The strange red and yellow sky in Edvard Munch's The Scream may have been inspired by a strange cloud formation, researchers say.

The painting by the Norwegian artist Edvard Munch sold for a record $119.9 million in 2012, but the sky in it has been a bone of contention.

Some say it was a volcanic sunset after the 1883 Krakatau eruption, while others think the wavy sky shows a scream from nature.

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Rutgers Professor Alan Robock with an image of The Scream, an 1895 painting by Norwegian artist Edvard Munch. From top to bottom on the right are: a nacreous cloud over McMurdo Station in Antarctica in 2004; an 1883 drawing by William Ascroft showing the sky in London after the Krakatau eruption; and a 1982 volcanic sunset over Lake Mendota in Madison, Wisconsin, after the El Chichón eruption in Chile

WHAT ARE MOTHER-OF-PEARL CLOUDS? Nacreous clouds, sometimes called mother-of-pearl clouds, form in the very cold regions of the lower stratosphere some 15 - 25 km (9 -16 mile) high and well above tropospheric clouds. They are so bright after sunset and before dawn because at those heights they are still sunlit. They are formed when methane in the atmosphere reacts with ozone. Advertisement

Scientists at Rutgers University-New Brunswick, University of Oxford and University of London now believe that nacreous, or 'mother of pearl,' clouds, which are often 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.'

The first version of 'The Scream' was released in 1893.

It depicts a dark human-like figure clutching its head in apparent horror against the backdrop of a swirling, red-orange sky.

Nacreous clouds, sometimes called mother-of-pearl clouds, form in the very cold regions of the lower stratosphere some 15 - 25 km (9 -16 mile) high and well above tropospheric clouds

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.

EDVARD MUNCH'S THE SCREAM 'The Scream' is the popular name given to each of four versions of a composition, created by the Expressionist artist Edvard Munch between 1893 and 1910. The German title Munch gave these works is Der Schrei der Natur (The Scream of Nature). The works show a figure with an agonized expression against a landscape with a swirling orange sky. Edvard Munch created the four versions in various media, including paint and pastel. It is estimated that each composition is worth over £110 million. Advertisement

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.'