If white Christmases in Ireland are as rare as we discovered yesterday, is it not strange that the cards we send each other at that time of year invariably show a landscape covered with several feet of snow?
Skaters disport themselves on frozen ponds, buglers bugle from snow-entrenched stagecoaches, and little robins search for crumbs in the very cruellest blizzards.
And yet our typical Irish Christmas is wet and windy, or bright and frosty; snow may appear now and then, but it is rare. Where, then, did these romantic notions come from?
The perennial white Christmas is not entirely a figment of the artist's imagination. Most of our ideas about Yuletide are based on traditions from the 18th and 19th centuries, and at that time the white Christmas was a harsh reality. Europe was in the middle of the Little Ice Age, and average temperatures were a degree or more lower than they are now.
There is a number of reasons why our climate should vary over the centuries.
Slight changes in the earth's orbit affect our distance from the sun at any given time of the year; the inclination of the earth's axis changes, which affects the amount of solar energy absorbed by our planet, as opposed to being reflected back out to space; and during a period of high volcanic activity, dust obscures the sky and prevents solar radiation from reaching the ground.
Whatever the reason, the Little Ice Age in the northern hemisphere began around 1450 and lasted until near the end of the last century, reaching its peak in the freezing decades of the 1690s. The summers were short and cool, the winters long and severe, and white Christmases were the norm rather than the exception.
In modern Ireland, when snow occurs in any quantity, it is much more likely to arrive in January or February than in December. White Christmases this century have been comparatively rare, and by all accounts in the next millennium they may be rarer still.
But I suppose we should also remember the concept of a white Christmas is very much American, and in parts of the US white Christmases are two a penny.
It is no wonder, for instance, that Dickensian Christmases are cold and white. Of the first nine Christmases of Charles Dickens's life, between 1812 and 1820, no fewer than six were white.
The decade from 1810 to 1820 was the coldest in England for more than a century, and no doubt set the scene for the young author for the rest of his life. Our experience nowadays is certainly less picturesque, but more amenable.