The winter solstice

  • The winter solstice
    21.12.2010 16:50

    December 21-22 marks the winter solstice in the northern hemisphere when the Earth’s axial tilt is farther from the sun, and from here on the nights in Britain will get shorter and the days longer.

    There is an old saying applied to this part of winter that states something like “as the days grow longer the cold gets stronger”.

    It would be worrying if the rest of the winter were to become even colder than the extremes we have experienced since late November, although it is certainly not impossible. It is not an apothegm that always comes true but why should it so often be the case when we are receiving more sunshine by the day? The average temperature in January is certainly lower than that in December.

    The answer lies in the oceans. During the winter months solar radiation gives us a feeble amount of warmth, which is why locations locked near the middle of their continents are so very cold during the winter – places like Irkutsk and Oymyakon in Siberia, for example, where the temperature regularly plunges below -60 or even -70 degrees Celsius.

    The UK “should” be a lot colder for its latitude during the winter but usually benefits from the influence of the relatively mild seas by which it is surrounded. It has been so cold in the past three to four weeks, however, because we have had winds from the cold Continent or straight out of the Arctic so often.

    The sea reacts a lot more slowly than the land to the change in seasons and cooling and warming of the atmosphere, so that it is at its warmest in early autumn and coldest in late winter and early spring. Ordinarily, therefore, it would have more of a cooling effect later in the winter but more winds from the Atlantic would give us a milder second half of winter than the first half.

    These are not ordinary times, though – December 2010 is going to go down as one of the coldest on record unless it warms up spectacularly. After a quiet and very cold Christmas Day, with fog in places, it does look like becoming milder between Christmas and New Year with rain on the way, preceded by more snow. But not so warm as to put much of a dent in the statistics.

    By: Stephen Davenport