Artistic eye on the sky


NOW that the hallowed doors of the National Gallery are open once again, those so inclined will have the opportunity of casting a weather eye over the enhanced display.

Over the centuries, artists have chronicled the fauna and flora of their times, the furniture and architecture then in fashion, and the musical instruments and games that served as entertainment. But has John Constable wrote many years ago, "the landscape painter who does not make his" "skies a very material part of his compositions, neglects to avail himself of one of hiss greatest aids." Paintings are, therefore a fruitful source of information for meteorologists in the constant quest to reconstruct the climate of the centuries gone by.

Fifty three per cent of paintings contain some meteorological information. Not a lot of people know that, butt the statistic is firmly based on an exhaustive survey carried out some years ago by an American professor covering 50 major art galleries in the United States and Europe. He analysed 12,000 paintings in all, ranging in the dates of their execution from 1400 to 1967, and he estimated the cloud amounts and visibilities they showed.

Some of the findings are obvious and meteorologically predictable. Average cloud amount, for example, decreases with the latitude of the scene portrayed those of northern countries feature cloudy skies, whereas a large proportion of paintings done in Spain or Italy are entirely free of cloud. But there have been subtle changes with the centuries, which mirror well documented changes in the climate of the northern hemisphere.

From the 10th century to the end of the 15th, the average temperature over Europe and North America was significantly higher than it is now, and climatic conditions here correspondingly benign. From around 1500 to about 1850, however, there occurred what is called the Little Ice Age winters were long and severe, and summers, in general, were cool, changeable and wet. These developments it seems, can be deduced from contemporary paintings.

The average cloudiness in paintings of the 15th century, according to the survey, was about 30 per cent, while painted skies of the 1600s show an average cloud cover of four fifths. Skies became clearer again in the late 19th and early 20th centuries, with the average cloudiness dropping to some 70 per cent. The measure, of course, is very crude indeed, and some of the changes are dictated, not by weather, but by variations in artistic taste and fashion. Nonetheless, the findings echo and therefore to some extent confirm the known changes in the global climate.