Hard data on the annual rise and fall of Earth’s global surface temperatures only goes back about 150 years. Before then, there were few instruments available to monitor changes in the planet’s atmosphere. To get an idea of what the skies were like before the 20th century, scientists are getting help from an unlikely source: 18th- and 19th-century landscape paintings.
Researchers from the Academy of Athens say that landscape paintings by old masters like J.M.W. Turner can give them an idea of what the skies were like before the days of recordkeeping. Turner’s work, in particular, which often depicts brightly colored sunsets and emphasized natural light, can be used to roughly estimate aerosol optical depth – that is, the amount of particles like dust, volcanic ash, smoke and sea salts in the atmosphere – at the time the painting was made.
The study, published in the journal Atmospheric Chemistry and Physics, says scientists can determine with some certainty the levels of particulates in the air at the time the landscape paintings were made based on the color of the sunsets. They say that artists’ sunsets have increasingly gotten redder over the past 150 years, which could suggests the painters were seeing more manmade and natural particulates in the air.
"Paintings may provide reliable estimates on aerosols in the atmosphere at times before instrumental measurements," Christos Zerefos, professor of atmospheric physics at the Academy of Athens in Greece and lead author of the study, told The Daily Climate.
For example, for a three-year period following the 1815 Tambora volcano eruption in Indonesia, European artists painted skies that were bright red and orange. The reason, according to researchers, was that volcanic ash and gas spewed into the atmosphere had traveled around the world and scattered sunlight, producing new shades of color in the sky.
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“Nature speaks to the hearts and souls of great artists,” Zerefos said in a statement, according to The Telegraph. “But we have found that, when coloring sunsets, it is the way their brains perceive greens and reds that contains important environmental information.”
Researchers studied 124 sunsets by European artists painted between 1500 and 2000. Fifty large volcanic eruptions occurred around the world during that period. Zerefos said that reds and greens found in the paintings correlated well with the amount of volcanic ash and dust in the atmosphere.
Scientists also found that sunsets were redder from the Industrial Revolution onward, even when there were no volcanic eruptions.
"Aerosols have influenced Earth's temperature records,” A.R. Ravishankara, professor of chemistry and atmospheric science at Colorado State University who was not involved in the study, told Scientific American. “By correlating colors in paintings with aerosol optical depth, this study helps to validate historical temperature reconstructions.”