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![Science](/staticarchive/ca3a3b42242b39fd4f2de217c70ee897ccf8796b.gif)
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Go to the Listen Again page | ![](/staticarchive/e625f03f6d44fa4bee51ee3880a504df1ec7ca17.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) |
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![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | Frontiers explores new ideas in science, meeting the researchers whoÌýsee the world through fresh eyes and challenge existing theories - as well asÌýhearing fromÌýtheir critics. ManyÌýsuch developments create new ethical and moral questions and Frontiers is not afraid to consider these. radioscience@bbc.co.uk | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | LISTEN AGAIN![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) Ìý30 min | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | |
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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 variesÌýaccording toÌýmany different cycles.
The longest cycles are on a millennial scale and account for events such as ice ages and the extinction of the dinosaurs.Ìý
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. | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![London skyline](/staticarchive/f39123b7bc4763fd4ac7e79c1be8e1e014d0d52c.jpg) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | | Cloud formation Henrik Svensmark of the Danish Space Research Institute hopes to prove that these cosmic rays promote cloud formation.Ìý
He suggests that more clouds means the Earth's temperature actuallyÌýfalls.Ìý
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. | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) | ![](/staticarchive/317496a096d6c86486a71d4521994bcd171a6bb3.gif) RELATED LINKS
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