In this YouTube video Henrik Svensmark and colleagues demonstrate the links between Solar Activity and Climate, arising through interaction of the Solar magnetic field and Solar Wind with galactic Cosmic Rays. A weaker field lets more Cosmic Rays through to our atmosphere. More Cosmic Rays form more ions that nucleate low level clouds. More low level clouds reflect more Solar radiation back into space cooling the planet.
Source: Watts Up With That at https://wattsupwiththat.com/2013/09/04/svensmarks-cosmic-ray-theory-of-clouds-and-global-warming-looks-to-be-confirmed/