London’s sky turns red Monday, but we can’t blame pollution

Residents of England awoke on Monday morning to a sky that looked very much like a scene from the movie Blade Runner—red and hazy. Fortunately this isn't science fiction—or even pollution. Rather, it's a combination of the rare, powerful ex-hurricane Ophelia's winds and African dust.

The large, extra-tropical cyclone that brought high winds and damaging seas to Ireland on Monday also produced a huge swath of powerful southerly winds that brought Saharan dust from the West Coast of Africa all the way north across the Atlantic and Western Europe into the United Kingdom.

The movement of additional dust into the atmosphere scatters blue light from the Sun, giving the sky a more reddish hue, as if it were sunset or sunrise. The strong, southerly winds should abate later Monday or Tuesday as the remnants of Ophelia move quickly to the northeast, away from the United Kingdom.

Saharan dust is much more common across the Atlantic tropics during the summer than the northern latitudes. Pulled toward the Americas by tropical easterlies, the fine particles from Africa often reach areas as far away as Texas and the Amazon River. These dust particles are loaded with phosphorus and provide nutrients important for crops and other vegetation. Outbreaks of Saharan dust also can disrupt tropical storms and hurricanes during the Atlantic hurricane season, as the infusion of drier air chokes off the intensification of a tropical system.

When your cars blend in perfectly with the sky. 🍊 pic.twitter.com/1EKmgDyuGE

— McLaren (@McLarenF1) October 16, 2017

A recent NASA analysis found that wind and weather pick up on average 182 million tons of dust each year from the Sahara Desert and carry it past the western edge of the Sahara at longitude 15°W. This volume is the equivalent of 689,290 semi trucks filled with dust.

Listing image by DANIEL DAN SORABJI/AFP/Getty Images