The Scream: What were those colorful, wavy clouds in Edvard Munch's famous painting?

But scientists at Rutgers University-New Brunswick, University of Oxford and University of London suggest that nacreous, or "mother of pearl," clouds which can be seen in southern Norway inspired the dramatic scene in the painting. Their study is published in the Bulletin of the American Meteorological Society.

"What's screaming is the sky and the person in the painting is putting his or her hands over their ears so they can't hear the scream," said Alan Robock, study co-author and distinguished professor in the Department of Environmental Sciences at Rutgers-New Brunswick. "If you read what Munch wrote, the sky was screaming blood and fire."

There are four known versions of The Scream: an 1893 tempera on cardboard; an 1893 crayon on cardboard; an 1895 pastel on cardboard that billionaire Leon Black bought for nearly $120 million at auction; and a tempera on hard cardboard thought to have been painted in 1910.

Iridescent light from below the horizon illuminates polar stratospheric clouds, also known as nacreous clouds. Robock said the sky colors and patterns in Munch's paintings match sunset colors better when nacreous clouds are present versus other scenarios.

The study builds on a 2017 study that also proposed nacreous clouds. The new study provides a more detailed and scientific analysis of Munch's paintings, focusing on photographs of volcanic sunsets and nacreous clouds and analyzing the color content and cloud patterns. If the new analysis is correct, Munch's art is one of the earliest visual documentations of nacreous clouds, the study says.

Robock and others have previously proposed that a volcanic sunset inspired the painting, and he still thinks that's possible.

"We don't know if Munch painted exactly what he saw," Robock said. "He could have been influenced by the Krakatau sunset and nacreous clouds and combined them."