John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.
Scientists hope to improve the study of climatology by looking at sunsets in centuries-old landscape portraits.
To study climate change, scientists often must travel to extremely remote places. Clues are stored in fossils on the ocean floor, under the bark of Alaskan trees, and inside air bubbles trapped deep in the Antarctic ice.
Christos Zerefos, an atmospheric researcher at the Academy of Athens in Greece, has a shorter commute. When he wants to investigate the climate, he stares at landscapes executed by some of Britain's most esteemed painters, like this circa-1829 piece by J. M. W. Turner:
Whereas the casual viewer of "The Lake, Petworth: Sunset, Fighting Bucks" might spy a transcendent panorama from one of Romanticism's leading artists, Zerefos notices something different. He sees the sky: a hazy, almost angry-looking blob of dirty-yellow sunlight. To him, the strange colors are evidence that something was happening to alter the atmosphere, and that it was big and violent enough that painters years apart would capture it on their canvases.
After studying hundreds of landscapes made between 1500 and 2000, Zerefos and fellow researchers in Germany believe that these spectacular scenes were the result of volcanic air pollution. More than 80 major eruptions occurred during that 500-year period, they say in a new study in Atmospheric Chemistry and Physics. Some, like the 1815 Tambora explosion in Indonesia, spewed aerosols like ash and sulfates over much of the planet. That created a situation known as high "aerosol optical depth"—basically, there was so much junk floating around that it scattered the sunlight, producing brilliant red-and-orange sunsets that lasted as long as three years after an eruption.
J. M. W. Turner and many other famous painters from yore distilled this air pollution in their masterworks, wittingly or not. The process was universal "regardless of the painters and of the school of painting," reports Zerefos. For the difference a volcano can make on a painting, have a look at Turner's "The Lake, Petworth, Sunset; Sample Study" from 1827 to 1828, a time without a large eruption:
And this is Turner's "Sunset," completed during an active volcanic period in the early 1830s. It's like staring into the fiery interior of a nuclear bomb:
The switching sunsets provide a fascinating bit of trivia for art historians. But Zerefos believes climatologists should take an interest, too. That's because aerosols from volcanic eruptions exert a significant impact on the climate. In just one example, they might play a role in the recent slowdown in global warming. There are written records of eruptions stretching way back, but technology did not exist to log precisely the timing and extent of these sky-cloaking events. The oil-paint-based method of deduction provides one more way of studying the history of aerosols, according to the research team:
Since aerosols scatter sunlight, less of it reaches the surface, leading to cooling. The Tambora eruption, the largest in recorded history, killed some 10,000 people directly and over 60,000 more due to the starvation and disease during the 'volcanic winter' that followed. Aerosol optical depth can be directly used in climate models, so having estimates for this parameter helps researchers understand how aerosols have affected the Earth's climate in the past. This, in turn, can help improve predictions of future climate change.
To show that it's not just crusty 19th-century painters who were vulnerable to the sunset effect, Zerefos and company performed one more experiment. They asked Greek post-impressionist Panayiotis Tetsis to paint scenes of the island of Hydra both during and after another significant aerosols event: a Saharan dust cloud that passed over Europe in 2010. Here's the gold-beaming sun while the airborne-particle storm was ongoing, followed by a contemporaneous photo:
And this is the sky after African dust had exited the region. It's a much calmer-looking vista over the Aegean Sea:
Top image: "The Lake, Petworth: Sunset, Fighting Bucks," by J. M. W. Turner, circa 1829. Bottom: digitally compressed paintings by P. Tetsis, photos by C. Zerefos.