Scientists use Van Gogh's sunsets to understand climate

Vincent Van Gogh's Sunset at Montmajour may be your favourite painting for its sublime and serene use of colours but for a group of Greek and German scientists it may provide vital clues about how the Earth's atmosphere was when Van Gogh painted it.  Their article is published in Atmospheric Chemistry and Physics.

According to the scientists, analysing the colors of the sunsets in paintings can give an idea of the level of ash, gas, and other pollutants that may have been present in the atmosphere at that time. Particularly, following major volcanic eruptions, painters may have seen darker evening skies as the ash and gas released during the eruptions scatter the different colours of sunlight, making sunsets appear redder.

In 1815, Mount Tambora erupted in Indonesia. It was the largest volcanic eruption in recorded history and heavy volcanic ash falls were observed in faraway places. The ash and gas from the eruption was spewed into the atmosphere and travelled all over the world, causing global climate anomaly. The aerosol particles scattered the sunlight and many parts of the world experienced bright red and orange sunsets. Europe saw these sunsets for up to three years after the eruption. J. M. W. Turner was one of the artists who painted the stunning sunsets during that time. His The Lake, Petworth: Sunset, Fighting Bucks was one of the paintings to be analysed by the scientists to determine the composition of the atmosphere following the eruption.

"Nature speaks to the hearts and souls of great artists," says lead-author Christos Zerefos, a professor of atmospheric physics at the Academy of Athens, Greece. "But we have found that, when colouring sunsets, it is the way their brains perceive greens and reds that contains important environmental information."

The scientists also analysed hundreds of high-quality digital photographs of sunset paintings created between 1500 and 2000. This period has recorded over 50 large volcanic eruptions around the globe. They were looking to find out whether the relative amounts of red and green along the horizon of each painting could provide information on the amount of aerosols in the atmosphere.

"We found that red-to-green ratios measured in the sunsets of paintings by great masters correlate well with the amount of volcanic aerosols in the atmosphere, regardless of the painters and of the school of painting," says Zerefos.


Skies more polluted by volcanic ash, mineral (desert dust), or man-made aerosols appear more red since these tiny particles scatter more sunlight. Air with a higher amount of aerosols has a higher 'aerosol optical depth'. The team calculated this parameter using the red-to green ratios in the paintings. They then compared these values with those given by independent proxies such as ice-core and volcanic-explosivity data that measure the amount of material ejected by a volcano, and found that they matched. The results obtained validate those of the team's previous study, published in Atmospheric Chemistry and Physics in 2007. 

The scientists wanted to further validate their findings by observing a dust cloud through the eyes of a painter so they asked a famous colorist to paint sunsets during and after the passage of a Saharan dust cloud over the island of Hydra in June 2010. The scientists then compared measurements of the aerosol optical depth made by modern instruments with those that emerged from the red-to green ratios in the painting and other digital pictures and found that they matched well.The after effects of the Tambora volcano were devastating with human death toll reaching 70,000 of which 10,000 were killed directly by the eruption. The other deaths were caused due to famine and diseases that resulted due to the 'volcanic winter' that followed the eruption.

Aerosol optical depth can be directly used in climate models to determine how aerosols have affected the Earth's climate in the past. Similarly, they can be used to improve predictions of future climate change."We wanted to provide alternative ways of exploiting the environmental information in the past atmosphere in places where, and in centuries when, instrumental measurements were not available," concludes Zerefos.

International Science Times