Weatherwatch: global wind speeds weakening over land

Across the world’s land masses, measured wind speeds have been mysteriously weakening for the past 50 or so years, in some regions slowing down by as much as 25%. Several studies have come to the same conclusion, using wind observations from weather stations across the world.

Strangely, the slowdown seems to be happening largely over land. Over the oceans the phenomenon is less pronounced, with some areas even showing an acceleration. One suggestion is that climate change is partly to blame by altering patterns in the global atmospheric circulation. Another suggestion is that urban development and more vegetation is creating a rougher ground surface that slows winds. However, winds have slowed down across Saudi Arabia, mostly desert, which probably means this is only part of the answer. Now an EU-funded project is trawling through historical records back to the 1880s to find out whether this phenomenon is part of a much longer climate cycle.

Whatever the cause, the slowdown is worrying. Slower winds can affect plant growth and also make it more difficult for air pollution in big cities to dissipate. Wind turbines may also be affected but it is not clear whether this “stilling” is confined to surface winds or whether it reaches up to turbine height.