The conjectured mechanism connecting GCR flux to low cloud formation received experimental confirmation in the recent laboratory experiments of Svensmark et al. (2006) and Svensmark (2007), which demonstrated that cosmic rays trigger formation of water droplet clouds.

Le Mouel et al. (2005) showed a strong correlation of geomagnetic indices and global temperature over the last century with some departure after 1990 perhaps indicating anthropogenic effects.

Shaviv (2004) found that when including the changes in cosmic rays over the last century, the total solar influence could be responsible for 0.47C (±0.19C) or roughly 77% of the total reported warming.

This issue is yet to be resolved but may indeed turn out to be an important solar climate link considering the plethora of correlations of climate trends with the GCR proxies (e.g. cosmogenic nuclides; Solanki et al., 200x), over a multitude of time scales, as compiled in Veizer (2005) and Scherer et al. (2006).