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 |  |  | FRONTIERS
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 |  |  | Frontiers explores new ideas in science, meeting the researchers who see the world through fresh eyes and challenge existing theories - as well as hearing from their critics. Many such developments create new ethical and moral questions and Frontiers is not afraid to consider these. [email protected] |  |  |  |  | LISTEN AGAIN 30 min |  |  | |
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Manmade greenhouse gases affect global warming - a well known fact. But how much does the Sun contribute to this effect?
Solar activity The Sun's activity varies according to many different cycles.
The longest cycles are on a millennial scale and account for events such as ice ages and the extinction of the dinosaurs.
Cosmic rays The Sun releases electrically charged particles which blow cosmic rays away from the Earth.
When solar activity is low, fewer particles are released and more cosmic rays reach the Earth. |  |  |  | | Cloud formation Henrik Svensmark of the Danish Space Research Institute hopes to prove that these cosmic rays promote cloud formation.
He suggests that more clouds means the Earth's temperature actually falls.
Peter Evans explores the theory and visits the laboratory where the experiment is being prepared
This is the last in the current series of Frontiers. |  |  |  RELATED LINKS Danish Space Research Institute Henrik Svensmark Rutherford Appleton Laboratory CERN (William) Herschel Museum BBCi Science
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