Solar surprises raise questions for climate models
Solar surprises raise questions for climate models
Oct 6 03:06 PM US/Eastern
This August 2010 image, courtesy of NASA's Solar and Heliospheric Observato...
Scientists found that a decline in the Sun's activity did not lead as expected to a cooling of the Earth, a surprise finding that could have repercussions for computer models on climate change.
The Sun's activity is known to wax and wane over 11-year cycles, which means that in theory the amount of radiation reaching Earth declines during the "waning" phase.
The new study was carried out between 2004 and 2007 during a solar waning phase.
The amount of energy in the ultraviolet part of the energy spectrum fell, the researchers found.
But, contrary to expectation, radiation in the visible part of the energy spectrum increased, rather than declined, which caused a warming effect.
The investigation, based mainly on satellite data, is important because of a debate over how far global warming is attributable to Man or to natural causes.
Climatologists say that warming is overwhelmingly due to man-made greenhouse gases -- invisible carbon emissions from coal, gas and coal that linger in the atmosphere and trap solar heat.
But a vocal lobby of sceptics say that this is flawed or alarmist, and point out that Earth has known periods of cooling and warming that are due to variations in the Sun's output.
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