increases across Europe and Asia over the period, they found this could explain most of the drop-off. "Large parts of Earth are becoming greener, partly due to efforts in Europe to maintain forests," says Jean-Noel Thépaut of the European Centre for Medium-Range Weather Forecasts in Reading, UK, who took part in the research.

Power loss

Wind turbines operate most efficiently when winds are stronger, so a continuing decline in the highest surface wind speeds would lead to a significant drop in wind power production, the researchers say.

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