Relevant

1 Dec 2010:  In the mid-1990s, Henrik Svensmark and others at the Danish National Space Center developed the theory that variations in sunspot activity caused variations in Earth's climate. Svensmark pointed out that low-level cloudiness closely tracked the level of cosmic rays measured at Earth's surface. That is, the higher the level of cosmic rays, the more low-level clouds. It has been known for many years that the received level of cosmic rays is inversely related to sunspot activity on our sun. Svensmark proposed that sunspot activity varied the strength of the solar wind reaching the Earth, affecting the level of cosmic rays that entered our atmosphere, affecting low-level cloudiness, which then changed Earth's climate. His theory is a natural alternative to the IPCC's assertion that man-made greenhouse gas emissions are the dominant cause of global warming.

In November, an article was pubished in the Journal of Atmospheric Chemistry and Physics that supports Svensmark's theory. Laken, Kniveton, and Frogley, researchers from England and Spain, found a strong correlation between mid-latitude cloud changes and cosmic ray flux. See an excellent discussion by Anthony Watts here.