Can an art museum provide clues to pollution 200 years ago? Maarten van de Guchte, director of the Museum of Art and Cummer Gardens at Riverside in the us believes it can. "Look at the yellow sunset light reflected in the ponds,' he says pointing to a brightly coloured area painted by the American artist Thomas Moran exactly 100 years ago. In this landscape people usually see life and beauty, but scientists in Greece see the secret to studying pollution.

A team at the National Observatory of Athens looked at 554 paintings of sunsets from 1500 to 1900. The works were selected from across the world were similar to Moran's. Paintings made in the years after volcanoes erupted showed higher amounts of dust in the sky.

But an artist's brush as a scientific instrument? Van de Guchte says why not. "These guys would sit there for hours, watch the sky, see how the wind, sun, the rain, would change that sky. So, we get a realistic picture of the weather conditions centuries ago,' he says.