We all grumble about the weather. Sometimes when it gets really bad we ask ourselves if this is the beginning of another ice age.
Now scientists are telling us this is no joke; it is a question which needs a serious answer.
Britain’s top weather historian, Hubert Lamb of the British Meteorological Office at Bracknell, Berkshire, has for years been studying weather records stretching as far back as ancient China.
He says there has been a dramatic turn-around in northern hemisphere climate since 1950. “The first half of this century must be regarded as the mildest period of our climate for a very long time, and since 1950 we have already had a very abrupt throwback to conditions as they were before.”
In the past few years all summers have been below average temperature. Only 1967 produced a mean temperature a fraction above average. Arguments of this kind always depend on the time span being considered. The German scientist Theo Lobsack thinks we have lived through a few decades in which the earth was warming up, but this is only a tiny interval in a much longer period of gradual cooling.
There were periods hundreds of millions of years ago when there was no ice at all even at the poles and Europe had tropical vegetation, but at other times all Britain was covered by ice.
Within the last million years there have been four ice ages, falling at intervals of about a hundred thousand years, each lasting around 40,000 years.
The last such age, when sheets of ice reached the Alps, was probably at its peak 18,000 years ago. But there were no weather records in Britain before 55 BC and we have to read the fossils for evidence.
In 500 BC the weather was so bad that the Alpine passes, which had been in use for 1,300 years, were closed. But by 664 AD the first reliably known hot summer was recorded.
By the year 1000 AD Norsemen were sailing between Iceland and Greenland throughout the year without the hazard of ice floes and Greenland’s Baffin Bay was free of ice. It was getting warmer. In the 12th century there were many vineyards in Southern England.
But by 1300 it had become very cold, with a much shorter growing season for crops resulting in harvest failures and famines in Europe. In 1520 the Swedish armies marched across the Baltic Sea on ice and in 1537 King Henry VIII rode a carriage down the frozen Thames.
Even more extraordinary, Queen Elizabeth I held winter fairs on the Thames. The ice was so thick that bonfires could be lit on it and whole oxen roasted.
Hubert Lamb has a theory that there is a 200-year cycle in Britain’s weather. The good weather comes when the south westerlies are prevalent, bringing warmer air from the Atlantic. These western winds carry cyclonic disturbances away from Britain into the polar regions.
The best years have fallen in the 1340s, the 1520-30s, the 1730s and the 1920-30s. Hubert Lamb has noticed these dates fall early in the century every 200 years or so the years that follow bring much lower westerly wind frequencies.
As the westerlies tire, the polar air cap expands and the cold Arctic air pushes south. This was illustrated vividly last year, when the polar anti-cyclonic system came as far south as Scandinavia and Scotland, giving them a good dry summer, but it probably means long cold winters in the future too.
The westerlies which blew 30 per cent of the time in the first half of this century have fallen away in recent years to 20 per cent of the time. What is more they are blowing further south over France, leaving Britain in the cold! With the westerlies in retreat, the bad weather comes. From 1550 to 1700 was the coldest period that Europe has ever known since 8,000 BC.
This was the period in which the famous Dutch winter landscapes were painted and the Alpine passes closed once again.
In 1740 came the longest freeze Britain has ever recorded (until the winter of 1962-63). But towards the end of the 18th century things were on the mend again, bringing really hot summers, but rather severe winters.
Dickens was the man really responsible for giving the British weather such a bad reputation. His descriptions of the Christmas snow and perishing winds were characteristic of the 1812-20 period (the latter part of which he would have known as a boy).
Source: Alan Rake (London), The Canberra Times