May 19, 2013 | 02:04 PM (BD Time)
19 May, 2013 Sunday
Ultraviolet light shone on cold winter conundrum
BBC Online :
Recent cold winters that brought chaos to the UK and other places in northern Europe may have their roots in the Sun's varying ultraviolet emissions. The latest satellite data shows the UV output is far more changeable than scientists had previously thought. A UK scientific team now shows in Nature Geoscience journal how these changes lead to warmer winters in some places and colder winters in others. The researchers emphasise there is no impact on global warming. The Sun has recently been in a quiet phase of its regular 11-year cycle, which co-incided with three years in which the UK, along with other places in northern Europe and parts of the US, experienced cold conditions unusual in the recent record.
But unusually warm weather was felt both further south, around the Mediterranean Sea, and further north in Canada and Greenland. "The key point is that this effect is a change in the circulation, moving air from one place to another, which is why some places get cold and others get warm," said Adam Scaife, one of the researchers on the paper, who heads the UK Met Office's Seasonal to Decadal Prediction team. "It's a jigsaw puzzle, and when you average it up over the globe, there is no effect on global temperatures," he told BBC News. The recent revelations on the Sun's ultraviolet variability come from a Nasa satellite called the SOlar Radiation and Climate Experiment (SORCE), launched in 2003.
Sun imaged in ultraviolet The Sun's ultraviolet output varies more with overall activity than had been suspected
Among its instruments is the Spectral Irradiance Monitor (SIM), which analyses the Sun's output at frequencies in the infrared, visible and ultraviolet parts of the spectrum. SIM is giving scientists a detailed picture of how the Sun's ultraviolet emissions vary over its regular 11-year cycle of waxing and waning energy; and it suggests the UV variation is about five times larger than had been inferred from previous observations.
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