Low solar activity is expected to cause the winter jet stream to bring bitterly cold Arctic air.
GLOBAL CLIMATE is warming, with 2010 expected to go down as yet another record year. You can count on our winters being colder than usual, however, at least for the next few years.
“There is a difference between global climate and regional climate, and there is a very peculiar thing we are finding about the European climate,” says Prof Mike Lockwood of the University of Southampton and the Rutherford Appleton Laboratory. Colder winters are expected because at the moment solar activity is very low.
Solar activity, in this case, does not mean direct heat or light from the sun but the energy emitted from the solar surface by sunspots. “What we are finding is that Europe and western Asia are particularly prone to solar influences, especially in winter,” Lockwood says. “What we are seeing is much cooler winters if solar activity is low.”
Last winter was particularly cold here and on the Continent, and low-temperature records were set.
Lockwood, who is Southampton’s professor of space and climate physics in the school of mathematical and physical sciences, believes we will see more of the same this winter. Climate change naysayers argue that temperature changes come down to a weakening or strengthening sun, but in fact Eurasia’s colder winters will be triggered by the jet stream, Lockwood explains. It is a phenomenon known as “set stream blocking”.
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Sometimes the normal winter flow of the high-altitude jet stream “gets kinked into a reverse S-shape”, says Lockwood. “What happens in a blocking event is the normal flow changes, the warm westerlies get disrupted and we get cold Arctic air from the north and east.”
This in turn changes the weather we see on the ground. “Although the jet stream is very high up it is known to direct weather patterns further down.”
The thing that gets the jet stream into a winter twist is none other than the sun, but only when it is not very active.
“There is no doubt that the frequency of those blocking events in winter is higher when solar activity is low,” says Lockwood. “What was a slight surprise is that the sun was changing the jet stream, but only when the jet stream has travelled across the Atlantic and begins hitting land over Europe.”
Lockwood believes that the phenomenon may have been responsible for the “Little Ice Age” in Europe, a time between about 1650 and 1700 when people skated on the frozen Thames. During that time astronomers noted that there were no sunspots for 50 years, and Europe became extra cold.
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