Cold winters in recent years that have brought so much trouble to many European countries, may be related to variability in solar ultraviolet radiation.
According to recent data from satellites, the fluctuations in the level of UV radiation is much greater than believed.
A group of British geophysicists published in the journal Nature Geoscience article about how such fluctuations can lead to warmer winters in some parts of the globe, and to colder - in the others. The researchers emphasize that their data are not directly related to global warming.
Sun in recent years was in the quiet phase of its 11-year cycle that coincided with an unusually cold winters in the last three years in Britain, Northern Europe and the USA. In the southern latitudes, such as the Mediterranean, as well as at high latitudes in northern Canada and Greenland observed unusually warm weather.
These data were obtained by U.S. satellite SORCE (Solar Radiation and Climate Experiment),launched in 2003.
Among the devices installed on it is the registrar of oscillations of solar radiation, which analyzes light emission in the infrared, visible and ultraviolet portions of the spectrum.
According to the registrar, the fluctuations of UV radiation in recent years is five times higher than previously observed.
Retreating of Cold?
Fluctuations in the level of ultraviolet radiation from the Sun were much greater than scientists thought.
Geophysicists have entered the data obtained from satellite SORCE, to a computer model of the global climate used by the British Meteorological Service. The simulation results confirmed the hypothesis that variations in solar ultraviolet radiation affects the temperature distribution in the troposphere and stratosphere.
Ultraviolet radiation is absorbed by the ozone layer in the stratosphere, so on the lowest point of the solar activity cycle stratosphere cools down faster. This, in turn, leads to a change in the rate of airflow in the troposphere, including the air flow that circulates in the polar regions of the Northern Hemisphere.
As a result, air movement from west to east is reduced, and the cold air from the north of Siberia begins to increasingly influence the weather in Britain and North Europe.
However, it is not clear how accurate is the data obtained from satellite SORCE. Scientists tend to believe them, but marked variations are so large that they would prefer to get confirmation from other sources.
If the hypothesis of the influence of ultraviolet radiation fluctuations is correct, then in the next few years, winter in the Northern Europe will be softer, because there comes a new 11-year cycle of solar activity.
In addition to this cycle there are other, more extensive cyclical changes in the sun. For example, from 1645 to 1715, astronomers have noted the so-called Maunder minimum, when on the Sun were almost no sunspots.
The period of these observations coincided with a general cooling of climate in the Northern Hemisphere, which was called the Little Ice Age.