Researchers paint a picture of volcanology

Scientists have resorted to an unusual source of evidence to trace the history of volcanic eruptions on Earth and their effect on the climate - by studying paintings.

The effects of historical eruptions on the composition of the atmosphere are difficult to estimate owing to a lack of measurements or samples surviving from those times. 

Now, Christos Zerefos, from the Academy of Athens in Greece, and his colleagues have come up with a proxy measure that could be used to shed light on the problem - old masterpieces. 

They analysed the sunsets immortalised in hundreds of paintings from the last 500 years, including works by Turner, Klimt and Degas. 

Using digital images of the paintings, the team calculated the ratios of red to green colours and found that artists used much more red after major volcanic eruptions, such as the explosions at Krakatoa in 1883 and 1680.

Next, using the red-green ratios from the paintings, the team were able to calculate how much light was being interrupted by volcanic ash particles in the air. 

Their results tally well with what we know of the composition of the atmosphere at these times, suggesting that this could be  an effective way to historically reconstruct the stratosphere.