Tuesday 14 December 2010, 10:32
Because of the cold weather, some people are saying "so much for global warming" which is understandable but this is far from the case. Climate and weather, although interlinked, are separate things.
Mark Twain, American humorist, writer and lecturer once said "Climate is what we expect and weather is what we get!"
Weather is something which changes by the hour and from day to day, while climate is weather averaged over a long period of time - normally 30 years.
The cold weather we're experiencing now doesn't mean that that global warming has suddenly stopped or gone away.
Far from it. It's just that we're colder than normal at the moment and other parts of the world are warmer than usual which is all part of the natural variation in weather.
Normally, the jet stream, which is a ribbon of strong winds high in the atmosphere (around 30,000 feet), would steer areas of low pressure in from the Atlantic bringing us spells of wet and windy weather but sometimes the jet stream gets diverted.
High pressure forms to the north and east of Britain and instead of mild south westerly winds - we end up with winds from the north or east, drawing in very cold air from the Arctic, Scandinavia and sometimes Siberia.
These winds pick-up moisture as they cross the sea and dump it as snow. Sometimes the atmosphere can get stuck in a rut and "blocks of air" can form.
These blocks are natural and can be difficult to shift and can last from a few days to a few weeks before finally breaking down.
Depending on which side of the block you are on - it can either be very warm or exceptionally cold.
Recently it's been colder in Wales than on the south coast off Greenland because of the shape and position of the jet stream. In Russia this summer however, a blocking high led to a devastating heat wave and drought.
Since 1981 and 1982 many winters have been fairly mild in Wales until recently with little if any snow before Christmas.
Another thing to bear in mind, is that although the overall trend in Britain maybe towards a warmer climate, that does not rule out wet summers in the future or cold, snowy winters.
Indeed, some forecasters are now saying we could be entering a new phase or cycle, something which is separate from climate change.
This cycle may last several years or even decades and if right, it could mean that colder winters may be something we have to get used to.
Time will tell of course but whether you believe in climate change or not, one thing is certain, the weather will never stop being a talking point in Britain wherever you are; at the bus stop, in work or down the pub!
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