A plume of Sahara dust that has blanketed parts of southern and central Europe in recent days caused a short, sharp spike in air pollution across the region, researchers said Tuesday.

The European Commission's Copernicus satellite monitoring program said measured levels of particles smaller than 10 micrometers, so-called PM10s, increased in places such as Barcelona, Spain and in the French cities of Lyon and Marseille on Sunday.

The cloud of fine sand blown northward from Algeria tinted skies red and mixed with fresh snowfall in the Alps and Pyrenees, leaving slopes looking orange.

While PM10 particles can enter the lungs, causing breathing difficulties, asthma attacks and other health problems, the concentration of Sahara dust didn't reach levels considered harmful.

More than three years ago, Storm Ophelia turned skies a spooky shade of sepia across parts of Britain.

That storm brought dust from the Sahara and smoke from wildfires in southern Europe. Ophelia caused two deaths in Ireland, where it was the worst storm in half a century. Social media users shared photos of ominous clouds blocking out the sun, prompting the Science Museum in London to joke on Twitter: "It's not the apocalypse!"

Many people expressed concern about this phenomenon, while others have noted that it looks like something from a science fiction movie.