Between 1500 and 2000, the world saw more than 50 major volcanic eruptions. Each such eruption releases very fine particles into the air, like ashes, dust and other pollutants, which mix with the air and its moisture to form a mixture called an aerosol.

Aerosols can remain suspended in the atmosphere for long periods of time, and affect the quality of sunlight reaching the ground below. So, it is important for scientists to know how they affect the atmosphere so that they can tackle the air pollution today better.

A team of Greek and German researchers has taken a little-travelled route to study the effect of these volcanic eruptions in the last five centuries: they studied paintings.

“Nature speaks to the hearts and souls of great artists,” said Christos Zerefos, from the Academy of Athens in Greece. Prof. Zerefos & co. studied how different painters had painted sunsets.

In particular, they analysed how they used red colour. A sky that contains aerosols appears reddish because the fine particles in the aerosols scatter sunlight in different directions. So, light of the longer wavelength reaches the ground. Since the colour red has the longest wavelength, a brightly lit sky at sunset appears more red.

Using the amount of red in the paintings, scientists calculated the amount of aerosols in the air that could have originated from volcanoes. They compared their results to those obtained from volcanic explosions data, and found good agreement. Their findings were published in the journal Atmospheric Chemistry and Physics on March 25.

Their work proves useful to study climate change also because, since aerosols scatter sunlight, they also reduce the amount of heat reaching the ground. This causes cooling. So, this work also shows a new way to see how Earth’s climate evolved in the last 500 years as its atmosphere changed.