With December this year having brought us nearly every type of winter weather possible, thoughts have now turned towards Christmas, and whether it will be white again this year.
The reality about Christmas weather in Scotland, however, is that it is much more likely to be damp, wet or windy, rather than having the snow lying, deep and crisp and even. And this year, the weather forecasts for Christmas Day are now clearly pointing towards a more typical mild, wet and windy festive season.
What are the chances of getting a white Christmas in any given year in Scotland? The answer to this, of course, depends on where you live. Looking at the long-term statistics available from the Met Office (see list), in the main cities the probability of a White Christmas ranges from about one year in six in Aberdeen, to one year in ten or 12 for Edinburgh and Glasgow respectively, to less than one year in 30 on the Ayrshire coast. It is only in the higher towns of Highlands, for example Braemar, that the chance of a white Christmas increases to nearly once every two years (i.e. a 50% chance).
Statistical chance of a White Christmas
Glasgow - 1 year in 12
Edinburgh - 1 year in 10
Aberdeen - 1 year in 6
Inverness - 1 year in 8
Stornoway - 1 year in 15
Lerwick - 1 year in 5
Braemar - 1 year in 2
Prestwick - less than 1 year in 30
This brings us to the question of why recent winters have been so snowy.
The statistics do indeed confirm that recent Decembers have been snowier than the 20th century average.
Indeed, December has been the only winter month that has ‘bucked’ the general warming trend. In 1995, there was a record cold spell at Christmas, when the lowest ever air temperature recorded in Scotland (-27.2°C) was equalled at Altnaharra.
December 2000 also brought cold and snowy weather between Christmas and New Year.
Two years ago, December 2009 brought much snow and ice, and of course how can we forget December 2010?
It was one of the coldest and snowiest Decembers ever recorded in Scotland. This means that we have had had two white Christmases in a row in 2009 and 2010.
Recent research by Prof. Mike Lockwood and colleagues at the University of Reading have suggested that there is a link between cold winters in Europe and ‘quiet’ phases of the solar sunspot cycle; it so happens that we are in a quiet phase just now.
Other researchers point to the remarkable loss of sea-ice in the Arctic Ocean over recent years (there is now 30 to 40% less sea-ice during the late summer and autumn due to global warming).
Such a huge difference in sea-ice distribution causes more water to evaporate from the open sea surface and is sure to change the atmospheric circulation. Others say the increased volcanic activity of recent years has upset global weather patterns.
But whatever the weather may be this Christmas, white, wet or wild, may you have a joyful and peaceful festive season!
By Dr. Edward Graham, University of the Highlands and Islands